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  • Figure 2.1 John Dalton (1766-1844)
  • Figure 2.1 John Dalton (1766-1844)
  • Figure 2.1 John Dalton (1766-1844)
  • Figure 2.1 John Dalton (1766-1844)
  • Figure 2.4
  • Figure 2.4
  • Figure 2.5
  • Figure 2.5
  • Figure 2.8
  • Figure 2.9
  • Figure 2.10
  • Figure 2.11
  • Figure 2.12
  • Table 2.1
  • Figure 2.13
  • Transcript

    • 1. Chemistry In this science we study matter and the changes it undergoes. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 2. MatterWe define matter as anything that has massand takes up space. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 3. Matter• Atoms are the building blocks of matter. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 4. Matter• Atoms are the building blocks of matter.• Each element is made of the same kind of atom. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 5. Matter• Atoms are the building blocks of matter.• Each element is made of the same kind of atom.• A compound is made of two or more different kinds of elements. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 6. States of Matter Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 7. Classification of Matter Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 8. Classification of Matter Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 9. Classification of Matter Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 10. Classification of Matter Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 11. Classification of Matter Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 12. Classification of Matter Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 13. Classification of Matter Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 14. Classification of Matter Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 15. Classification of Matter Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 16. Classification of Matter Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 17. Properties and Changes of Matter Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 18. Types of Properties• Physical Properties… – Can be observed without changing a substance into another substance. • Boiling point, density, mass, volume, etc.• Chemical Properties… – Can only be observed when a substance is changed into another substance. • Flammability, corrosiveness, reactivity with acid, etc. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 19. Types of Properties• Intensive Properties… – Are independent of the amount of the substance that is present. • Density, boiling point, color, etc.• Extensive Properties… – Depend upon the amount of the substance present. • Mass, volume, energy, etc. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 20. Types of Changes• Physical Changes – These are changes in matter that do not change the composition of a substance. • Changes of state, temperature, volume, etc.• Chemical Changes – Chemical changes result in new substances. • Combustion, oxidation, decomposition, etc. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 21. Chemical ReactionsIn the course of a chemical reaction, thereacting substances are converted to new Mattersubstances. And Measurement © 2009, Prentice-Hall, Inc.
    • 22. CompoundsCompounds can bebroken down intomore elementalparticles. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 23. Separation of Mixtures Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 24. Filtration In filtration solid substances are separated from liquids and solutions. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 25. Distillation Distillation uses differences in the boiling points of substances to separate a homogeneous mixture into its components. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 26. ChromatographyThis technique separates substances on thebasis of differences in solubility in a solvent. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 27. What do these countries have in common? US, Liberia and Burma Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 28. What do these countries have in common? US, Liberia and Burma• They use the imperial system Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 29. View of Countries using Metric USA Berma Liberia Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 30. Units ofMeasurement Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 31. SI Units• Système International d’Unités• A different base unit is used for each quantity. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 32. Metric SystemPrefixes convert the base units into units thatare appropriate for the item being measured. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 33. Volume• The most commonly used metric units for volume are the liter (L) and the milliliter (mL). – A liter is a cube 1 dm long on each side. – A milliliter is a cube 1 cm long on each side. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 34. Uncertainty inMeasurement Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 35. Uncertainty in MeasurementsDifferent measuring devices have differentuses and different degrees of accuracy. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 36. Uncertainty in Measurements Different measuring devices have different uses and different degrees of accuracy.1 ml Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 37. Uncertainty in MeasurementsDifferent measuring devices have differentuses and different degrees of accuracy. 0.1 ml Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 38. Accuracy versus Precision• Accuracy refers to the proximity of a measurement to the true value of a quantity.• Precision refers to the proximity of several measurements to each other. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 39. Significant Figures• The term significant figures refers to digits that were measured.• When rounding calculated numbers, we pay attention to significant figures so we do not overstate the accuracy of our answers. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 40. Significant Figures1. All nonzero digits are significant.2. Zeroes between two significant figures are themselves significant.3. Zeroes at the beginning of a number are never significant.4. Zeroes at the end of a number are significant if a decimal point is written in the number. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 41. Significant Figures• When addition or subtraction is performed, answers are rounded to the least significant decimal place.• When multiplication or division is performed, answers are rounded to the number of digits that corresponds to the least number of significant figures in any of the numbers used in the calculation. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 42. Temperature By definition temperature is a measure of the average kinetic energy of the particles in a sample. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 43. Temperature • In scientific measurements, the Celsius and Kelvin scales are most often used. • The Celsius scale is based on the properties of water. – 0°C is the freezing point of water. – 100°C is the boiling point of water. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 44. Temperature • The Kelvin is the SI unit of temperature. • It is based on the properties of gases. • There are no negative Kelvin temperatures. • K = °C + 273.15 Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 45. Temperature • The Fahrenheit scale is not used in scientific measurements. ∀ °F = 9/5(°C) + 32 ∀ °C = 5/9(°F − 32) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 46. DensityDensity is a physical property of a substance. m d= V Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 47. Dimensional Analysis • We use dimensional analysis to convert one quantity to another. • Most commonly dimensional analysis utilizes conversion factors (e.g., 1 in. = 2.54 cm) 1 in. 2.54 cm or 2.54 cm 1 in. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 48. Dimensional AnalysisUse the form of the conversion factorthat puts the sought-for unit in thenumerator. desired unit Given unit × = desired unit given unitConversion factor Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 49. Dimensional Analysis• For example, to convert 8.00 m to inches, – convert m to cm – convert cm to in. 100 cm 1 in. 8.00 m × × = 315 in. 1m 2.54 cm Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 50. Atomic Theory of MatterThe theory that atoms are the fundamentalbuilding blocks of matter reemerged in the early19th century, championed by John Dalton. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 51. Daltons PostulatesEach element is composed of extremely smallparticles called atoms. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 52. Daltons PostulatesAll atoms of a given element are identical to oneanother in mass (?) and other properties, but theatoms of one element are different from theatoms of all other elements. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 53. Daltons PostulatesAtoms of an element are notchanged into atoms of a differentelement by chemical reactions;atoms are neither created nordestroyed in chemical reactions. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 54. Dalton’s PostulatesCompounds are formed when atoms ofmore than one element combine; agiven compound always has the samerelative number and kind of atoms. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 55. Law of Constant Composition Joseph Proust (1754–1826)• This is also known as the law of definite proportions.• It states that the elemental composition of a pure substance never varies. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 56. Law of Conservation of MassThe total mass of substances present atthe end of a chemical process is thesame as the mass of substancespresent before the process took place. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 57. The Electron• Streams of negatively charged particles were found to emanate from cathode tubes.• J. J. Thompson is credited with their discovery (1897). Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 58. The ElectronThompson measured the charge/mass ratioof the electron to be 1.76 × 108 coulombs/g. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 59. Millikan Oil Drop ExperimentOnce the charge/massratio of the electronwas known,determination of eitherthe charge or the massof an electron wouldyield the other. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 60. Millikan Oil Drop ExperimentRobert Millikan(University of Chicago)determined the chargeon the electron in1909. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 61. Radioactivity• Radioactivity is the spontaneous emission of radiation by an atom.• It was first observed by Henri Becquerel.• Marie and Pierre Curie also studied it. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 62. Radioactivity• Three types of radiation were discovered by Ernest Rutherford: α particles β particles γ rays Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 63. The Atom, circa 1900 • The prevailing theory was that of the “plum pudding” model, put forward by Thompson. • It featured a positive sphere of matter with negative electrons imbedded in it. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 64. Discovery of the Nucleus Ernest Rutherford shot α particles at a thin sheet of gold foil and observed the pattern of scatter of the particles. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 65. The Nuclear AtomSince some particleswere deflected atlarge angles,Thompson’s modelcould not be correct. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 66. The Nuclear Atom• Rutherford postulated a very small, dense nucleus with the electrons around the outside of the atom.• Most of the volume of the atom is empty space. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 67. Other Subatomic Particles• Protons were discovered by Rutherford in 1919.• Neutrons were discovered by James Chadwick in 1932. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 68. Subatomic Particles• Protons and electrons are the only particles that have a charge.• Protons and neutrons have essentially the same mass.• The mass of an electron is so small we ignore it. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 69. Symbols of ElementsElements are symbolized by one or twoletters. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 70. Atomic NumberAll atoms of the same element have the samenumber of protons:The atomic number (Z) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 71. Atomic MassThe mass of an atom in atomic mass units(amu) is the total number of protons andneutrons in the atom. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 72. Isotopes• Isotopes are atoms of the same element with different masses.• Isotopes have different numbers of neutrons. 11 12 13 14 6 C 6 C 6 C 6 C Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 73. Atomic Mass Atomic and molecular masses can be measured with great accuracy with a mass spectrometer. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 74. Average Mass• Because in the real world we use large amounts of atoms and molecules, we use average masses in calculations.• Average mass is calculated from the isotopes of an element weighted by their relative abundances. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 75. Periodic Table • It is a systematic catalog of the elements. • Elements are arranged in order of atomic number. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 76. PeriodicityWhen one looks at the chemical properties ofelements, one notices a repeating pattern ofreactivities. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 77. Periodic Table• The rows on the periodic chart are periods.• Columns are groups.• Elements in the same group have similar chemical properties. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 78. GroupsThese five groups are known by their names. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 79. Periodic Table Nonmetals are on the right side of the periodic table (with the exception of H). Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 80. Periodic Table Metalloids border the stair-step line (with the exception of Al, Po, and At). Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 81. Periodic Table Metals are on the left side of the chart. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 82. Chemical Formulas The subscript to the right of the symbol of an element tells the number of atoms of that element in one molecule of the compound. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 83. Chemical Formulas Molecular compounds are composed of molecules and almost always contain only nonmetals. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 84. Diatomic MoleculesThese seven elements occur naturally asmolecules containing two atoms. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 85. Types of Formulas• Empirical formulas give the lowest whole-number ratio of atoms of each element in a compound.• Molecular formulas give the exact number of atoms of each element in a compound. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 86. Types of Formulas • Structural formulas show the order in which atoms are bonded. • Perspective drawings also show the three-dimensional array of atoms in a compound. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 87. Ions• When atoms lose or gain electrons, they become ions. – Cations are positive and are formed by elements on the left side of the periodic chart. – Anions are negative and are formed by elements Matter on the right side of the periodic chart. And Measurement © 2009, Prentice-Hall, Inc.
    • 88. Ionic BondsIonic compounds (such as NaCl) aregenerally formed between metals andnonmetals. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 89. Writing Formulas• Because compounds are electrically neutral, one can determine the formula of a compound this way: – The charge on the cation becomes the subscript on the anion. – The charge on the anion becomes the subscript on the cation. – If these subscripts are not in the lowest whole- number ratio, divide them by the greatest common Matter factor. And Measurement © 2009, Prentice-Hall, Inc.
    • 90. Common Cations Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 91. Common Anions Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 92. Inorganic Nomenclature• Write the name of the cation.• If the anion is an element, change its ending to -ide; if the anion is a polyatomic ion, simply write the name of the polyatomic ion.• If the cation can have more than one possible charge, write the charge as a Roman numeral in parentheses. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 93. Patterns in Oxyanion Nomenclature • When there are two oxyanions involving the same element: – The one with fewer oxygens ends in -ite. • NO2− : nitrite; SO32− : sulfite – The one with more oxygens ends in -ate. • NO3− : nitrate; SO42− : sulfate Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 94. Patterns in Oxyanion Nomenclature• The one with the second fewest oxygens ends in -ite. – ClO2− : chlorite• The one with the second most oxygens ends in -ate. – ClO3− : chlorate Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 95. Patterns in Oxyanion Nomenclature• The one with the fewest oxygens has the prefix hypo- and ends in -ite. – ClO− : hypochlorite• The one with the most oxygens has the prefix per- and ends in -ate. – ClO4− : perchlorate Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 96. Acid Nomenclature • If the anion in the acid ends in -ide, change the ending to -ic acid and add the prefix hydro- . – HCl: hydrochloric acid – HBr: hydrobromic acid – HI: hydroiodic acid Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 97. Acid Nomenclature • If the anion in the acid ends in -ite, change the ending to -ous acid. – HClO: hypochlorous acid – HClO2: chlorous acid Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 98. Acid Nomenclature • If the anion in the acid ends in -ate, change the ending to -ic acid. – HClO3: chloric acid – HClO4: perchloric acid Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 99. Nomenclature of Binary Compounds • The less electronegative atom is usually listed first. • A prefix is used to denote the number of atoms of each element in the compound (mono- is not used on the first element listed, however) . Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 100. Nomenclature of Binary Compounds • The ending on the more electronegative element is changed to -ide. – CO2: carbon dioxide – CCl4: carbon tetrachloride Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 101. Nomenclature of Binary Compounds • If the prefix ends with a or o and the name of the element begins with a vowel, the two successive vowels are often elided into one. N2O5: dinitrogen pentoxide Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 102. Nomenclature of Organic Compounds• Organic chemistry is the study of carbon.• Organic chemistry has its own system of nomenclature. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 103. Nomenclature of Organic CompoundsThe simplest hydrocarbons (compoundscontaining only carbon and hydrogen) arealkanes. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 104. Nomenclature of Organic CompoundsThe first part of the names above correspondto the number of carbons (meth- = 1, eth- = 2,prop- = 3, etc.). Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 105. Nomenclature of Organic Compounds• When a hydrogen in an alkane is replaced with something else (a functional group, like -OH in the compounds above), the name is derived from the name of the alkane.• The ending denotes the type of compound. Matter – An alcohol ends in -ol. And Measurement © 2009, Prentice-Hall, Inc.
