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Chem unit 6 presentation

  1. 1. Ionic Compounds and Metals Chemistry Unit 6
  2. 2. Main IdeasIons are formed when atoms gain or lose valenceelectrons to achieve a stable octet electronconfiguration.Oppositely charged ion attract each other, formingelectrically neutral ionic compounds.In written names and formulas for ioniccompounds, the cation appears first, followed bythe anion.Metals form crystal lattices and can be modeled ascations surrounded by a “sea’” of freelymoving valence electrons.
  3. 3. Ion FormationIons are formed when atoms gain or lose valence electrons to achieve a stable octet electron configuration.Goals and Objectives: Define a chemical bond. Describe the formation of positive and negative ions. Relate ion formation to electron configuration.
  4. 4. Valence Electrons and Chemical BondsChemical Bond – is a force that holds twoatoms together. They can form between the positive nucleus of one atom and the negative valence electrons of another atom or between two oppositely charged ions.
  5. 5. Valence Electrons and Chemical BondsAtom’s try to form the octet – the stablearrangement of eight valence electrons in theouter energy level – by gaining or losingvalence electrons.The transfer of valence electrons betweentwo atoms is based on the ionization energyand electron affinity of the two atoms. Noble gases- high ionization energy + low electron affinity = little chemical reactivity.
  6. 6. Positive Ion FormationCation – positively charged ion Example: Sodium atom: 1s2 2s2p6 3s1 Sodium ion: 1s2 2s2 p6 = neon
  7. 7. Positive Ion FormationMetal atoms are reactive because they losevalence electrons easily. Group 1: commonly form +1 ions Group 2: commonly form +2 ions Group 13: sometimes +3 ions
  8. 8. Positive Ion FormationTransition metal ions have an outer shell of s2 They will lose their s electrons and occasionally a d electron. Typically form +2 or +3 ions but can form greater than +3 ions
  9. 9. Positive Ion FormationOther relatively stable electron arrangementsare referred to as pseudo-noble gasconfigurations. Groups 11-14 will lose electrons to form full outer shells: s, p, and d.
  10. 10. Negative Ion FormationAn anion is a negatively charged ion. (Add “-ide” to the end of the root atom name.) Nonmetals easily gain electrons. Example: Chlorine atom: 1s2 2s2p6 3s2p5 Chlorine ion: 1s2 2s2p6 3s2p6 = Argon
  11. 11. Negative Ion FormationNonmetal ions gain the number of electronsrequired to fill an octet.Some nonmetals can gain or lose electrons tocomplete an octet. Phosphorus can gain 3 or lose 5 Group 15 usually gains 3 electrons Group 16 usually gains 2 electrons Group 17 usually gains 1 electron
  12. 12. Practice ProblemsCALM 6:1
  13. 13. Ionic Bonds and Ionic Compounds
  14. 14. Ionic Bonds and Ionic CompoundsOppositely charged ions attract each other, formingelectrically neutral ionic compounds.Goals and Objectives: Describe the formation of ionic bonds and the structureof ionic compounds. Generalize about the strength of ionic bonds based onthe physical properties of ionic compounds. Categorize ionic bond formation as exothermic orendothermic.
  15. 15. Ionic BondIonic Bond is the electrostatic force thatholds oppositely charged particles together.Ionic Compound is a compound that containsan ionic bond. Ionic bonds between metals and oxygen are called oxides. Most other ionic compounds are considered salts.
  16. 16. Binary Ionic CompoundBinary Ionic compound is an ionic compoundthat contains two different elements. One metallic cation and a nonmetallic anion. Examples: NaCl, MgO, KBr, LiF
  17. 17. Ionic Bond FormationElectrons gained and lost in each elementmust be equal. (conservation of electrons) Calcium and Fluorine Aluminum and Oxygen Sodium and Chlorine
  18. 18. Properties of Ionic CompoundsCompounds are organized such that a patternrepeats to balance attraction and repulsionTotal charge of a compound is neutralOften highly organizedExample: NaCl crystal
  19. 19. Crystal LatticeA crystal lattice is a three dimensionalgeometric arrangement of particles. Each negative ion is surrounded by a positive ion which results in strong attractions between ions. Size and shape are dependent on relative numbers of ions.
  20. 20. Crystal LatticePhysical Properties: Characteristics of bond strength – ionic bonds are relatively strong and take a large amount of energy to break. Melting point – high Boiling point – high Hardness of material is high: rigid and brittle solids.
