If this is table salt, what is the identity of the positive and negative ions in question? What is the fundamental difference between a sodium ion and a sodium atom? It is very hard for us to prove to you in a classroom setting that this is really what is behind all the matter that we observe everyday, so you will have to believe it to me true, and use your imagination. The ions are stuck together strongly and “do not move”. This is why what we observe by eye is a solid substance
The tumbling and movement of the molecules at the molecular level results in what we see as a liquid substance.
You can think of the solute as a “rock star”, and the water molecules are the millions of crazy teenage fans. As soon as the solute is placed in the water, the molecules go nuts and as quickly as possible surround the salt and pull apart the individual ions. Silberberg 2 nd Ed movie resource #18
There are no charged chemical species in this sugar solution
Solutions do not have to be aqueous based. For example, gasoline is a solution that is a mixture of hydrocarbon compounds, where the quantity of octane determines the quality of the gasoline. There is NO water in gasoline!
A: 10.38 B: 25.47 C: 6.0 D: 1.0168
105.4 90.510 0.0201 4500
I Have No Bright Or Clever Friends Tip for molecules: a molecular compound should NOT have a metal element in the chemical formula
Show movie from Silberberg CD resource: #14 Figure: 03-01 Title: The Formation of an Ionic Compound Caption: An atom of sodium (a metal) loses an electron to an atom of chlorine (a nonmetal), creating a pair of oppositely charged ions. The sodium cation is then attracted to the chloride anion and the two are held together as part of a crystalline lattice.
The octet rule explains why main group elements form the ions that they do during reaction to form a compound.
Figure: 03-04 Title: Molecular Elements Caption: The highlighted elements exist primarily as diatomic molecules (yellow) or polyatomic molecules (red). The “staircase” separates the non-metal elements (to the right of the staircase) from the metal elements (left of staircase). The one exception is hydrogen, which is a non-metal element.
Most well known ionic compound: NaCl – sodium chloride Understand the “base name” Eg. CsF, Al2S3 why not dialuminum trisulfide Main competency of course is name formula: rubidium oxide, calcium phosphide Iron – Fe, can be Fe3+ iron III ferric or Fe2+ iron II ferrous FeCl2 FeCl3 Copper – Cu Cu2+ or Cu+ Eg. TiCl4, PbBr2, Fe2S3 Cu(I) oxide, lead(IV) chloride, maganese (IV) sulfide
Copper sulfate pentahydrate CoCl2 – 6 H2O
H2O Dinitrogen tetroxide CrO3 CO2
HCl example HNO3 HNO2 “ exception”: sulfuric acid
Nyb F09 Unit 1 Slides 1 36
Pertinent Info • Instructor Name: Tom (Tian-Yun) Wang • Email Address: email@example.com • Room #: H-253 • Local Telephone: 5879 • Office Hours: See Handout • Primary Method for Contact: Messaging in Omnivox (MIO)
Quizzes and Assignments • Approximately 5 quizzes will be given throughout the semester, each worth 2% of your final grade. Tentative schedule coming shortly. • Assignments will be given using an internet based system called “ LON-CAPA”, all worth 5% of your final grade. More on how to access this system later. • For more practice with chemistry questions, Problem Sets will be posted online. Completion of these problems are purely optional and do not account for marks
Lecture Style and Note Access • Powerpoint slides are used for main facts and diagrams, but often lacks details and explanations • You do not need to write what is on the slide. It will be much more useful to take notes on what I am saying/explaining • I will try to get the slides to you in advance of the class online in “Lea”, the Omnivox Classroom. • Go to “Distributed Documents”, click on file and save to your computer. • The rest is up to you in terms of organization • Work will still be done directly on chalkboard
Finding Motivation As a Student The amount of motivation you have for school is important in your success but also important is the kind of motivation that you have. 1. Intrinsic Motivation - Participating in an activity for itself and for the pleasure derived from the participation • Obtaining knowledge: “I experience pleasure and satisfaction from learning new things” • Experiencing stimulation: “I feel intellectually stimulated from the class” • Sense of accomplishment: “I feel satisfaction from completing difficult academic activities
2. Extrinsic Motivation - Engaging in an activity as a means to an end, and not for its own sake • Identification: “I think that a college education will help me better prepare for the career I am pursuing.” • Introjection: “To show myself that I am an intelligent person.” • External regulation: “In order to obtain a more prestigious job later on.” 3. Amotivation - Uninterested and unsure as to why you are engaging in activities.
Why Do Some Students Struggle With Chemistry? • Chemistry is often called “The Central Science”. This is because its main focus is the study of matter, which is essentially anything and everything ! Chemistry is connected and related to all other natural sciences. • In order to understand matter, we must understand what it is made of at the atomic/molecular level. I believe that some students struggle with chemistry because of the visual disconnect they have between what they physically see, and what the matter actually looks like at the atomic/molecular level.