    • 106. Law of Conservation of Mass “We may lay it down as an incontestable axiom that, in all the operations of art and nature, nothing is created; an equal amount of matter exists both before and after the experiment. Upon this principle, the whole art of performing chemical experiments depends.” --Antoine Lavoisier, 1789 Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 107. Chemical EquationsChemical equations are conciserepresentations of chemical reactions. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 108. Anatomy of a Chemical EquationCH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 109. Anatomy of a Chemical EquationCH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)Reactants appear on the leftside of the equation. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 110. Anatomy of a Chemical EquationCH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)Products appear on theright side of the equation. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 111. Anatomy of a Chemical EquationCH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)The states of the reactants and productsare written in parentheses to the right of Matter Andeach compound. Measurement © 2009, Prentice-Hall, Inc.
    • 112. Anatomy of a Chemical EquationCH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g) Coefficients are inserted to balance the equation. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 113. Subscripts and Coefficients Give Different Information• Subscripts tell the number of atoms of each element in a molecule. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 114. Subscripts and Coefficients Give Different Information• Subscripts tell the number of atoms of each element in a molecule• Coefficients tell the number of Matter And molecules. Measurement © 2009, Prentice-Hall, Inc.
    • 115. Reaction Types Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 116. Combination Reactions • In this type of reaction two or more substances react to form one product.• Examples: – 2 Mg (s) + O2 (g) → 2 MgO (s) – N2 (g) + 3 H2 (g) → 2 NH3 (g) Matter – C3H6 (g) + Br2 (l) → C3H6Br2 (l) And Measurement © 2009, Prentice-Hall, Inc.
    • 117. Decomposition Reactions • In a decomposition one substance breaks down into two or more substances.• Examples: – CaCO3 (s) → CaO (s) + CO2 (g) – 2 KClO3 (s) → 2 KCl (s) + O2 (g) Matter – 2 NaN3 (s) → 2 Na (s) + 3 N2 (g) And Measurement © 2009, Prentice-Hall, Inc.
    • 118. Combustion Reactions • These are generally rapid reactions that produce a flame. • Most often involve hydrocarbons reacting with oxygen in the air.• Examples: – CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O (g) Matter – C3H8 (g) + 5 O2 (g) → 3 CO2 (g) + 4 H2O (g) And Measurement © 2009, Prentice-Hall, Inc.
    • 119. FormulaWeights Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 120. Formula Weight (FW)• A formula weight is the sum of the atomic weights for the atoms in a chemical formula.• So, the formula weight of calcium chloride, CaCl2, would be Ca: 1(40.1 amu) + Cl: 2(35.5 amu) 111.1 amu• Formula weights are generally reported for ionic compounds. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 121. Molecular Weight (MW)• A molecular weight is the sum of the atomic weights of the atoms in a molecule.• For the molecule ethane, C2H6, the molecular weight would be C: 2(12.0 amu) + H: 6(1.0 amu) 30.0 amu Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 122. Percent Composition One can find the percentage of the mass of a compound that comes from each of the elements in the compound by using this equation: (number of atoms)(atomic weight)% element = x 100 (FW of the compound) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 123. Percent CompositionSo the percentage of carbon in ethaneis… (2)(12.0 amu) %C = (30.0 amu) 24.0 amu = x 100 30.0 amu = 80.0% Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 124. Moles Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 125. Avogadro’s Number• 6.02 x 1023• 1 mole of 12C has a mass of 12 g. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 126. Molar Mass• By definition, a molar mass is the mass of 1 mol of a substance (i.e., g/mol). – The molar mass of an element is the mass number for the element that we find on the periodic table. – The formula weight (in amu’s) will be the same number as the molar mass (in g/mol). Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 127. Using MolesMoles provide a bridge from the molecularscale to the real-world scale. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 128. Mole Relationships• One mole of atoms, ions, or molecules contains Avogadro’s number of those particles.• One mole of molecules or formula units contains Avogadro’s number times the number of atoms or ions of each element in the compound. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 129. FindingEmpiricalFormulas Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 130. Calculating Empirical FormulasOne can calculate the empirical formula fromthe percent composition. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 131. Calculating Empirical FormulasThe compound para-aminobenzoic acid (you may haveseen it listed as PABA on your bottle of sunscreen) iscomposed of carbon (61.31%), hydrogen (5.14%),nitrogen (10.21%), and oxygen (23.33%). Find theempirical formula of PABA. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 132. Calculating Empirical FormulasAssuming 100.00 g of para-aminobenzoic acid, C: 61.31 g x 1 mol = 5.105 mol C 12.01 g 1 mol H: 5.14 g x = 5.09 mol H 1.01 g 1 mol N: 10.21 g x = 0.7288 mol N 14.01 g 1 mol O: 23.33 g x = 1.456 mol O 16.00 g Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 133. Calculating Empirical FormulasCalculate the mole ratio by dividing by the smallest numberof moles: 5.105 mol C: = 7.005 ≈ 7 0.7288 mol 5.09 mol H: = 6.984 ≈ 7 0.7288 mol 0.7288 mol N: = 1.000 0.7288 mol 1.458 mol O: = 2.001 ≈ 2 Matter 0.7288 mol And Measurement © 2009, Prentice-Hall, Inc.
    • 134. Calculating Empirical FormulasThese are the subscripts for the empirical formula: C7H7NO2 Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 135. Combustion Analysis• Compounds containing C, H and O are routinely analyzed through combustion in a chamber like this. – C is determined from the mass of CO2 produced. – H is determined from the mass of H2O produced. – O is determined by difference after the C and H have been determined. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 136. Elemental Analyses Compounds containing other elements are analyzed using methods analogous to those used for C, H and O. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 137. Stoichiometric CalculationsThe coefficients in the balanced equation givethe ratio of moles of reactants and products. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 138. Stoichiometric CalculationsStarting with themass of SubstanceA you can use theratio of thecoefficients of A andB to calculate themass of SubstanceB formed (if it’s aproduct) or used (ifit’s a reactant). Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 139. Stoichiometric Calculations C6H12O6 + 6 O2 → 6 CO2 + 6 H2OStarting with 1.00 g of C6H12O6…we calculate the moles of C6H12O6…use the coefficients to find the moles of H2O… Matterand then turn the moles of water to grams. And Measurement © 2009, Prentice-Hall, Inc.
    • 140. LimitingReactants Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 141. How Many Cookies Can I Make? • You can make cookies until you run out of one of the ingredients. • Once this family runs out of sugar, they will stop making cookies (at least any cookies you would want to eat). Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 142. How Many Cookies Can I Make? • In this example the sugar would be the limiting reactant, because it will limit the amount of cookies you can make. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 143. Limiting Reactants• The limiting reactant is the reactant present in the smallest stoichiometric amount. – In other words, it’s the reactant you’ll run out of first (in this case, the H2). Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 144. Limiting ReactantsIn the example below, the O2 would be theexcess reagent. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 145. Theoretical Yield• The theoretical yield is the maximum amount of product that can be made. – In other words it’s the amount of product possible as calculated through the stoichiometry problem.• This is different from the actual yield, which is the amount one actually produces and measures. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 146. Percent Yield One finds the percent yield by comparing the amount actually obtained (actual yield) to the amount it was possible to make (theoretical yield). Actual YieldPercent Yield = x 100 Theoretical Yield Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 147. Solutions • Solutions are defined as homogeneous mixtures of two or more pure substances. • The solvent is present in greatest abundance. • All other substances are solutes. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 148. Dissociation • When an ionic substance dissolves in water, the solvent pulls the individual ions from the crystal and solvates them. • This process is called dissociation. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 149. Dissociation • An electrolyte is a substances that dissociates into ions when dissolved in water. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 150. Electrolytes • An electrolyte is a substances that dissociates into ions when dissolved in water. • A nonelectrolyte may dissolve in water, but it does not dissociate into ions when it does Matter so. And Measurement © 2009, Prentice-Hall, Inc.
    • 151. Electrolytes andNonelectrolytes Soluble ionic compounds tend to be electrolytes. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 152. Electrolytes andNonelectrolytes Molecular compounds tend to be nonelectrolytes, except for acids and bases. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 153. Electrolytes• A strong electrolyte dissociates completely when dissolved in water.• A weak electrolyte only dissociates partially when dissolved in water. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 154. Strong Electrolytes Are…• Strong acids• Strong bases Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 155. Strong Electrolytes Are…• Strong acids• Strong bases• Soluble ionic salts Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 156. Precipitation ReactionsWhen one mixes ionsthat form compoundsthat are insoluble (ascould be predicted bythe solubilityguidelines), aprecipitate is formed. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 157. Metathesis (Exchange) Reactions • Metathesis comes from a Greek word that means “to transpose.” AgNO3 (aq) + KCl (aq) → AgCl (s) + KNO3 (aq) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 158. Metathesis (Exchange) Reactions • Metathesis comes from a Greek word that means “to transpose.” • It appears the ions in the reactant compounds exchange, or transpose, ions. AgNO3 (aq) + KCl (aq) → AgCl (s) + KNO3 (aq) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 159. Solubility of different compounds (NS = non soluble in water, S = soluble in water) Cl- Br- I- NO3- SO42- CO32- PO43-Li+ S S S S S S S SNa+ S S S S S S S SK+ S S S S S S S SMg2+ NS S S S S S NS NSCa2+ S S S S S S NS NSSr2+ S S S S S NS NS NSBa2+ S S S S S NS NS NSFe2+ NS S S S S S NS NSFe3+ NS S S S S S NS NSNi2+ NS S S S S S NS NSCu+ NS S S S S S NS NSCu2+ NS S S S S S NS NSAl3+ NS S S S S S NS NSZn2+ NS S S S S S NS NSAg+ NS NS NS NS S S NS NSPb2+ NS NS NS NS S NS NS NS Matter And Measurement
    • 160. Solution Chemistry• It is helpful to pay attention to exactly what species are present in a reaction mixture (i.e., solid, liquid, gas, aqueous solution).• If we are to understand reactivity, we must be aware of just what is changing during the course of a reaction. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 161. Molecular EquationThe molecular equation lists the reactantsand products in their molecular form.AgNO3 (aq) + KCl (aq) → AgCl (s) + KNO3 (aq) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 162. Ionic Equation• In the ionic equation all strong electrolytes (strong acids, strong bases, and soluble ionic salts) are dissociated into their ions.• This more accurately reflects the species that are found in the reaction mixture. Ag+ (aq) + NO3- (aq) + K+ (aq) + Cl- (aq) → AgCl (s) + K+ (aq) + NO3- (aq) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 163. Net Ionic Equation• To form the net ionic equation, cross out anything that does not change from the left side of the equation to the right. Ag+(aq) + NO3-(aq) + K+(aq) + Cl-(aq) → Matter AgCl (s) + K+(aq) + NO3-(aq) And Measurement © 2009, Prentice-Hall, Inc.
