Ch12

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Ch12

  1. 1. General ChemistryPrinciples and Modern Applications Petrucci • Harwood • Herring 8th Edition Chapter 12: Chemical Bonding II: Additional Aspects Philip Dutton University of Windsor, Canada N9B 3P4 Prentice-Hall © 2002
  2. 2. Contents 12-1 What a Bonding Theory Should Do 12-2 Introduction to the Valence-Bond Method 12-3 Hybridization of Atomic Orbitals 12-4 Multiple Covalent Bonds 12-5 Molecular Orbital Theory 12-6 Delocalized Electrons: Bonding in the Benzene Molecule 12-7 Bonding in Metals Focus on Photoelectron SpectroscopyPrentice-Hall General Chemistry: ChapterSlide 2 of 47 12
  3. 3. 12-1 What a Bonding Theory Should Do • Bring atoms together from a distance. – e- are attracted to both nuclei. – e- are repelled by each other. – Nuclei are repelled by each other. • Plot the total potential energy verses distance. – -ve energies correspond to net attractive forces. – +ve energies correspond to net repulsive forces.Prentice-Hall General Chemistry: ChapterSlide 3 of 47 12
  4. 4. Potential Energy DiagramPrentice-Hall General Chemistry: ChapterSlide 4 of 47 12
  5. 5. 12-2 Introduction to the Valence-Bond Method• Atomic orbital overlap describes covalent bonding.• Area of overlap of orbitals is in phase.• A localized model of bonding.Prentice-Hall General Chemistry: ChapterSlide 5 of 47 12
  6. 6. Bonding in H2SPrentice-Hall General Chemistry: ChapterSlide 6 of 47 12
  7. 7. Example 12-1Using the Valence-Bond Method to Describe a MolecularStructure.Describe the phosphine molecule, PH3, by the valence-bondmethod..Identify valence electrons: Prentice-Hall General Chemistry: ChapterSlide 7 of 47 12
  8. 8. Example 12-1Sketch the orbitals:Overlap the orbitals:Describe the shape: Trigonal pyramidal Prentice-Hall General Chemistry: ChapterSlide 8 of 47 12
  9. 9. 12-3 Hybridization of Atomic OrbitalsPrentice-Hall General Chemistry: ChapterSlide 9 of 47 12
  10. 10. sp3 HybridizationPrentice-Hall General Chemistry: ChapterSlide 10 of 47 12
  11. 11. sp3 HybridizationPrentice-Hall General Chemistry: ChapterSlide 11 of 47 12
  12. 12. Bonding in MethanePrentice-Hall General Chemistry: ChapterSlide 12 of 47 12
  13. 13. sp3 Hybridization in NitrogenPrentice-Hall General Chemistry: ChapterSlide 13 of 47 12
  14. 14. Bonding in NitrogenPrentice-Hall General Chemistry: ChapterSlide 14 of 47 12
  15. 15. sp2 HybridizationPrentice-Hall General Chemistry: ChapterSlide 15 of 47 12
  16. 16. Orbitals in BoronPrentice-Hall General Chemistry: ChapterSlide 16 of 47 12
  17. 17. sp HybridizationPrentice-Hall General Chemistry: ChapterSlide 17 of 47 12
  18. 18. Orbitals in BerylliumPrentice-Hall General Chemistry: ChapterSlide 18 of 47 12
  19. 19. sp3d and sp3d2 HybridizationPrentice-Hall General Chemistry: ChapterSlide 19 of 47 12
  20. 20. Hybrid Orbitals and VSEPR• Write a plausible Lewis structure.• Use VSEPR to predict electron geometry.• Select the appropriate hybridization.Prentice-Hall General Chemistry: ChapterSlide 20 of 47 12
  21. 21. 12-4 Multiple Covalent Bonds• Ethylene has a double bond in its Lewis structure.• VSEPR says trigonal planar at carbon.Prentice-Hall General Chemistry: ChapterSlide 21 of 47 12
  22. 22. EthylenePrentice-Hall General Chemistry: ChapterSlide 22 of 47 12
  23. 23. Acetylene• Acetylene, C2H2, has a triple bond.• VSEPR says linear at carbon.Prentice-Hall General Chemistry: ChapterSlide 23 of 47 12