  21. 21. Properties of Ionic Compounds
  22. 22. Crystal LatticeCharacteristics of the compound: Conducts electricity, conditionally Ions in solid state ionic compounds are locked in place and they do not have free electrons in order to conduct electricity. Ionic compounds that are melted or dissolved in aqueous solutions have ions that are free to move and therefore do conduct electricity Electrolyte – an ionic compound that conducts electricity in an aqueous solution.
  23. 23. Energy and the Ionic BondFormation of ionic compounds forms amore stable system and therefore reducesthe energy required to sustain it. Since the creating of bonds lowers energy, energy is released in the process. The creation of bonds is said to be Exothermic. Exothermic – energy is released during a chemical reaction.
  24. 24. Energy and the Ionic BondBreaking of ionic compounds reduces thestability of a system and therefore increasesthe energy required to sustain it . Since the creating of bonds lowers energy, the breaking of bonds increases energy and therefore it is required for the process. Endothermic – energy is absorbed during a chemical reaction.
  25. 25. Lattice EnergyLattice energy is the energy required to separate 1mole of the ions of an ionic compound. higher the lattice energy the stronger the bond strength. Directly related to the size of the ions bonded. smaller ions form compounds more closely because attraction increases with decreased distance. Also affected by charge of ions Higher ion charge typically has higher lattice energy.
  26. 26. Lattice Energy Q1Q2 Lattice µ r
  27. 27. Practice ProblemsCALM 6:2
  28. 28. Names and Formulasfor Ionic Compounds
  29. 29. Names and Formulas for Ionic CompoundsIn written names and formulas for ionic compounds, thecation appears first, followed by the anion.Goals and Objectives: Relate a formula unit of an ionic compound to itscomposition. Write formulas for ionic compounds and oxyanions. Apply naming conventions to ionic compounds andoxyanions.
  30. 30. Formulas for Ionic CompoundsA standardized system for naming compoundswas developed for much the same reason as theSI unit system. This serves as a universal namingsystem for communication among the sciencecommunity.
  31. 31. Formula UnitA formula unit is the chemical formula for an ioniccompound and represents the simplest ratio ofions. MgCl2 not Mg4Cl8A monoatomic ion is a one atom ion.
  32. 32. Oxidation numberOxidation number (oxidation state) thecharge of a monatomic ion.
  33. 33. Formulas for Ionic CompoundsThe symbol for the cation is written first withthe anion second.Subscripts represent the number of atoms ofeach element in a compound.The total charge must equal zero in an ioniccompound.
  34. 34. Polyatomic IonsPolyatomic ions are made up of more than oneatom.Formulas for polyatomic ionic compounds Charge applies to the entire group of atoms. Parentheses are used if more than one polyatomic ion is needed to balance a compound. Do not change subscripts within the ion group Example (NH4)O
  35. 35. Polyatomic Ions
  36. 36. OxyanionAn oxyanion is a polyatomic negative ioncomposed of an element, usually anonmetal, bonded to one or more oxygen.
  37. 37. Oxyanion Naming Rules
  38. 38. Names for Ions and Ionic Compounds1. Name the cation followed by the anion.2. For monatomic cations, use the element name.3. For monatomic anions, use the root of the element with the suffix –ide.
  39. 39. Names for Ions and Ionic Compounds4. Multiple oxidation states are represented by a Roman numeral in paranthesis after the cation. a) This applies to transition metals with more than one oxidation state and not the Group 1 and 2 cations. b) Example: FeO is Iron (II) oxide; Fe2O3 Iron (III) oxide.5. With a polyatomic ion, name the cation followed by the name of the polyatomic ion. a) Example: NaOH is sodium hydroxide.
  40. 40. Problem Solving
  41. 41. Practice ProblemsCALM 6:3
  42. 42. Metallic Bonds and the Properties of Metals
  43. 43. Metallic Bonds and the Properties of MetalsMetals form crystal lattices and can be modeled ascations surrounded by a “sea” of freely moving valenceelectrons.Goals and Objectives: Describe a metallic bond. Relate the electron sea model to the physicalproperties of metals. Define alloys, and categorize them into two basictypes.
  44. 44. MetalsMetals are not ionic but share several propertieswith ionic compounds.Metals also form lattices in the solidstate, where 8 to 12 other atoms closelysurround each metal atom. Within the crowded lattice, the outer energy levels of metal atoms overlap.
  45. 45. Electron Sea ModelThe electron sea model proposes that all metal atoms in a metallic solid contribute their valence electrons to form a "sea" of electron. The electrons are free to move around and are referred to as delocalized electrons, forming a metallic cation.