    • 164. Net Ionic Equation• To form the net ionic equation, cross out anything that does not change from the left side of the equation to the right.• The only things left in the equation are those things that change (i.e., react) during the course of the reaction. Ag+(aq) + Cl-(aq) → AgCl (s) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 165. Net Ionic Equation• To form the net ionic equation, cross out anything that does not change from the left side of the equation to the right.• The only things left in the equation are those things that change (i.e., react) during the course of the reaction.• Those things that didn’t change (and were deleted from the net ionic equation) are called spectator ions. Ag+(aq) + NO3-(aq) + K+(aq) + Cl-(aq) → Matter AgCl (s) + K+(aq) + NO3-(aq) And Measurement © 2009, Prentice-Hall, Inc.
    • 166. Writing Net Ionic Equations1. Write a balanced molecular equation.2. Dissociate all strong electrolytes.3. Cross out anything that remains unchanged from the left side to the right side of the equation.4. Write the net ionic equation with the species that remain. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 167. Acids • Arrhenius defined acids as substances that increase the concentration of H+ when dissolved in water. • Brønsted and Lowry defined them as proton donors. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 168. Acids There are only seven strong acids: • Hydrochloric (HCl) • Hydrobromic (HBr) • Hydroiodic (HI) • Nitric (HNO3) • Sulfuric (H2SO4) • Chloric (HClO3) • Perchloric (HClO4) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 169. Bases• Arrhenius defined bases as substances that increase the concentration of OH− when dissolved in water.• Brønsted and Lowry defined them as proton acceptors. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 170. BasesThe strong basesare the solublemetal salts ofhydroxide ion:• Alkali metals• Calcium• Strontium• Barium Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 171. Acid-Base Reactions In an acid-base reaction, the acid donates a proton (H+) to the base. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 172. Neutralization Reactions Generally, when solutions of an acid and a base are combined, the products are a salt and water.CH3COOH (aq) + NaOH (aq) →CH3COONa (aq) + H2O (l) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 173. Neutralization ReactionsWhen a strong acid reacts with a strong base, the netionic equation is… HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (l) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 174. Neutralization ReactionsWhen a strong acid reacts with a strong base, the netionic equation is… HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (l) H+ (aq) + Cl- (aq) + Na+ (aq) + OH-(aq) → Na+ (aq) + Cl- (aq) + H2O (l) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 175. Neutralization ReactionsWhen a strong acid reacts with a strong base, the netionic equation is… HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (l) H+ (aq) + Cl- (aq) + Na+ (aq) + OH-(aq) → Na+ (aq) + Cl- (aq) + H2O (l) H+ (aq) + OH- (aq) → H2O (l) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 176. Gas-Forming Reactions • Some metathesis reactions do not give the product expected. • In this reaction, the expected product (H2CO3) decomposes to give a gaseous product (CO2).CaCO3 (s) + HCl (aq) →CaCl2 (aq) + CO2 (g) + H2O (l) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 177. Gas-Forming Reactions When a carbonate or bicarbonate reacts with an acid, the products are a salt, carbon dioxide, and water. CaCO3 (s) + HCl (aq) →CaCl2 (aq) + CO2 (g) + H2O (l)NaHCO3 (aq) + HBr (aq) →NaBr (aq) + CO2 (g) + H2O (l) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 178. Gas-Forming Reactions Similarly, when a sulfite reacts with an acid, the products are a salt, sulfur dioxide, and water.SrSO3 (s) + 2 HI (aq) →SrI2 (aq) + SO2 (g) + H2O (l) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 179. Gas-Forming Reactions• This reaction gives the predicted product, but you had better carry it out in the hood, or you will be very unpopular!• But just as in the previous examples, a gas is formed as a product of this reaction.Na2S (aq) + H2SO4 (aq) → Na2SO4 (aq) + H2S (g) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 180. Oxidation-Reduction Reactions• An oxidation occurs when an atom or ion loses electrons.• A reduction occurs when an atom or ion gains electrons.• One cannot occur without the other. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 181. Oxidation NumbersTo determine if an oxidation-reductionreaction has occurred, we assign anoxidation number to each element in aneutral compound or charged entity. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 182. Oxidation Numbers• Elements in their elemental form have an oxidation number of 0.• The oxidation number of a monatomic ion is the same as its charge. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 183. Oxidation Numbers• Nonmetals tend to have negative oxidation numbers, although some are positive in certain compounds or ions. Oxygen has an oxidation number of −2, except in the peroxide ion in which it has an oxidation number of −1. Hydrogen is −1 when bonded to a metal, +1 when bonded to a nonmetal. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 184. Oxidation Numbers• Nonmetals tend to have negative oxidation numbers, although some are positive in certain compounds or ions. Fluorine always has an oxidation number of −1. The other halogens have an oxidation number of −1 when they are negative; they can have positive oxidation numbers, however, most notably in oxyanions. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 185. Oxidation Numbers• The sum of the oxidation numbers in a neutral compound is 0.• The sum of the oxidation numbers in a polyatomic ion is the charge on the ion. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 186. Displacement Reactions • In displacement reactions, ions oxidize an element. • The ions, then, are reduced. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 187. Displacement Reactions In this reaction, silver ions oxidize copper metal.Cu (s) + 2 Ag+ (aq) → Cu2+ (aq) + 2 Ag (s) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 188. Displacement Reactions The reverse reaction, however, does not occur. xCu2+ (aq) + 2 Ag (s) → Cu (s) + 2 Ag+ (aq) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 189. Activity Series Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 190. Molarity• Two solutions can contain the same compounds but be quite different because the proportions of those compounds are different.• Molarity is one way to measure the concentration of a solution. moles of solute Molarity (M) = volume of solution in liters Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 191. Mixing a Solution • To create a solution of a known molarity, one weighs out a known mass (and, therefore, number of moles) of the solute. • The solute is added to a volumetric flask, and solvent is added to the line on the neck of the flask. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 192. Dilution• One can also dilute a more concentrated solution by – Using a pipet to deliver a volume of the solution to a new volumetric flask, and – Adding solvent to the line on the neck of the new flask. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 193. DilutionThe molarity of the new solution can be determinedfrom the equation Mc × Vc = Md × Vd,where Mc and Md are the molarity of the concentrated and dilutesolutions, respectively, and Vc and Vd are the volumes of thetwo solutions. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 194. Using Molarities inStoichiometric Calculations Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 195. Titration Titration is an analytical technique in which one can calculate the concentration of a solute in a solution. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 196. Chemistry, The Central Science, 11th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten Chapter 5 Thermochemistry John D. Bookstaver MatterSt. Charles Community College And Cottleville, MO Measurement © 2009, Prentice-Hall, Inc.
    • 197. Energy• Energy is the ability to do work or transfer heat. – Energy used to cause an object that has mass to move is called work. – Energy used to cause the temperature of an object to rise is called heat. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 198. Potential EnergyPotential energy is energy an objectpossesses by virtue of its position or chemicalcomposition. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 199. Kinetic EnergyKinetic energy is energy an object possessesby virtue of its motion. 1 KE =  mv2 2 Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 200. Units of Energy• The SI unit of energy is the joule (J). kg m2 1 J = 1  s2• An older, non-SI unit is still in widespread use: the calorie (cal). 1 cal = 4.184 J Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 201. Definitions:System and Surroundings • The system includes the molecules we want to study (here, the hydrogen and oxygen molecules). • The surroundings are everything else (here, the cylinder and piston). Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 202. Definitions: Work• Energy used to move an object over some distance is work.• w=F×d where w is work, F is the force, and d is the distance over which the force is exerted. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 203. Heat • Energy can also be transferred as heat. • Heat flows from warmer objects to cooler objects. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 204. Conversion of Energy• Energy can be converted from one type to another.• For example, the cyclist above has potential energy as she sits on top of the hill. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 205. Conversion of Energy• As she coasts down the hill, her potential energy is converted to kinetic energy.• At the bottom, all the potential energy she had at the top of the hill is now kinetic energy. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 206. First Law of Thermodynamics• Energy is neither created nor destroyed.• In other words, the total energy of the universe is a constant; if the system loses energy, it must be gained by the surroundings, and vice versa. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 207. Internal EnergyThe internal energy of a system is the sum of allkinetic and potential energies of all componentsof the system; we call it E. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 208. Internal EnergyBy definition, the change in internal energy, ∆E,is the final energy of the system minus the initialenergy of the system: ∆E = Efinal − Einitial Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 209. Changes in Internal Energy • If ∆E > 0, Efinal > Einitial – Therefore, the system absorbed energy from the surroundings. – This energy change is called endergonic. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 210. Changes in Internal Energy • If ∆E < 0, Efinal < Einitial – Therefore, the system released energy to the surroundings. – This energy change is called exergonic. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 211. Changes in Internal Energy • When energy is exchanged between the system and the surroundings, it is exchanged as either heat (q) or work (w). • That is, ∆E = q + w. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 212. ∆E, q, w, and Their Signs Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 213. Exchange of Heat between System and Surroundings• When heat is absorbed by the system from the surroundings, the process is endothermic. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 214. Exchange of Heat between System and Surroundings• When heat is absorbed by the system from the surroundings, the process is endothermic.• When heat is released by the system into the surroundings, the process is exothermic. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 215. State FunctionsUsually we have no way of knowing theinternal energy of a system; finding that valueis simply too complex a problem. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 216. State Functions• However, we do know that the internal energy of a system is independent of the path by which the system achieved that state. – In the system below, the water could have reached room temperature from either direction. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 217. State Functions• Therefore, internal energy is a state function.• It depends only on the present state of the system, not on the path by which the system arrived at that state.• And so, ∆E depends only on Einitial and Efinal. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 218. State Functions • However, q and w are not state functions. • Whether the battery is shorted out or is discharged by running the fan, its ∆E is the same. – But q and w are different in the two cases. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 219. Work Usually in an open container the only work done is by a gas pushing on the surroundings (or by the surroundings pushing on the gas). Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 220. WorkWe can measure the work done by the gas ifthe reaction is done in a vessel that has beenfitted with a piston. w = -P∆V Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 221. Enthalpy• If a process takes place at constant pressure (as the majority of processes we study do) and the only work done is this pressure-volume work, we can account for heat flow during the process by measuring the enthalpy of the system.• Enthalpy is the internal energy plus the product of pressure and volume: H = E + PV Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 222. Enthalpy• When the system changes at constant pressure, the change in enthalpy, ∆H, is ∆H = ∆(E + PV)• This can be written ∆H = ∆E + P∆V Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 223. Enthalpy• Since ∆E = q + w and w = -P∆V, we can substitute these into the enthalpy expression: ∆H = ∆E + P∆V ∆H = (q+w) − w ∆H = q• So, at constant pressure, the change in enthalpy is the heat gained or lost. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 224. Endothermicity and Exothermicity • A process is endothermic when ∆H is positive. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 225. Endothermicity and Exothermicity • A process is endothermic when ∆H is positive. • A process is exothermic when ∆H is negative. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 226. Enthalpy of Reaction The change in enthalpy, ∆H, is the enthalpy of the products minus the enthalpy of the reactants:∆H = Hproducts − Hreactants Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 227. Enthalpy of ReactionThis quantity, ∆H, is called the enthalpy ofreaction, or the heat of reaction. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 228. The Truth about Enthalpy• Enthalpy is an extensive property.• ∆H for a reaction in the forward direction is equal in size, but opposite in sign, to ∆H for the reverse reaction.• ∆H for a reaction depends on the state of the products and the state of the reactants. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 229. Calorimetry Since we cannot know the exact enthalpy of the reactants and products, we measure ∆H through calorimetry, the measurement of heat flow. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 230. Heat Capacity and Specific Heat The amount of energy required to raise the temperature of a substance by 1 K (1°C) is its heat capacity. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 231. Heat Capacity and Specific Heat We define specific heat capacity (or simply specific heat) as the amount of energy required to raise the temperature of 1 g of a substance by 1 K. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 232. Heat Capacity and Specific HeatSpecific heat, then, is heat transferredSpecific heat = mass × temperature change q s= m × ∆T Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 233. Constant Pressure Calorimetry By carrying out a reaction in aqueous solution in a simple calorimeter such as this one, one can indirectly measure the heat change for the system by measuring the heat change for the water in the calorimeter. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 234. Constant Pressure Calorimetry Because the specific heat for water is well known (4.184 J/g-K), we can measure ∆H for the reaction with this equation: q = m × s × ∆T Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 235. Bomb Calorimetry• Reactions can be carried out in a sealed “bomb” such as this one.• The heat absorbed (or released) by the water is a very good approximation of the enthalpy change for the reaction. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 236. Bomb Calorimetry• Because the volume in the bomb calorimeter is constant, what is measured is really the change in internal energy, ∆E, not ∆H.• For most reactions, the difference is very small. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 237. Enthalpies of FormationEnthalpy of formation, ∆Hf, is ….the enthalpy change for the reaction inwhich a compound is made from itsconstituent elements in their elementalforms. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 238. Hesss LawIf a reaction is carried out in a series ofsteps, ∆Hfor the overall reaction = the sum of theenthalpy changes for individual steps. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 239. Standard Enthalpies of Formation Standard enthalpies of formation, ∆Hf°, are measured under standard conditions (25 °C and 1.00 atm pressure). (Text page 184) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 240. Calculation of ∆H C3H8 (g) + 5 O2 (g) → 3 CO2 (g) + 4 H2O (l) • Imagine this as occurring in three steps:C3H8 (g) → 3 C (graphite) + 4 H2 (g)3 C (graphite) + 3 O2 (g) → 3 CO2 (g)4 H2 (g) + 2 O2 (g) → 4 H2O (l) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 241. Calculation of ∆H C3H8 (g) + 5 O2 (g) → 3 CO2 (g) + 4 H2O (l) • Imagine this as occurring in three steps:C3H8 (g) → 3 C (graphite) + 4 H2 (g)3 C (graphite) + 3 O2 (g) → 3 CO2 (g)4 H2 (g) + 2 O2 (g) → 4 H2O (l) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 242. Calculation of ∆H C3H8 (g) + 5 O2 (g) → 3 CO2 (g) + 4 H2O (l) • Imagine this as occurring in three steps:C3H8 (g) → 3 C (graphite) + 4 H2 (g)3 C (graphite) + 3 O2 (g) → 3 CO2 (g)4 H2 (g) + 2 O2 (g) → 4 H2O (l) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 243. Calculation of ∆H C3H8 (g) + 5 O2 (g) → 3 CO2 (g) + 4 H2O (l) • The sum of these equations is:C3H8 (g) → 3 C (graphite) + 4 H2 (g)3 C (graphite) + 3 O2 (g) → 3 CO2 (g)4 H2 (g) + 2 O2 (g) → 4 H2O (l)C3H8 (g) + 5 O2 (g) → 3 CO2 (g) + 4 H2O (l) Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 244. Calculation of ∆HWe can use Hess’s law in this way:∆H = Σ n ∆Hf°products – Σ m ∆Hf° reactantswhere n and m are the stoichiometriccoefficients. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 245. Calculation of ∆H C3H8 (g) + 5 O2 (g) → 3 CO2 (g) + 4 H2O (l)∆H = [3(-393.5 kJ) + 4(-285.8 kJ)] – [1(-103.85 kJ) + 5(0 kJ)] = [(-1180.5 kJ) + (-1143.2 kJ)] – [(-103.85 kJ) + (0 kJ)] = (-2323.7 kJ) – (-103.85 kJ) = -2219.9 kJ ∆Hf of the most stable Form of any element Is 0 ...no formation Needed. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 246. Hess’s Law∀ ∆H is well known for many reactions, and it is inconvenient to measure ∆H for every reaction in which we are interested.• However, we can estimate ∆H using published ∆H values and the properties of enthalpy. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 247. Hess’s Law Hess’s law states that “[i]f a reaction is carried out in a series of steps, ∆H for the overall reaction will be equal to the sum of the enthalpy changes for the individual steps.” Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 248. Hess’s Law Because ∆H is a state function, the total enthalpy change depends only on the initial state of the reactants and the final state of the products. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 249. Energy in Foods Most of the fuel in the food we eat comes from carbohydrates and fats. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 250. Energy in FuelsThe vastmajority of theenergyconsumed inthis countrycomes fromfossil fuels. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 251. Chemistry, The Central Science, 11th editionTheodore L. Brown; H. Eugene LeMay, Jr.;and Bruce E. Bursten Chapter 6 Electronic Structure of Atoms Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 252. The Nature of Energy • Why an object can glow when its temperature increases? • The wave nature of light does not explain it Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 253. Waves • To understand the electronic structure of atoms, one must understand the nature of electromagnetic radiation. • The distance between corresponding points on adjacent waves is the wavelength (λ). Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 254. Waves • The number of waves passing a given point per unit of time is the frequency (ν). • For waves traveling at the same velocity, the longer the wavelength, the smaller the frequency. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 255. Electromagnetic Radiation• All electromagnetic radiation travels at the same velocity: the speed of light (c), 3.00 × 108 m/s.• Therefore,c = λν Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 256. Matter And Measurement© 2009, Prentice-Hall, Inc.
    • 257. The Nature of Energy Another mystery in the early 20th century involved the emission spectra observed from energy emitted by atoms and molecules. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 258. The Nature of Energy • For atoms and molecules one does not observe a continuous spectrum, as one gets from a white light source. • Only a line spectrum of discrete wavelengths is observed. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 259. The Nature of Energy • Max Planck explained it by assuming that energy comes in packets called quanta. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 260. The Nature of Energy• Einstein used this assumption to explain the photoelectric effect.• He concluded that energy is proportional to frequency:E = hν where h is Planck’s constant, 6.626 × 10−34 J-s. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 261. The Nature of Energy• Therefore, if one knows the wavelength of light, one can calculate the energy in one photon, or packet, of that light:c = λνE = hν Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 262. The Nature of Energy • Niels Bohr adopted Planck’s assumption and explained these phenomena in this way: 1. Electrons in an atom can only occupy certain orbits (corresponding to certain energies). Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 263. The Nature of Energy • Niels Bohr adopted Planck’s assumption and explained these phenomena in this way: 1. Electrons in permitted orbits have specific, “allowed” energies; these energies will not be radiated from the atom. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 264. The Nature of Energy • Niels Bohr adopted Planck’s assumption and explained these phenomena in this way: 1. Energy is only absorbed or emitted in such a way as to move an electron from one “allowed” energy state to another; the energy is defined by Matter E = hν And Measurement © 2009, Prentice-Hall, Inc.
    • 265. The Nature of Energy The energy absorbed or emitted from the process of electron promotion or demotion can be calculated by the equation: 1 1 ∆E = −hcRH ( nf 2 - 2 ni ) where RH is the Rydberg constant, and ni and nf are the initial and final energy levels of the electron. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 266. The Wave Nature of Matter • Louis de Broglie posited that if light can have material properties, matter should exhibit wave properties. • He demonstrated that the relationship between mass and wavelength was h λ = mv Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 267. The Uncertainty Principle • Heisenberg showed that the more precisely the momentum of a particle is known, the less precisely is its position known: h (∆x) (∆mv) ≥ 4π • In many cases, our uncertainty of the whereabouts of an electron is greater than the size of the atom itself! Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 268. Quantum Mechanics • Erwin Schrödinger developed a mathematical treatment into which both the wave and particle nature of matter could be incorporated. • It is known as quantum mechanics. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 269. Schrödinger equationTime dependent formTime independent form Matter And Measurement
    • 270. Quantum Mechanics• The wave equation is designated with a lower case Greek psi (ψ).• The square of the wave equation, ψ2, gives a probability density map of where an electron has a certain statistical likelihood of being at any given instant Matter in time. And Measurement © 2009, Prentice-Hall, Inc.
    • 271. Quantum Numbers • Solving the wave equation gives a set of wave functions, or orbitals, and their corresponding energies. • Each orbital describes a spatial distribution of electron density. • An orbital is described by a set of three quantum numbers. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 272. Principal Quantum Number (n) • The principal quantum number, n, describes the energy level on which the orbital resides. • The values of n are integers ≥ 1. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 273. Angular Momentum QuantumNumber (l) • This quantum number defines the shape of the orbital. • Allowed values of l are integers ranging from 0 to n − 1. • We use letter designations to communicate the different values of l and, therefore, the shapes and types of orbitals. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 274. Angular Momentum QuantumNumber (l) Value of l 0 1 2 3 Type of orbital s p d f Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 275. Magnetic Quantum Number (ml) • The magnetic quantum number describes the three-dimensional orientation of the orbital. • Allowed values of ml are integers ranging from -l to l: −l ≤ ml ≤ l. • Therefore, on any given energy level, there can be up to 1 s orbital, 3 p Matter orbitals, 5 d orbitals, 7 f orbitals, etc. And Measurement © 2009, Prentice-Hall, Inc.
    • 276. Magnetic Quantum Number (ml) • Orbitals with the same value of n form a shell. • Different orbital types within a shell are subshells. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 277. s Orbitals • The value of l for s orbitals is 0. • They are spherical in shape. • The radius of the sphere increases with the value of n. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 278. s Orbitals Observing a graph of probabilities of finding an electron versus distance from the nucleus, we see that s orbitals possess n−1 nodes, or regions where there is 0 probability of finding an electron. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 279. p Orbitals • The value of l for p orbitals is 1. • They have two lobes with a node between them. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 280. d Orbitals • The value of l for a d orbital is 2. • Four of the five d orbitals have 4 lobes; the other resembles a p orbital with a doughnut around the center. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 281. Energies of Orbitals • For a one-electron hydrogen atom, orbitals on the same energy level have the same energy. • That is, they are degenerate. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 282. Energies of Orbitals • As the number of electrons increases, though, so does the repulsion between them. • Therefore, in many- electron atoms, orbitals on the same energy level are no longer degenerate. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 283. Spin Quantum Number, ms• In the 1920s, it was discovered that two electrons in the same orbital do not have exactly the same energy.• The “spin” of an electron describes its magnetic field, which affects its energy. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 284. Spin Quantum Number, ms• This led to a fourth quantum number, the spin quantum number, ms.• The spin quantum number has only 2 allowed values: +1/2 and −1/2. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 285. Pauli Exclusion Principle• No two electrons in the same atom can have exactly the same energy.• Therefore, no two electrons in the same atom can have identical sets of quantum numbers. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 286. Electron Configurations • This shows the distribution of all electrons in an atom. • Each component consists of – A number denoting the energy level, Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 287. Electron Configurations • This shows the distribution of all electrons in an atom • Each component consists of – A number denoting the energy level, – A letter denoting the type of orbital, Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 288. Electron Configurations • This shows the distribution of all electrons in an atom. • Each component consists of – A number denoting the energy level, – A letter denoting the type of orbital, – A superscript denoting the number of electrons in those orbitals. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 289. First Klechkovsky’s RuleAs atomic number increases, filling of orbitals in the atomgoes from orbitals with the smaller sum of n and l (n+l) toorbitals with the larger sum of n and l (n+l). Matter And Measurement