Granule of table salt 3-D “ lattice” of gajillions of alternating positive and negative ions An ionic compound • The ions are stuck together strongly due to attractive electrostatic forces.
A molecular (covalent) compound Granules of table sugar (sucrose) Gajillions of sugar molecules packed closely together. C 12 H 22 O 11 • The atoms of the sugar molecule are held together by covalent bonds. Each sugar molecule “sticks to another through attractive forces.
Glass of pure water Gajillions of water molecules tumbling about each other H 2 O O H H
Solid NaCl Aqueous Na + and Cl - ion solution When ionic compounds are placed in water, the water molecules can pull the ions apart. The ions have dissociated
= When most molecular compounds are placed in water, the water molecules pull only the intact sugar molecules apart. No covalent bonds are broken! Solid sugar Aqueous sugar solution
• Solution: A homogeneous (uniform) mixture composed of two or more substances, typically a solvent and a solute • Solvent: The substance in a solution that does the dissolving • Solute: The substance in a solution that is being dissolved Definitions In this course, we deal primarily with solutions that are aqueous , meaning that the solvent is water .
Measurement and Significant Figures (Ch. 1.6-1.8) • In science, it is important to report data with as much certainty as possible. The more significant figures (digits) a number has, the greater its certainty. The amount of significant figures you can record from a measurement depends on the accuracy of the device. 1. A digital instrument provides a definite amount of certainty. - A balance that reads 35.126 g gives 3 decimal places of certainty, and all digits are significant - If the balance reads 100.000 g, all 6 digits must be reported
2. An analog device (scaled) is more complicated when it comes to significant figures - The amount of certainty provided by these types of devices depends on how many incremental markings there are. You must report all digits that are absolutely certain, PLUS a last digit which is estimated
10.0 11.0 25.3 25.4 25.5 25.6 3 4 5 6 1.014 1.015 1.016 1.018 1.017 7 A B C D
• Counting Significant Figures (sig. figs.) <ul><li>All non-zero digits are significant </li></ul><ul><ul><li>1.5 has 2 sig. figs. </li></ul></ul><ul><li>Interior zeros are significant </li></ul><ul><ul><li>1.05 has 3 sig. figs. </li></ul></ul><ul><li>Leading zeros are NOT significant </li></ul><ul><ul><li>0.001050 has 4 sig. figs </li></ul></ul><ul><li>Trailing zeros may or may not be significant </li></ul><ul><ul><li>a) Trailing zeros after a decimal point are significant </li></ul></ul><ul><ul><ul><li>- 1.050 has 4 sig. figs. </li></ul></ul></ul><ul><ul><li>b) Zeros at the end of a number without a written </li></ul></ul><ul><ul><li>decimal point are ambiguous and should be avoided </li></ul></ul><ul><ul><li>by using scientific notation </li></ul></ul><ul><ul><ul><li>- 150 has 2 sig. figs. then 1.5 x 10 2 </li></ul></ul></ul><ul><ul><ul><li>- but if 150 has 3 sig. figs. then 1.50 x 10 2 </li></ul></ul></ul>
• Adding and Subtracting Sig Figs. When adding or subtracting measurements with significant figures, the result has the same number of decimal places as the measurement with the fewest number of decimal places • Multiplying or Dividing Sig Figs. When multiplying or dividing measurements with significant figures, the result has the same number of significant figures as the measurement with the fewest number of significant figures • Exact Numbers: they have no uncertainty and thus have no impact on sig fig calculations Eg. Discrete numbers, defined quantities, and integral parts of an equation
Classification of Matter (Ch. 1) • Atom : Atoms are submicroscopic particles that constitute the fundamental building blocks of matter. The structure of an atom consists of a nucleus of neutral particles called neutrons (n o ), and positively charged particles called protons (p + ), which is surrounded by a cloud of negatively charged particles called electrons (e - ). nucleus Electron cloud “ Realistic” Atom “ Cartoony” Atom An atom that has gained or lost an electron(s) is called an ion
• Element : A substance that cannot be broken down into simpler substances. An element consists of only one type of atom . • Compound: a type of matter composed of two or more different elements (atoms) that are chemically bound together. There are 7 elements that exists as diatomic molecules • Molecule: an independent structural unit consisting of two or more atoms that are chemically bound together. The atoms bound together can be the same, or different. • Substance (pure substance): forms of matter with fixed composition. All items above have fixed compositions, and therefore are all considered to be substances
• Mixture: something that consists of two or more substances that are only physically intermingled. The ratio of different substances in a mixture is not fixed - Homogeneous mixture : a mixture that is uniform in appearance and has the same physical properties throughout. - Heterogeneous mixture: a mixture that is non-uniform consisting of 2 or more physically distinct phases.