  46. 46. Metallic BondsA metallic bondis the attraction of an metallic cation for delocalized electrons
  47. 47. Properties of MetalsBoiling points are much more extreme thanmelting points because of the energyrequired to separate atoms from the groupsof cations and electrons.
  48. 48. Properties of MetalsMetals are malleable because they can behammered into sheets.Metals are ductile because they can be drawninto wires.
  49. 49. Properties of MetalsMobile electrons around cations make metalsgood conductors of electricity and heat.As the number of delocalized electronsincreases, so does hardness and strength.
  50. 50. Metal AlloysAn alloy is a mixture of elements that has metallic properties. The properties of alloys differ from the elements they contain.
  51. 51. Metal Alloys
  52. 52. Metal AlloysSubstitutional alloys are formed when someatoms in the original metallic solid arereplaced by other metals of similar atomicstructure.Interstitial alloys are formed when smallholes in a metallic crystal are filled withsmaller atoms.
  53. 53. Practice ProblemsCALM 6:4
  54. 54. Accumulating ContentHow does the electron configuration of a neutralelement compare to that of its ion configuration?
  55. 55. Accumulating ContentHow does energy and stability relate to ionformation and bond formation?
  56. 56. Accumulating ContentWhat are some physical and chemical properties ofmetals that are caused by the way they ionize orbond?
  57. 57. Study Guide Key Concepts
  58. 58. Key ConceptsA chemical bond is the force that holds two atomstogether.Some atoms form ions to gain stability. This stableconfiguration involves a complete outer energylevel, usually consisting of eight valenceelectrons.Ions are formed by the loss or gain of valenceelectrons.
  59. 59. Key ConceptsThe number of protons remains unchanged duringion formation.Ionic compounds contain ionic bonds formed bythe attraction of oppositely charged ions.Ions in an ionic compound are arranged in arepeating pattern known as a crystal lattice
  60. 60. Key ConceptsIonic compound properties are related toionic bond strength.Ionic compounds are electrolytes; theyconduct an electric current in the liquid phaseand in aqueous solution.Lattice energy is the energy needed toremove 1 mol of ions from its crystal lattice.
  61. 61. Key ConceptsA formula unit gives the ratio of cations toanions in the ionic compound.A monatomic ion is formed from one atom.The charge of a monatomic ion is itsoxidation number.Roman numerals indicate the oxidationnumber of cations having multiple possibleoxidation states.
  62. 62. Key ConceptsPolyatomic ions consist of more than oneatom and act as a single unit.To indicate more than one polyatomic ion in achemical formula, place parentheses aroundthe polyatomic ion and use a subscript.A metallic bond forms when metal cationsattract freely moving, delocalized valenceelectrons.
  63. 63. Key ConceptsIn the electron sea model, electrons movethrough the metallic crystal and are not heldby any particular atom.The electron sea model explains the physicalproperties of metallic solids.Metal alloys are formed when a metal ismixed with one or more other elements.
  64. 64. QuestionsCations form when atoms _______ electrons.A.gainB.loseC.chargeD.delocalize
  65. 65. QuestionsWhat is the repeating pattern of atoms in an ionic solid called?A.crystal latticeB.ionic latticeD.ionic bonding
  66. 66. QuestionsGive the name of the following: NaClO4A.sodium hypochloriteB.sodium chloriteC.sodium chlorateD.sodium perchlorate
  67. 67. QuestionsAs the distance between ions in an ionic bond is shortened,A.the energy to break the bond decreases.B.the electrostatic attraction decreases.C.the electrostatic attraction increases.D.the ionic bond changes to a metallic bond.
  68. 68. QuestionsAn alloy is what type of substance?A.heterogeneous mixtureB.compoundC.mixture of elementsD.element
  69. 69. QuestionsWhich is NOT true about metallic solids?A.Metals are shiny.B.Metals are good conductors of heat and electricity.C.Metals are ductile.D.Metals have relatively low boiling points.
  70. 70. QuestionsElectrons in an atom’s outer most energy level are referred to as what?A.ionsB.cationsC.valence electronsD.noble-gas electrons
  71. 71. QuestionsWhat is the oxidation state of copper in Cu(II)Cl2?A.1+B.2+C.2–D.unable to determine
  72. 72. QuestionsWhich elements naturally occur with a full octet of valence electrons?A.alkali metalsB.alkali earth metalsC.halogensD.noble gases
  73. 73. QuestionsHow many electrons are in a full octet?A.10B.8C.6D.4
  74. 74. The End