    • 290. Orbital Diagrams • Each box in the diagram represents one orbital. • Half-arrows represent the electrons. • The direction of the arrow represents the relative spin of the electron. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 291. Hund’s Rule “For degenerate orbitals, the lowest energy is attained when the number of electrons with the same spin is maximized.” Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 292. Periodic Table • We fill orbitals in increasing order of energy. • Different blocks on the periodic table (shaded in different colors in this chart) correspond to different types of orbitals. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 293. Some Anomalies For instance, the electron configuration for copper is [Ar] 4s1 3d5 rather than the expected [Ar] 4s2 3d4. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 294. Second Klechkovsky’s RuleWhen the sum of n and l (n+l) is identical, the filling oforbitals goes in the direction of rising of the main quantumnumber (n).Exceptions: Cr, Cu, Nb, Mo, Ru, Rh, Pd, Ag, Pt, Au Matter And Measurement
    • 295. Some Anomalies Some irregularities occur when there are enough electrons to half- fill s and d orbitals on a given row. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 296. Some Anomalies • This occurs because the 4s and 3d orbitals are very close in energy. • These anomalies occur in f-block atoms, as well. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 297. Chemistry, The Central Science, 11th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten Chapter 7 Periodic Properties of the Elements John D. Bookstaver MatterSt. Charles Community College And Measurement Cottleville, MO © 2009, Prentice-Hall,
    • 298. Development of Periodic Table• Elements in the same group generally have similar chemical properties.• Physical properties are not necessarily similar, however. Matter And Measurement © 2009, Prentice-Hall,
    • 299. Development of Periodic Table Dmitri Mendeleev and Lothar Meyer independently came to the same conclusion about how elements should be grouped. Matter And Measurement © 2009, Prentice-Hall,
    • 300. Development of Periodic TableMendeleev, for instance, predicted thediscovery of germanium (which he called eka-silicon) as an element with an atomic weightbetween that of zinc and arsenic, but with Matter Andchemical properties similar to those of silicon. Measurement © 2009, Prentice-Hall,
    • 301. Periodic Trends• In this chapter, we will rationalize observed trends in – Sizes of atoms and ions. – Ionization energy. – Electron affinity. Matter And Measurement © 2009, Prentice-Hall,
    • 302. Effective Nuclear Charge • In a many-electron atom, electrons are both attracted to the nucleus and repelled by other electrons. • The nuclear charge that an electron experiences depends on both factors. Matter And Measurement © 2009, Prentice-Hall,
    • 303. Effective Nuclear Charge The effective nuclear charge, Zeff, is found this way: Zeff = Z − S where Z is the atomic number and S is a screening constant, usually close to the number of inner Matter And electrons. Measurement © 2009, Prentice-Hall,
    • 304. Other Electrons in group(s) with Electrons in all group(s) with electrons in Group principal quantum number principal quantum number the same n-1 < n-1 group [1s] 0.3 N/A N/A [ns,np] 0.35 0.85 1[nd] or [nf] 0.35 1 1 Matter And Measurement © 2009, Prentice-Hall,
    • 305. What Is the Size of an Atom?The bonding atomicradius is defined asone-half of thedistance betweencovalently bondednuclei. Matter And Measurement © 2009, Prentice-Hall,
    • 306. Sizes of Atoms Bonding atomic radius tends to… …decrease from left to right across a row (due to increasing Zeff). …increase from top to bottom of a column (due to increasing value of n). Matter And Measurement © 2009, Prentice-Hall,
    • 307. Sizes of Ions • Ionic size depends upon: – The nuclear charge. – The number of electrons. – The orbitals in which electrons reside. Matter And Measurement © 2009, Prentice-Hall,
    • 308. Sizes of Ions • Cations are smaller than their parent atoms. – The outermost electron is removed and repulsions between electrons are reduced. Matter And Measurement © 2009, Prentice-Hall,
    • 309. Sizes of Ions • Anions are larger than their parent atoms. – Electrons are added and repulsions between electrons are increased. Matter And Measurement © 2009, Prentice-Hall,
    • 310. Sizes of Ions• Ions increase in size as you go down a column. – This is due to increasing value of n. Matter And Measurement © 2009, Prentice-Hall,
    • 311. Sizes of Ions• In an isoelectronic series, ions have the same number of electrons.• Ionic size decreases with an increasing nuclear charge. Matter And Measurement © 2009, Prentice-Hall,
    • 312. Ionization Energy• The ionization energy is the amount of energy required to remove an electron from the ground state of a gaseous atom or ion. – The first ionization energy is that energy required to remove first electron. – The second ionization energy is that energy required to remove second electron, etc. Matter And Measurement © 2009, Prentice-Hall,
    • 313. Ionization Energy• It requires more energy to remove each successive electron.• When all valence electrons have been removed, the ionization energy takes a quantum leap. Matter And Measurement © 2009, Prentice-Hall,
    • 314. Trends in First Ionization Energies • As one goes down a column, less energy is required to remove the first electron. – For atoms in the same group, Zeff is essentially the same, but the valence electrons are farther from the nucleus. Matter And Measurement © 2009, Prentice-Hall,
    • 315. Trends in First Ionization Energies• Generally, as one goes across a row, it gets harder to remove an electron. – As you go from left to right, Zeff increases. Matter And Measurement © 2009, Prentice-Hall,
    • 316. Trends in First Ionization EnergiesHowever, there aretwo apparentdiscontinuities in thistrend. Matter And Measurement © 2009, Prentice-Hall,
    • 317. Trends in First Ionization Energies• The first occurs between Groups IIA and IIIA.• In this case the electron is removed from a p-orbital rather than an s-orbital. – The electron removed is farther from nucleus. – There is also a small amount of repulsion by Matter the s electrons. And Measurement © 2009, Prentice-Hall,
    • 318. Trends in First Ionization Energies• The second occurs between Groups VA and VIA. – The electron removed comes from doubly occupied orbital. – Repulsion from the other electron in the orbital aids in its removal. Matter And Measurement © 2009, Prentice-Hall,
    • 319. Electron AffinityElectron affinity is the energy changeaccompanying the addition of anelectron to a gaseous atom: Cl + e− → Cl− Matter And Measurement © 2009, Prentice-Hall,
    • 320. Trends in Electron Affinity In general, electron affinity becomes more exothermic as you go from left to right across a row. Matter And Measurement © 2009, Prentice-Hall,
    • 321. Trends in Electron Affinity There are again, however, two discontinuities in this trend. Matter And Measurement © 2009, Prentice-Hall,
    • 322. Trends in Electron Affinity • The first occurs between Groups IA and IIA. – The added electron must go in a p-orbital, not an s-orbital. – The electron is farther from nucleus and feels repulsion from the s-electrons. Matter And Measurement © 2009, Prentice-Hall,
    • 323. Trends in Electron Affinity • The second occurs between Groups IVA and VA. – Group VA has no empty orbitals. – The extra electron must go into an already occupied orbital, creating repulsion. Matter And Measurement © 2009, Prentice-Hall,
    • 324. Properties of Metal, Nonmetals, and Metalloids Matter And Measurement © 2009, Prentice-Hall,
    • 325. Metals versus NonmetalsDifferences between metals and nonmetalstend to revolve around these properties. Matter And Measurement © 2009, Prentice-Hall,
    • 326. Metals versus Nonmetals• Metals tend to form cations.• Nonmetals tend to form anions. Matter And Measurement © 2009, Prentice-Hall,
    • 327. Metals They tend to be lustrous, malleable, ductile, and good conductors of heat and electricity. Matter And Measurement © 2009, Prentice-Hall,
    • 328. Metals• Compounds formed between metals and nonmetals tend to be ionic.• Metal oxides tend to be basic. Matter And Measurement © 2009, Prentice-Hall,
    • 329. Nonmetals • These are dull, brittle substances that are poor conductors of heat and electricity. • They tend to gain electrons in reactions with metals to acquire a noble gas configuration. Matter And Measurement © 2009, Prentice-Hall,
    • 330. Nonmetals• Substances containing only nonmetals are molecular compounds.• Most nonmetal oxides are acidic. Matter And Measurement © 2009, Prentice-Hall,
    • 331. Metalloids • These have some characteristics of metals and some of nonmetals. • For instance, silicon looks shiny, but is brittle and fairly poor conductor. Matter And Measurement © 2009, Prentice-Hall,
    • 332. Group Trends Matter And Measurement © 2009, Prentice-Hall,
    • 333. Alkali Metals• Alkali metals are soft, metallic solids.• The name comes from the Arabic word for ashes. Matter And Measurement © 2009, Prentice-Hall,
    • 334. Alkali Metals• They are found only in compounds in nature, not in their elemental forms.• They have low densities and melting points.• They also have low ionization energies. Matter And Measurement © 2009, Prentice-Hall,
    • 335. Alkali MetalsTheir reactions with water are famously exothermic. Matter And Measurement © 2009, Prentice-Hall,
    • 336. Alkali Metals• Alkali metals (except Li) react with oxygen to form peroxides.• K, Rb, and Cs also form superoxides: K + O2 → KO2• They produce bright colors when placed in a flame. Matter And Measurement © 2009, Prentice-Hall,
    • 337. Alkaline Earth Metals• Alkaline earth metals have higher densities and melting points than alkali metals.• Their ionization energies are low, but not as low as those of alkali metals. Matter And Measurement © 2009, Prentice-Hall,
    • 338. Alkaline Earth Metals• Beryllium does not react with water and magnesium reacts only with steam, but the others react readily with water.• Reactivity tends to increase as you go down the group. Matter And Measurement © 2009, Prentice-Hall,
    • 339. Group 6A• Oxygen, sulfur, and selenium are nonmetals.• Tellurium is a metalloid.• The radioactive polonium is a metal. Matter And Measurement © 2009, Prentice-Hall,
    • 340. Oxygen • There are two allotropes of oxygen: – O2 – O3, ozone • There can be three anions: – O2−, oxide – O22−, peroxide – O21−, superoxide • It tends to take electrons from other elements (oxidation). Matter And Measurement © 2009, Prentice-Hall,
    • 341. Sulfur• Sulfur is a weaker oxidizer than oxygen.• The most stable allotrope is S8, a ringed molecule. Matter And Measurement © 2009, Prentice-Hall,
    • 342. Group VIIA: Halogens• The halogens are prototypical nonmetals.• The name comes from the Greek words halos and gennao: “salt formers”. Matter And Measurement © 2009, Prentice-Hall,
    • 343. Group VIIA: Halogens • They have large, negative electron affinities. – Therefore, they tend to oxidize other elements easily. • They react directly with metals to form metal halides. • Chlorine is added to water supplies to serve as a disinfectant Matter And Measurement © 2009, Prentice-Hall,
    • 344. Group VIIIA: Noble Gases• The noble gases have astronomical ionization energies.• Their electron affinities are positive. – Therefore, they are relatively unreactive. Matter• They are found as monatomic gases. And Measurement © 2009, Prentice-Hall,
    • 345. Group VIIIA: Noble Gases• Xe forms three compounds: – XeF2 – XeF4 (at right) – XeF6• Kr forms only one stable compound: – KrF2• The unstable HArF was Matter And synthesized in 2000. Measurement © 2009, Prentice-Hall,
    • 346. Chemistry, The Central Science, 11th edition Theodore L. Brown, H. Eugene LeMay, Jr., and Bruce E. Bursten Chapter 8 Concepts of Chemical Bonding John D. Bookstaver MatterSt. Charles Community College And Measurement Cottleville, MO © 2009, Prentice-Hall,
    • 347. Chemical Bonds • Three basic types of bonds – Ionic • Electrostatic attraction between ions – Covalent • Sharing of electrons – Metallic • Metal atoms bonded to several other atoms • Lewis Symbols Matter • Octet Rule And Measurement © 2009, Prentice-Hall,
    • 348. Ionic Bonding Matter And Measurement © 2009, Prentice-Hall,
    • 349. Energetics of Ionic Bonding As we saw in the last chapter, it takes 495 kJ/mol to remove electrons from sodium. Matter And Measurement © 2009, Prentice-Hall,
    • 350. Energetics of Ionic BondingWe get 349 kJ/molback by givingelectrons tochlorine. Matter And Measurement © 2009, Prentice-Hall,
    • 351. Energetics of Ionic Bonding But these numbers don’t explain why the reaction of sodium metal and chlorine gas to form sodium chloride is so exothermic! Matter And Measurement © 2009, Prentice-Hall,
    • 352. Energetics of Ionic Bonding• There must be a third piece to the puzzle.• What is as yet unaccounted for is the electrostatic attraction between the newly-formed sodium cation and chloride anion. Matter And Measurement © 2009, Prentice-Hall,