Physical States of Matter • Solid : at a molecular level, the particles making up the solid are close together, highly organized and have little motion, giving the solid a physical shape that does not change. Solids have definite volume and have a surface • Liquid : the particles are close together but have motion, tumbling about each other, and therefore its physical shape can change to fill the shape of its container. It has definite volume, and can create a surface • Gas : the particles are far apart, disorganized, and moving rapidly, allowing gases to expand to fill its container (diffusion). Gases have no definite shape and volume, and therefore do not create a surface
Gases are compressible, whereas solids and liquids are not, due to the tight packing of the particles
Compounds and Chemical Bonding (Ch. 3) • Ionic Compounds : consist of a positively charged ion ( cation ) and a negatively charged ion ( anion ). Ionic compounds are typically formed from the reaction of a metal element with a non-metal element. All ionic compounds are solids , and consist of 3-D lattices of alternating ions The force holding the ions together is called an ionic “bond”. (But it’s really more of a force than a bond)
- During the reaction to form an ionic compound, the metal atoms lose electrons to the non-metal atom to become cations . • Electron Transfer • Valence Electrons of Main Group Elements <ul><li>Valence electrons are the electrons of an element/atom </li></ul><ul><li>in the outermost “shell” of the atom. </li></ul>- In Main Group elements (1A-8A), the number of valence electrons matches the group number. During formation of a compound, the atoms gain or lose electrons to look similar in electron structure to the stable, noble gases in the 8th group of the periodic table octet rule - The non-metal atoms gain electrons becoming anions
• Molecular (Covalent) Compounds : Formed from non- metal atoms covalently bonded together. Valence electrons between atoms are shared to form the covalent bond Molecular compounds are extremely varied in their physical nature. A single molecule can be as simple as consisting of 2 atoms, to thousands of atoms in proteins, or millions of atoms in a strand of DNA. Hemoglobin Portion of DNA
Chemical Nomenclature (Ch. 3.5) • Binary Ionic Compounds : - If a transition metal is present that can form more than one type of cation charge - If a polyatomic ion is present, the name of the polyatomic ion is simply stated followed by the name of the cation • Ionic Compounds Containing Polyatomic Ions :
• Monatomic Ions : Ion species consisting of 1 atom • Polyatomic Ions : Ion species consisting of two or more atoms that are covalently bonded together and have net positive or negative charge. For this course we will require you to memorize the chemical formula and charge of 11 common polyatomic ions - Nitrate - Nitrite - Sulfate - Sulfite - Carbonate - Bicarbonate or hydrogen carbonate - Hydroxide - Perchlorate - Phosphate - Acetate - Ammonium
• Hydrated Ionic Compounds : - Some ionic compounds trap water molecules within their 3-D lattice - A certain number of water molecules are associated with each formula unit of the ionic compound, and is denoted using a Greek prefix followed by the word hydrate (all in one word) • Greek prefixes from 1 – 10 : mono, di, tri, tetra, penta, hexa, hepta, octa, nona and deca (if ½ of a hydrate “hemi”) Eg. Magnesium sulfate heptahydrate MgSO 4 • 7H 2 O Dot after compound denotes waters of hydration
• Binary Molecular Compounds : - 1 st element is the one that is most left and down in the periodic table - Keep in mind that although the 2 nd element gets an “ ide” ending, it is not an ion . - If the number of 1 st element atoms is 1, the “mono” prefix is left out.
• Naming Acids (Inorganic Acids) - Binary Acids: Composed of hydrogen and a non-metal - Oxyacid (Oxoacid): Contain hydrogen and an oxyanion , which is a polyatomic ion consisting of a non-metal and oxygen - If oxyanion ends in –ate: - If oxyanion ends in –ite:
- Avogadro hypothesized that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. This hypothesis is known as Avogadro’s Law . 1 mole = 6.022 x 10 23 entities (atoms, molecules, units, etc) But Why? <ul><li>Carbon is regarded as the most significant element since all </li></ul><ul><li>life is based on this atom. Scientist standardized the mole </li></ul><ul><li>to be equal to the number of atoms in exactly 12.00 grams </li></ul><ul><li>of pure carbon-12 (which is 6.022 x 10 23 atoms) </li></ul>The Mole Concept (Ch. 2) - This number is called Avogadro’s number to honor the man who first made the connection of equal quantities of particles for a certain quantity of substance
Formula Mass (Ch. 3) • The Periodic Table of Elements: Atomic number Symbol Name Atomic mass The atomic mass represents the mass of one atom of the element, and is given units called “atomic mass units” or amu . - A compound’s mass can be approximated by adding together the atomic masses of all atoms in the chemical formula Ionic Compounds Formula mass or formula weight Molecular Compounds Molecular mass or molecular weight - Molar mass : the mass of a substance per mole (g/mol) 11 Na Sodium 22.99
Aqueous Solution Chemistry (Ch. 4) Water is a polar molecule, meaning one end has more negative charge character, and the other end has more positive charge character. - Water can create favorable interactions with substances that are also polar or charged, such as ionic compounds.
- If an ionic compound is soluble in water, it is because the water molecules slowly “take apart” and surround each individual ion.