  24. 24. 12-5 Molecular Orbital Theory • Atomic orbitals are isolated on atoms. • Molecular orbitals span two or more atoms. • LCAO – Linear combination of atomic orbitals. Ψ1 = φ1 + φ2 Ψ2 = φ1 - φ2Prentice-Hall General Chemistry: ChapterSlide 24 of 47 12
  25. 25. Combining Atomic OrbitalsPrentice-Hall General Chemistry: ChapterSlide 25 of 47 12
  26. 26. Molecular Orbitals of HydrogenPrentice-Hall General Chemistry: ChapterSlide 26 of 47 12
  27. 27. Basic Ideas Concerning MOs• Number of MOs = Number of AOs.• Bonding and antibonding MOs formed from AOs.• e- fill the lowest energy MO first.• Pauli exclusion principle is followed.• Hund’s rule is followedPrentice-Hall General Chemistry: ChapterSlide 27 of 47 12
  28. 28. Bond Order • Stable species have more electrons in bonding orbitals than antibonding. No. e- in bonding MOs - No. e- in antibonding MOsBond Order = 2 Prentice-Hall General Chemistry: ChapterSlide 28 of 47 12
  29. 29. Diatomic Molecules of the First-Period BO = (e-bond - e-antibond )/2 BOH += (1-0)/2 = ½ 2 BOH += (2-0)/2 = 1 2 BOHe + = (2-1)/2 = ½ 2 BOHe + = (2-2)/2 = 0 2Prentice-Hall General Chemistry: ChapterSlide 29 of 47 12
  30. 30. Molecular Orbitals of the Second Period• First period use only 1s orbitals.• Second period have 2s and 2p orbitals available.• p orbital overlap: – End-on overlap is best – sigma bond (σ). – Side-on overlap is good – pi bond (π).Prentice-Hall General Chemistry: ChapterSlide 30 of 47 12
  31. 31. Molecular Orbitals of the Second PeriodPrentice-Hall General Chemistry: ChapterSlide 31 of 47 12
  32. 32. Combining p orbitalsPrentice-Hall General Chemistry: ChapterSlide 32 of 47 12
  33. 33. Expected MO Diagram of C2Prentice-Hall © 2002 General Chemistry: Chapter 12Prentice-Hall 12 Slide General Chemistry: ChapterSlide 33 of 47
  34. 34. Modified MO Diagram of C2Prentice-Hall General Chemistry: ChapterSlide 34 of 47 12
  35. 35. MO Diagrams of 2nd Period DiatomicsPrentice-Hall © 2002 General Chemistry: Chapter 12Prentice-Hall General Chemistry: ChapterSlide 35 of 47 12
  36. 36. MO Diagrams of Heteronuclear Diatomics Prentice-Hall General Chemistry: ChapterSlide 36 of 47 12
  37. 37. 12-6 Delocalized ElectronsPrentice-Hall General Chemistry: ChapterSlide 37 of 47 12
  38. 38. BenzenePrentice-Hall General Chemistry: ChapterSlide 38 of 47 12
  39. 39. BenzenePrentice-Hall General Chemistry: ChapterSlide 39 of 47 12
  40. 40. OzonePrentice-Hall General Chemistry: ChapterSlide 40 of 47 12
  41. 41. 12-7 Bonding in Metals • Electron sea model – Nuclei in a sea of e-. – Metallic lustre. – Malleability. Force appliedPrentice-Hall General Chemistry: ChapterSlide 41 of 47 12
  42. 42. Bonding in MetalsBand theory.• Extension of MO theory. N atoms give N orbitals that are closely spaced in energy. • N/2 are filled. The valence band. • N/2 are empty. The conduction band. Prentice-Hall General Chemistry: ChapterSlide 42 of 47 12
  43. 43. Band TheoryPrentice-Hall General Chemistry: ChapterSlide 43 of 47 12
  44. 44. SemiconductorsPrentice-Hall General Chemistry: ChapterSlide 44 of 47 12
  45. 45. Photovoltaic CellsPrentice-Hall General Chemistry: ChapterSlide 45 of 47 12
  46. 46. Focus on Photoelectron SpectroscopyPrentice-Hall General Chemistry: ChapterSlide 46 of 47 12
  47. 47. Chapter 12 Questions 1, 3, 8, 10, 16, 29, 33, 39, 45, 59, 68, 72, 76Prentice-Hall General Chemistry: ChapterSlide 47 of 47 12

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