    • 353. Lattice Energy• This third piece of the puzzle is the lattice energy: – The energy required to completely separate a mole of a solid ionic compound into its gaseous ions.• The energy associated with electrostatic interactions is governed by Coulomb’s law: Q 1Q 2 Eel = κ d Matter And Measurement © 2009, Prentice-Hall,
    • 354. Lattice Energy• Lattice energy, then, increases with the charge on the ions.• It also increases with decreasing size of ions. Matter And Measurement © 2009, Prentice-Hall,
    • 355. Energetics of Ionic Bonding: Born-Haber cycle By accounting for all three energies (ionization energy, electron affinity, and lattice energy), we can get a good idea of the energetics involved in such a process. Matter And Measurement © 2009, Prentice-Hall,
    • 356. Energetics of Ionic Bonding• These phenomena also helps explain the “octet rule.”• Metals, for instance, tend to stop losing electrons once they attain a noble gas configuration because energy would be expended that cannot be overcome by lattice energies. Matter And Measurement © 2009, Prentice-Hall,
    • 357. Covalent Bonding • In covalent bonds atoms share electrons. • There are several electrostatic interactions in these bonds: – Attractions between electrons and nuclei – Repulsions between electrons – Repulsions between nuclei Matter And Measurement © 2009, Prentice-Hall,
    • 358. Polar Covalent Bonds • Though atoms often form compounds by sharing electrons, the electrons are not always shared equally.• Fluorine pulls harder on the electrons it shares with hydrogen than hydrogen does.• Therefore, the fluorine end of the molecule has more electron density than the hydrogen Matter And end. Measurement © 2009, Prentice-Hall,
    • 359. Electronegativity• Electronegativity is the ability of atoms in a molecule to attract electrons to themselves.• On the periodic chart, electronegativity increases as you go… – …from left to right across a row. – …from the bottom to the top of a column. Matter And Measurement © 2009, Prentice-Hall,
    • 360. Polar Covalent Bonds• When two atoms share electrons unequally, a bond dipole results.• The dipole moment, µ, produced by two equal but opposite charges separated by a distance, r, is calculated: µ = Qr• It is measured in debyes (D). Matter And Measurement © 2009, Prentice-Hall,
    • 361. Polar Covalent Bonds The greater the difference in electronegativity, the more polar is the bond. Matter And Measurement © 2009, Prentice-Hall,
    • 362. Lewis StructuresLewis structures are representations ofmolecules showing all electrons, bonding andnonbonding. Matter And Measurement © 2009, Prentice-Hall,
    • 363. Writing Lewis Structures 1. Find the sum of PCl3 valence electrons of all atoms in the polyatomic ion or molecule. – If it is an anion, add one electron for each5 + 3(7) = 26 negative charge. – If it is a cation, subtract one electron for each positive charge. Matter And Measurement © 2009, Prentice-Hall,
    • 364. Writing Lewis Structures • The central atom is the least electronegative element that isn’t hydrogen. Connect the outer atoms to it by single bonds.Keep track of the electrons: Matter26 - 6 = 20 And Measurement © 2009, Prentice-Hall,
    • 365. Writing Lewis Structures 1. Fill the octets of the outer atoms.Keep track of the electrons: Matter26 - 6 = 20; 20 - 18 = 2 And Measurement © 2009, Prentice-Hall,
    • 366. Writing Lewis Structures 1. Fill the octet of the central atom.Keep track of the electrons: Matter26 - 6 = 20; 20 - 18 = 2; 2 - 2 = 0 And Measurement © 2009, Prentice-Hall,
    • 367. Writing Lewis Structures 1. If you run out of electrons before the central atom has an octet… …form multiple bonds until it does. Matter And Measurement © 2009, Prentice-Hall,
    • 368. Writing Lewis Structures• Then assign formal charges. – For each atom, count the electrons in lone pairs and half the electrons it shares with other atoms. – Subtract that from the number of valence electrons for that atom: the difference is its formal charge. Matter And Measurement © 2009, Prentice-Hall,
    • 369. Writing Lewis Structures• The best Lewis structure… – …is the one with the fewest charges. – …puts a negative charge on the most electronegative atom. Matter And Measurement © 2009, Prentice-Hall,
    • 370. ResonanceThis is the Lewis +structure wewould draw forozone, O3. - Matter And Measurement © 2009, Prentice-Hall,
    • 371. Resonance • But this is at odds with the true, observed structure of ozone, in which… – …both O-O bonds are the same length. – …both outer oxygens have a charge of -1/2. Matter And Measurement © 2009, Prentice-Hall,
    • 372. Resonance• One Lewis structure cannot accurately depict a molecule like ozone.• We use multiple structures, resonance structures, to describe the molecule. Matter And Measurement © 2009, Prentice-Hall,
    • 373. Resonance Just as green is a synthesis of blue and yellow… …ozone is a synthesis of these two resonance structures. Matter And Measurement © 2009, Prentice-Hall,
    • 374. Resonance• In truth, the electrons that form the second C-O bond in the double bonds below do not always sit between that C and that O, but rather can move among the two oxygens and the carbon.• They are not localized; they are delocalized. Matter And Measurement © 2009, Prentice-Hall,
    • 375. Resonance • The organic compound benzene, C6H6, has two resonance structures. • It is commonly depicted as a hexagon with a circle inside to signify the delocalized electrons in the ring. Matter And Measurement © 2009, Prentice-Hall,
    • 376. Exceptions to the Octet Rule• There are three types of ions or molecules that do not follow the octet rule: – Ions or molecules with an odd number of electrons – Ions or molecules with less than an octet – Ions or molecules with more than eight valence electrons (an expanded octet) Matter And Measurement © 2009, Prentice-Hall,
    • 377. Odd Number of ElectronsThough relatively rare and usually quiteunstable and reactive, there are ions andmolecules with an odd number of electrons. Matter And Measurement © 2009, Prentice-Hall,
    • 378. Fewer Than Eight Electrons• Consider BF3: – Giving boron a filled octet places a negative charge on the boron and a positive charge on fluorine. – This would not be an accurate picture of the Matter distribution of electrons in BF3. And Measurement © 2009, Prentice-Hall,
    • 379. Fewer Than Eight ElectronsTherefore, structures that put a double bondbetween boron and fluorine are much lessimportant than the one that leaves boron withonly 6 valence electrons. Matter And Measurement © 2009, Prentice-Hall,
    • 380. Fewer Than Eight ElectronsThe lesson is: if filling the octet of the centralatom results in a negative charge on thecentral atom and a positive charge on themore electronegative outer atom, don’t fill theoctet of the central atom. Matter And Measurement © 2009, Prentice-Hall,
    • 381. More Than Eight Electrons • The only way PCl5 can exist is if phosphorus has 10 electrons around it. • It is allowed to expand the octet of atoms on the 3rd row or below. – Presumably d orbitals in these atoms participate in bonding. Matter And Measurement © 2009, Prentice-Hall,
    • 382. More Than Eight ElectronsEven though we can draw a Lewis structure for thephosphate ion that has only 8 electrons around thecentral phosphorus, the better structure puts adouble bond between the phosphorus and one ofthe oxygens. Matter And Measurement © 2009, Prentice-Hall,
    • 383. More Than Eight Electrons• This eliminates the charge on the phosphorus and the charge on one of the oxygens.• The lesson is: when the central atom in on the 3rd row or below and expanding its octet eliminates some formal charges, do so. Matter And Measurement © 2009, Prentice-Hall,
    • 384. Covalent Bond Strength• Most simply, the strength of a bond is measured by determining how much energy is required to break the bond.• This is the bond enthalpy.• The bond enthalpy for a Cl-Cl bond, D(Cl-Cl), is measured to be 242 kJ/mol. Matter And Measurement © 2009, Prentice-Hall,
    • 385. Average Bond Enthalpies• This table lists the average bond enthalpies for many different types of bonds.• Average bond enthalpies are positive, because bond breaking is an endothermic process. Matter And Measurement © 2009, Prentice-Hall,
    • 386. Average Bond EnthalpiesNOTE: These are average bond enthalpies, not absolute bond enthalpies; the C-H bonds in methane, CH4, will be a bit different than the C-H bond in chloroform, CHCl3. Matter And Measurement © 2009, Prentice-Hall,
    • 387. Enthalpies of Reaction• Yet another way to estimate ∆H for a reaction is to compare the bond enthalpies of bonds broken to the bond enthalpies of the new bonds formed.• In other words,∆Hrxn = Σ(bond enthalpies of bonds broken) - Matter And Σ(bond enthalpies of bonds formed) Measurement © 2009, Prentice-Hall,
    • 388. Enthalpies of ReactionCH4 (g) + Cl2 (g) → CH3Cl (g) + HCl (g)In this example, one C-H bond and one Cl-Cl bond are broken; one C-Cl and one H-Cl bond are formed. Matter And Measurement © 2009, Prentice-Hall,
    • 389. Enthalpies of ReactionSo,∆H = [D(C-H) + D(Cl-Cl)] - [D(C-Cl) + D(H-Cl)] = [(413 kJ) + (242 kJ)] - [(328 kJ) + (431 kJ)] = (655 kJ) - (759 kJ) = -104 kJ Matter And Measurement © 2009, Prentice-Hall,
    • 390. Bond Enthalpy and Bond Length• We can also measure an average bond length for different bond types.• As the number of bonds between two atoms increases, the bond length decreases. Matter And Measurement © 2009, Prentice-Hall,
    • 391. Chemistry, The Central Science, 11th edition Theodore L. Brown, H. Eugene LeMay, Jr., and Bruce E. Bursten Chapter 9 Molecular Geometries and Bonding Theories John D. Bookstaver MatterSt. Charles Community College And Measurement Cottleville, MO © 2009, Prentice-Hall,
    • 392. Molecular Shapes • The shape of a molecule plays an important role in its reactivity. • By noting the number of bonding and nonbonding electron pairs we can easily predict the shape of the molecule. Matter And Measurement © 2009, Prentice-Hall,
    • 393. What Determines the Shape of a Molecule?• Simply put, electron pairs, whether they be bonding or nonbonding, repel each other.• By assuming the electron pairs are placed as far as possible from each other, we can predict the shape of the molecule. Matter And Measurement © 2009, Prentice-Hall,
    • 394. Electron Domains • We can refer to the electron pairs as electron domains. • In a double or triple bond, all electrons shared between those two atoms are on the same side of the central atom;• The central atom in therefore, they count as this molecule, A, one electron domain. has four electron Matter domains. And Measurement © 2009, Prentice-Hall,
    • 395. Valence Shell Electron Pair Repulsion Theory (VSEPR)“The bestarrangement of agiven number ofelectron domains isthe one thatminimizes therepulsions amongthem.” Matter And Measurement © 2009, Prentice-Hall,
    • 396. Electron-Domain Geometries These are the electron-domain geometries for two through six electron domains around a central atom. Matter And Measurement © 2009, Prentice-Hall,
    • 397. Electron-Domain Geometries• All one must do is count the number of electron domains in the Lewis structure.• The geometry will be that which corresponds to the number of electron domains. Matter And Measurement © 2009, Prentice-Hall,
    • 398. Molecular Geometries• The electron-domain geometry is often not the shape of the molecule, however.• The molecular geometry is that defined by the positions of only the atoms in the molecules, not the nonbonding pairs. Matter And Measurement © 2009, Prentice-Hall,
    • 399. Molecular GeometriesWithin each electrondomain, then, theremight be more thanone moleculargeometry. Matter And Measurement © 2009, Prentice-Hall,
    • 400. Linear Electron Domain• In the linear domain, there is only one molecular geometry: linear.• NOTE: If there are only two atoms in the molecule, the molecule will be linear no Matter matter what the electron domain is. And Measurement © 2009, Prentice-Hall,
    • 401. Trigonal Planar Electron Domain• There are two molecular geometries: – Trigonal planar, if all the electron domains are bonding, – Bent, if one of the domains is a nonbonding pair. Matter And Measurement © 2009, Prentice-Hall,
    • 402. Nonbonding Pairs and Bond Angle• Nonbonding pairs are physically larger than bonding pairs.• Therefore, their repulsions are greater; this tends to decrease bond angles in a molecule. Matter And Measurement © 2009, Prentice-Hall,
    • 403. Multiple Bonds and Bond Angles • Double and triple bonds place greater electron density on one side of the central atom than do single bonds. • Therefore, they also affect bond angles. Matter And Measurement © 2009, Prentice-Hall,
    • 404. Tetrahedral Electron Domain• There are three molecular geometries: – Tetrahedral, if all are bonding pairs, – Trigonal pyramidal if one is a nonbonding pair, Matter – Bent if there are two nonbonding pairs. And Measurement © 2009, Prentice-Hall,
    • 405. Trigonal Bipyramidal Electron Domain • There are two distinct positions in this geometry: – Axial – Equatorial Matter And Measurement © 2009, Prentice-Hall,
    • 406. Trigonal Bipyramidal Electron DomainLower-energy conformations result fromhaving nonbonding electron pairs inequatorial, rather than axial, positions in thisgeometry. Matter And Measurement © 2009, Prentice-Hall,
    • 407. Trigonal Bipyramidal Electron Domain• There are four distinct molecular geometries in this domain: – Trigonal bipyramidal – Seesaw – T-shaped – Linear Matter And Measurement © 2009, Prentice-Hall,
    • 408. Octahedral Electron Domain • All positions are equivalent in the octahedral domain. • There are three molecular geometries: – Octahedral – Square pyramidal – Square planar Matter And Measurement © 2009, Prentice-Hall,
    • 409. Larger MoleculesIn larger molecules,it makes moresense to talk aboutthe geometry abouta particular atomrather than thegeometry of themolecule as awhole. Matter And Measurement © 2009, Prentice-Hall,
    • 410. Larger Molecules This approach makes sense, especially because larger molecules tend to react at a particular site in the molecule. Matter And Measurement © 2009, Prentice-Hall,
    • 411. Polarity• In Chapter 8 we discussed bond dipoles.• But just because a molecule possesses polar bonds does not mean the molecule as a whole will be polar. Matter And Measurement © 2009, Prentice-Hall,
    • 412. Polarity By adding the individual bond dipoles, one can determine the overall dipole moment for the molecule. Matter And Measurement © 2009, Prentice-Hall,
    • 413. Polarity Matter And Measurement © 2009, Prentice-Hall,
    • 414. Overlap and Bonding• We think of covalent bonds forming through the sharing of electrons by adjacent atoms.• In such an approach this can only occur when orbitals on the two atoms overlap. Matter And Measurement © 2009, Prentice-Hall,
    • 415. Overlap and Bonding• Increased overlap brings the electrons and nuclei closer together while simultaneously decreasing electron- electron repulsion.• However, if atoms get too close, the internuclear repulsion greatly raises the energy. Matter And Measurement © 2009, Prentice-Hall,
    • 416. Hybrid OrbitalsBut it’s hard to imagine tetrahedral, trigonalbipyramidal, and other geometries arisingfrom the atomic orbitals we recognize. Matter And Measurement © 2009, Prentice-Hall,
    • 417. Hybrid Orbitals• Consider beryllium: – In its ground electronic state, it would not be able to form bonds because it has no singly-occupied orbitals. Matter And Measurement © 2009, Prentice-Hall,
    • 418. Hybrid OrbitalsBut if it absorbs thesmall amount ofenergy needed topromote an electronfrom the 2s to the 2porbital, it can form twobonds. Matter And Measurement © 2009, Prentice-Hall,
    • 419. Hybrid Orbitals• Mixing the s and p orbitals yields two degenerate orbitals that are hybrids of the two orbitals. – These sp hybrid orbitals have two lobes like a p orbital. – One of the lobes is larger and more rounded as is the s orbital. Matter And Measurement © 2009, Prentice-Hall,
    • 420. Hybrid Orbitals• These two degenerate orbitals would align themselves 180° from each other.• This is consistent with the observed geometry of beryllium compounds: linear. Matter And Measurement © 2009, Prentice-Hall,
    • 421. Hybrid Orbitals• With hybrid orbitals the orbital diagram for beryllium would look like this.• The sp orbitals are higher in energy than the 1s orbital but lower than the 2p. Matter And Measurement © 2009, Prentice-Hall,
    • 422. Hybrid OrbitalsUsing a similar model for boron leads to… Matter And Measurement © 2009, Prentice-Hall,
    • 423. Hybrid Orbitals…three degenerate sp2 orbitals. Matter And Measurement © 2009, Prentice-Hall,
    • 424. Hybrid OrbitalsWith carbon we get… Matter And Measurement © 2009, Prentice-Hall,
    • 425. Hybrid Orbitals…four degenerate sp3 orbitals. Matter And Measurement © 2009, Prentice-Hall,
    • 426. Hybrid OrbitalsFor geometries involving expanded octets onthe central atom, we must use d orbitals inour hybrids. Matter And Measurement © 2009, Prentice-Hall,
    • 427. Hybrid Orbitals This leads to five degenerate sp3d orbitals… …or six degenerate sp3d2 orbitals. Matter And Measurement © 2009, Prentice-Hall,
    • 428. Hybrid OrbitalsOnce you know theelectron-domaingeometry, you knowthe hybridizationstate of the atom. Matter And Measurement © 2009, Prentice-Hall,
    • 429. Valence Bond Theory• Hybridization is a major player in this approach to bonding.• There are two ways orbitals can overlap to form bonds between atoms. Matter And Measurement © 2009, Prentice-Hall,
    • 430. Sigma (σ) Bonds• Sigma bonds are characterized by – Head-to-head overlap. – Cylindrical symmetry of electron density about the internuclear axis. Matter And Measurement © 2009, Prentice-Hall,
    • 431. Pi (π) Bonds• Pi bonds are characterized by – Side-to-side overlap. – Electron density above and below the internuclear axis. Matter And Measurement © 2009, Prentice-Hall,
    • 432. Single BondsSingle bonds are always σ bonds, because σoverlap is greater, resulting in a stronger bondand more energy lowering. Matter And Measurement © 2009, Prentice-Hall,
    • 433. Multiple BondsIn a multiple bond one of the bonds is a σ bondand the rest are π bonds. Matter And Measurement © 2009, Prentice-Hall,
    • 434. Multiple Bonds • In a molecule like formaldehyde (shown at left) an sp2 orbital on carbon overlaps in σ fashion with the corresponding orbital on the oxygen. • The unhybridized p orbitals overlap in π fashion. Matter And Measurement © 2009, Prentice-Hall,
    • 435. Multiple BondsIn triple bonds, as inacetylene, two sporbitals form a σbond between thecarbons, and twopairs of p orbitalsoverlap in π fashionto form the two πbonds. Matter And Measurement © 2009, Prentice-Hall,
    • 436. Delocalized Electrons: ResonanceWhen writing Lewis structures for species likethe nitrate ion, we draw resonance structures tomore accurately reflect the structure of themolecule or ion. Matter And Measurement © 2009, Prentice-Hall,
    • 437. Delocalized Electrons: Resonance • In reality, each of the four atoms in the nitrate ion has a p orbital. • The p orbitals on all three oxygens overlap with the p orbital on the central nitrogen. Matter And Measurement © 2009, Prentice-Hall,
    • 438. Delocalized Electrons: Resonance This means the π electrons are not localized between the nitrogen and one of the oxygens, but rather are delocalized throughout the ion. Matter And Measurement © 2009, Prentice-Hall,
    • 439. ResonanceThe organic moleculebenzene has six σbonds and a p orbitalon each carbon atom. Matter And Measurement © 2009, Prentice-Hall,
    • 440. Resonance• In reality the π electrons in benzene are not localized, but delocalized.• The even distribution of the π electrons in benzene makes the molecule unusually stable. Matter And Measurement © 2009, Prentice-Hall,
    • 441. Molecular Orbital (MO) TheoryThough valence bondtheory effectively conveysmost observed propertiesof ions and molecules,there are some conceptsbetter represented bymolecular orbitals. Matter And Measurement © 2009, Prentice-Hall,
    • 442. Molecular Orbital (MO) Theory• In MO theory, we invoke the wave nature of electrons.• If waves interact constructively, the resulting orbital is lower in energy: a bonding molecular orbital. Matter And Measurement © 2009, Prentice-Hall,
    • 443. Molecular Orbital (MO) TheoryIf waves interactdestructively, theresulting orbital ishigher in energy: anantibonding molecularorbital. Matter And Measurement © 2009, Prentice-Hall,
    • 444. MO Theory • In H2 the two electrons go into the bonding molecular orbital. • The bond order is one half the difference between the number of bonding and antibonding electrons. Matter And Measurement © 2009, Prentice-Hall,
    • 445. MO Theory For hydrogen, with two electrons in the bonding MO and none in the antibonding MO, the bond order is 1 (2 - 0) = 1 2 Matter And Measurement © 2009, Prentice-Hall,
    • 446. MO Theory• In the case of He2, the bond order would be 1 (2 - 2) = 0 2• Therefore, He2 does not exist. Matter And Measurement © 2009, Prentice-Hall,
    • 447. MO Theory • For atoms with both s and p orbitals, there are two types of interactions: – The s and the p orbitals that face each other overlap in σ fashion. – The other two sets of p orbitals overlap in π fashion. Matter And Measurement © 2009, Prentice-Hall,
    • 448. MO Theory• The resulting MO diagram looks like this.• There are both σ and π bonding molecular orbitals and σ* and π* antibonding molecular orbitals. Matter And Measurement © 2009, Prentice-Hall,
    • 449. MO Theory• The smaller p-block elements in the second period have a sizeable interaction between the s and p orbitals.• This flips the order of the σ and π molecular orbitals in these Matter And elements. Measurement © 2009, Prentice-Hall,
    • 450. Second-Row MO Diagrams Matter And Measurement © 2009, Prentice-Hall,
    • 451. Chemistry, The Central Science, 11th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten Chapter 10 Gases Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 452. Characteristics of Gases• Unlike liquids and solids, gases – expand to fill their containers; – are highly compressible; – have extremely low densities. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 453. Pressure• Pressure is the amount of force applied to an area. F P= A• Atmospheric pressure is the weight of air per unit of area. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 454. Units of Pressure• Pascals – 1 Pa = 1 N/m2• Bar – 1 bar = 105 Pa = 100 kPa Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 455. Units of Pressure• mm Hg or torr –These units are literally the difference in the heights measured in mm (h) of two connected columns of mercury.• Atmosphere 1.00 atm = 760 torr Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 456. Standard Pressure• Normal atmospheric pressure at sea level is referred to as standard pressure.• It is equal to 1.00 atm 760 torr (760 mm Hg) 101.325 kPa Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 457. Manometer This device is used to measure the difference in pressure between atmospheric pressure and that of a gas in a vessel. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 458. Boyle’s LawThe volume of a fixed quantity of gas atconstant temperature is inversely proportionalto the pressure. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 459. As P and V are inversely proportionalA plot of V versus Presults in a curve.Since PV = k V = k (1/P) This means a plot of V versus 1/P will be Matter And a straight line. Measurement © 2009, Prentice-Hall, Inc.
    • 460. Charles’s Law• The volume of a fixed amount of gas at constant pressure is directly proportional to its absolute temperature.• i.e., V =k T A plot of V versus T will be a straight line. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 461. Avogadro’s Law• The volume of a gas at constant temperature and pressure is directly proportional to the number of moles of the gas.• Mathematically, this means V = kn Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 462. Ideal-Gas Equation• So far we’ve seen that V ∝ 1/P (Boyle’s law) V ∝ T (Charles’s law) V ∝ n (Avogadro’s law)• Combining these, we get nT V∝ P Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 463. Ideal-Gas EquationThe constant ofproportionality isknown as R, thegas constant. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 464. Ideal-Gas EquationThe relationship nT V∝ Pthen becomes nT V=R P or PV = nRT Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 465. Densities of GasesIf we divide both sides of the ideal-gasequation by V and by RT, we get n P = V RT Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 466. Densities of Gases• We know that moles × molecular mass = mass n×Μ=m• So multiplying both sides by the molecular mass (Μ ) gives m PΜ = V RT Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 467. Densities of Gases• Mass ÷ volume = density• So, m PΜ d= = V RTNote: One only needs to know themolecular mass, the pressure, and thetemperature to calculate the density ofa gas. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 468. Molecular MassWe can manipulate the densityequation to enable us to find themolecular mass of a gas: PΜ d= RT Becomes dRT Μ= P Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 469. Dalton’s Law of Partial Pressures• The total pressure of a mixture of gases equals the sum of the pressures that each would exert if it were present alone.• In other words, Ptotal = P1 + P2 + P3 + … Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 470. Partial Pressures• When one collects a gas over water, there is water vapor mixed in with the gas.• To find only the pressure of the desired gas, one must subtract the vapor pressure of Matter water from the total pressure. And Measurement © 2009, Prentice-Hall, Inc.
    • 471. Kinetic-Molecular Theory This is a model that aids in our understanding of what happens to gas particles as environmental conditions change. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 472. Main Tenets of Kinetic- Molecular TheoryGases consist of large numbers ofmolecules that are in continuous,random motion. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 473. Main Tenets of Kinetic- Molecular TheoryThe combined volume of all themolecules of the gas is negligiblerelative to the total volume in which thegas is contained. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 474. Main Tenets of Kinetic- Molecular TheoryAttractive andrepulsive forcesbetween gasmolecules arenegligible. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 475. Main Tenets of Kinetic- Molecular Theory Energy can be transferred between molecules during collisions, but the average kinetic energy of the molecules does not change with time, as long as the temperature of the gas remains constant. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 476. Main Tenets of Kinetic- Molecular TheoryThe average kineticenergy of themolecules isproportional to theabsolutetemperature. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 477. Effusion Effusion is the escape of gas molecules through a tiny hole into an evacuated space. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 478. EffusionThe difference in the rates of effusion forhelium and nitrogen,for example,explains a heliumballoon woulddeflate faster. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 479. DiffusionDiffusion is thespread of onesubstancethroughout a spaceor throughout asecond substance. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 480. Grahams Law KE1 = KE2 1/2 m1v12 = 1/2 m2v22 m1 v 22 = m2 v 12√m1 √v22 = v2 =√m2 √v1 2 v1 Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 481. Real Gases In the real world, the behavior of gases only conforms to the ideal-gas equation at relatively high temperature and low pressure. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 482. Real GasesEven the same gaswill show wildlydifferent behaviorunder high pressureat differenttemperatures. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 483. Deviations from Ideal BehaviorThe assumptions made in the kinetic-molecularmodel (negligible volume of gas moleculesthemselves, no attractive forces between gasmolecules, etc.) break down at high pressure Matter Andand/or low temperature. Measurement © 2009, Prentice-Hall, Inc.
    • 484. Corrections for Nonideal Behavior• The ideal-gas equation can be adjusted to take these deviations from ideal behavior into account.• The corrected ideal-gas equation is known as the van der Waals equation. Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 485. The van der Waals Equation n 2a (P + 2 ) (V − nb) = nRT V Matter And Measurement © 2009, Prentice-Hall, Inc.
    • 486. Chapter 11Intermolecular Forces, Liquids, and Solids Matter And Measurement © 2009, Prentice-Hall,
    • 487. States of MatterThe fundamental difference between states ofmatter is the distance between particles. Matter And Measurement © 2009, Prentice-Hall,
    • 488. States of MatterBecause in the solid and liquid statesparticles are closer together, we refer to themas condensed phases. Matter And Measurement © 2009, Prentice-Hall,
    • 489. The States of Matter • The state a substance is in at a particular temperature and pressure depends on two antagonistic entities: – the kinetic energy of the particles; – the strength of the attractions between the particles. Matter And Measurement © 2009, Prentice-Hall,
    • 490. Intermolecular ForcesThe attractions between molecules are notnearly as strong as the intramolecularattractions that hold compounds together. Matter And Measurement © 2009, Prentice-Hall,
    • 491. Intermolecular ForcesThey are, however, strong enough to controlphysical properties such as boiling andmelting points, vapor pressures, andviscosities. Matter And Measurement © 2009, Prentice-Hall,
    • 492. Intermolecular ForcesThese intermolecular forces as a group arereferred to as van der Waals forces. Matter And Measurement © 2009, Prentice-Hall,
    • 493. van der Waals Forces• Dipole-dipole interactions• Hydrogen bonding• London dispersion forces Matter And Measurement © 2009, Prentice-Hall,
    • 494. Ion-Dipole Interactions• Ion-dipole interactions (a fourth type of force), are important in solutions of ions.• The strength of these forces are what make it possible for ionic substances to dissolve in polar solvents. Matter And Measurement © 2009, Prentice-Hall,
    • 495. Dipole-Dipole Interactions • Molecules that have permanent dipoles are attracted to each other. – The positive end of one is attracted to the negative end of the other and vice- versa. – These forces are only important when the molecules are close to each other. Matter And Measurement © 2009, Prentice-Hall,
    • 496. Dipole-Dipole InteractionsThe more polar the molecule, the higheris its boiling point. Matter And Measurement © 2009, Prentice-Hall,
    • 497. London Dispersion ForcesWhile the electrons in the 1s orbital of heliumwould repel each other (and, therefore, tendto stay far away from each other), it doeshappen that they occasionally wind up on thesame side of the atom. Matter And Measurement © 2009, Prentice-Hall,
    • 498. London Dispersion ForcesAt that instant, then, the helium atom is polar,with an excess of electrons on the left sideand a shortage on the right side. Matter And Measurement © 2009, Prentice-Hall,
    • 499. London Dispersion ForcesAnother helium nearby, then, would have adipole induced in it, as the electrons on theleft side of helium atom 2 repel the electronsin the cloud on helium atom 1. Matter And Measurement © 2009, Prentice-Hall,
    • 500. London Dispersion ForcesLondon dispersion forces, or dispersionforces, are attractions between aninstantaneous dipole and an induced dipole. Matter And Measurement © 2009, Prentice-Hall,
    • 501. London Dispersion Forces• These forces are present in all molecules, whether they are polar or nonpolar.• The tendency of an electron cloud to distort in this way is called polarizability. Matter And Measurement © 2009, Prentice-Hall,
    • 502. Factors Affecting London Forces • The shape of the molecule affects the strength of dispersion forces: long, skinny molecules (like n-pentane tend to have stronger dispersion forces than short, fat ones (like neopentane). • This is due to the increased surface area in n-pentane. Matter And Measurement © 2009, Prentice-Hall,
    • 503. Factors Affecting London Forces• The strength of dispersion forces tends to increase with increased molecular weight.• Larger atoms have larger electron clouds which are easier to polarize. Matter And Measurement © 2009, Prentice-Hall,
    • 504. Which Have a Greater Effect?Dipole-Dipole Interactions or Dispersion Forces• If two molecules are of comparable size and shape, dipole-dipole interactions will likely the dominating force.• If one molecule is much larger than another, dispersion forces will likely determine its physical properties. Matter And Measurement © 2009, Prentice-Hall,
    • 505. How Do We Explain This? • The nonpolar series (SnH4 to CH4) follow the expected trend. • The polar series follows the trend from H2Te through H2S, but water is quite an anomaly. Matter And Measurement © 2009, Prentice-Hall,
    • 506. Hydrogen Bonding• The dipole-dipole interactions experienced when H is bonded to N, O, or F are unusually strong.• We call these interactions hydrogen bonds. Matter And Measurement © 2009, Prentice-Hall,
    • 507. Hydrogen Bonding • Hydrogen bonding arises in part from the high electronegativity of nitrogen, oxygen, and fluorine.Also, when hydrogen is bonded to one of thosevery electronegative elements, the hydrogennucleus is exposed. Matter And Measurement © 2009, Prentice-Hall,
    • 508. Summarizing Intermolecular Forces Matter And Measurement © 2009, Prentice-Hall,
    • 509. Intermolecular Forces Affect Many Physical Properties The strength of the attractions between particles can greatly affect the properties of a substance or solution. Matter And Measurement © 2009, Prentice-Hall,
    • 510. Viscosity• Resistance of a liquid to flow is called viscosity.• It is related to the ease with which molecules can move past each other.• Viscosity increases with stronger intermolecular forces and decreases with higher temperature. Matter And Measurement © 2009, Prentice-Hall,
    • 511. Surface Tension Surface tension results from the net inward force experienced by the molecules on the surface of a liquid. Matter And Measurement © 2009, Prentice-Hall,
    • 512. Solids• We can think of solids as falling into two groups: – crystalline, in which particles are in highly ordered arrangement. Matter And Measurement © 2009, Prentice-Hall,
    • 513. Solids • We can think of solids as falling into two groups: – amorphous, in which there is no particular order in the arrangement of particles. Matter And Measurement © 2009, Prentice-Hall,
    • 514. Crystalline Solids Because of the ordered in a crystal, we can focus on the repeating pattern of arrangement called the unit cell. Matter And Measurement © 2009, Prentice-Hall,
    • 515. Crystalline SolidsThere are several types of basicarrangements in crystals, like the onesdepicted above. Matter And Measurement © 2009, Prentice-Hall,
    • 516. Crystalline SolidsWe can determinethe empiricalformula of an ionicsolid by determininghow many ions ofeach element fallwithin the unit cell. Matter And Measurement © 2009, Prentice-Hall,
    • 517. Ionic Solids• What are the empirical formulas for these compounds? – (a) Green: chlorine; Gray: cesium – (b) Yellow: sulfur; Gray: zinc – (c) Gray: calcium; Blue: fluorine (a) (b) (c) Matter CsCl ZnS CaF2 And Measurement © 2009, Prentice-Hall,
    • 518. Matter AndMeasurement
    • 519. Matter AndMeasurement
    • 520. Matter AndMeasurement
    • 521. Attractions in Ionic Crystals In ionic crystals, ions pack themselves so as to maximize the attractions and minimize repulsions between the ions. Matter And Measurement © 2009, Prentice-Hall,
    • 522. Types of Bonding in Crystalline Solids Matter And Measurement © 2009, Prentice-Hall,
    • 523. Covalent-Network and Molecular Solids• Diamonds are an example of a covalent- network solid, in which atoms are covalently bonded to each other. – They tend to be hard and have high melting points. Matter And Measurement © 2009, Prentice-Hall,
    • 524. Covalent-Network and Molecular Solids• Graphite is an example of a molecular solid, in which atoms are held together with van der Waals forces. – They tend to be softer and have lower melting points. Matter And Measurement © 2009, Prentice-Hall,
    • 525. Metallic Solids• Metals are not covalently bonded, but the attractions between atoms are too strong to be van der Waals forces.• In metals valence electrons are delocalized throughout the solid. Matter And Measurement © 2009, Prentice-Hall,
    • 526. Phase Changes Matter And Measurement © 2009, Prentice-Hall,
    • 527. Energy Changes Associated with Changes of StateThe heat of fusion is the energy required tochange a solid at its melting point to a liquid. Matter And Measurement © 2009, Prentice-Hall,
    • 528. Energy Changes Associated with Changes of StateThe heat of vaporization is defined as theenergy required to change a liquid at itsboiling point to a gas. Matter And Measurement © 2009, Prentice-Hall,
    • 529. Energy Changes Associated with Changes of State • The heat added to the system at the melting and boiling points goes into pulling the molecules farther apart from each other. • The temperature of the substance does not rise during a phase change. Matter And Measurement © 2009, Prentice-Hall,
    • 530. Vapor Pressure• At any temperature some molecules in a liquid have enough energy to escape.• As the temperature rises, the fraction of molecules that have enough energy to escape increases. Matter And Measurement © 2009, Prentice-Hall,
    • 531. Vapor Pressure As more molecules escape the liquid, the pressure they exert increases. Matter And Measurement © 2009, Prentice-Hall,
    • 532. Vapor Pressure The liquid and vapor reach a state of dynamic equilibrium: liquid molecules evaporate and vapor molecules condense at the same rate. Matter And Measurement © 2009, Prentice-Hall,
    • 533. Vapor Pressure• The boiling point of a liquid is the temperature at which it’s vapor pressure equals atmospheric pressure.• The normal boiling point is the temperature at which its vapor pressure is 760 torr. Matter And Measurement © 2009, Prentice-Hall,
    • 534. Phase DiagramsPhase diagrams display the state of asubstance at various pressures andtemperatures and the places where equilibriaexist between phases. Matter And Measurement © 2009, Prentice-Hall,
    • 535. Phase Diagrams• The circled line is the liquid-vapor interface.• It starts at the triple point (T), the point at which all three states are in equilibrium. Matter And Measurement © 2009, Prentice-Hall,
    • 536. Phase DiagramsIt ends at the critical point (C); above thiscritical temperature and critical pressure theliquid and vapor are indistinguishable fromeach other. Matter And Measurement © 2009, Prentice-Hall,
    • 537. Phase DiagramsEach point along this line is the boiling pointof the substance at that pressure. Matter And Measurement © 2009, Prentice-Hall,
    • 538. Phase Diagrams• The circled line in the diagram below is the interface between liquid and solid.• The melting point at each pressure can be found along this line. Matter And Measurement © 2009, Prentice-Hall,
    • 539. Phase Diagrams• Below the triple point the substance cannot exist in the liquid state.• Along the circled line the solid and gas phases are in equilibrium; the sublimation point at each pressure is along this line. Matter And Measurement © 2009, Prentice-Hall,
    • 540. Phase Diagram of Water • Note the high critical temperature and critical pressure. – These are due to the strong van der Waals forces between water molecules. Matter And Measurement © 2009, Prentice-Hall,
    • 541. Phase Diagram of Water • The slope of the solid- liquid line is negative. – This means that as the pressure is increased at a temperature just below the melting point, water goes from a solid to a liquid. Matter And Measurement © 2009, Prentice-Hall,
    • 542. Phase Diagram of Carbon Dioxide Carbon dioxide cannot exist in the liquid state at pressures below 5.11 atm; CO2 sublimes at normal pressures. Matter And Measurement © 2009, Prentice-Hall,
    • 543. Phase Diagram of Carbon Dioxide The low critical temperature and critical pressure for CO2 make supercritical CO2 a good solvent for extracting nonpolar substances (like caffeine) Matter And Measurement © 2009, Prentice-Hall,