1. Philip Dutton University of Windsor, Canada N9B 3P4 Prentice-Hall © 2002 General Chemistry Principles and Modern Applications Petrucci Harwood Herring 8 th Edition Chapter 12: Chemical Bonding II: Additional Aspects

2. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 2 of 47 Contents 12-1What a Bonding Theory Should Do 12-2Introduction to the Valence-Bond Method 12-3Hybridization of Atomic Orbitals 12-4Multiple Covalent Bonds 12-5Molecular Orbital Theory 12-6Delocalized Electrons: Bonding in the Benzene Molecule 12-7Bonding in Metals Focus on Photoelectron Spectroscopy

3. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 3 of 47 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.

4. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 4 of 47 Potential Energy Diagram

5. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 5 of 47 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.

6. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 6 of 47 Bonding in H 2 S

7. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 7 of 47 Example 12-1 Using the Valence-Bond Method to Describe a Molecular Structure. Describe the phosphine molecule, PH 3, by the valence-bond method.. Identify valence electrons:

8. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 8 of 47 Example 12-1 Sketch the orbitals: Overlap the orbitals: Describe the shape: Trigonal pyramidal

9. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 9 of 47 12-3 Hybridization of Atomic Orbitals

10. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 10 of 47 sp 3 Hybridization

11. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 11 of 47 sp 3 Hybridization

12. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 12 of 47 Bonding in Methane

13. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 13 of 47 sp 3 Hybridization in Nitrogen

14. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 14 of 47 Bonding in Nitrogen

15. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 15 of 47 sp 2 Hybridization

16. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 16 of 47 Orbitals in Boron

17. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 17 of 47 sp Hybridization

18. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 18 of 47 Orbitals in Beryllium

19. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 19 of 47 sp 3 d and sp 3 d 2 Hybridization

20. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 20 of 47 Hybrid Orbitals and VSEPR Write a plausible Lewis structure. Use VSEPR to predict electron geometry. Select the appropriate hybridization.

21. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 21 of 47 12-4 Multiple Covalent Bonds Ethylene has a double bond in its Lewis structure. VSEPR says trigonal planar at carbon.

22. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 22 of 47 Ethylene

23. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 23 of 47 Acetylene Acetylene, C 2 H 2, has a triple bond. VSEPR says linear at carbon.

24. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 24 of 47 12-5 Molecular Orbital Theory Atomic orbitals are isolated on atoms. Molecular orbitals span two or more atoms. LCAO –Linear combination of atomic orbitals. Ψ 1 = φ 1 + φ 2 Ψ 2 = φ 1 - φ 2

25. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 25 of 47 Combining Atomic Orbitals

26. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 26 of 47 Molecular Orbitals of Hydrogen

27. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 27 of 47 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 followed

28. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 28 of 47 Bond Order Stable species have more electrons in bonding orbitals than antibonding. Bond Order = No. e - in bonding MOs - No. e- in antibonding MOs 2

29. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 29 of 47 Diatomic Molecules of the First-Period BO = (1-0)/2 = ½ H2+H2+ BO = (2-0)/2 = 1 H2+H2+ BO = (2-1)/2 = ½ He 2 + BO = (2-2)/2 = 0 He 2 + BO = (e - bond - e - antibond )/2

30. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 30 of 47 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).

31. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 31 of 47 Molecular Orbitals of the Second Period

32. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 32 of 47 Combining p orbitals

33. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 33 of 47 Expected MO Diagram of C 2 Prentice-Hall © 2002 General Chemistry: Chapter 12 Slide

34. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 34 of 47 Modified MO Diagram of C 2

35. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 35 of 47 Prentice-Hall © 2002 General Chemistry: Chapter 12 MO Diagrams of 2 nd Period Diatomics

36. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 36 of 47 MO Diagrams of Heteronuclear Diatomics

37. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 37 of 47 12-6 Delocalized Electrons

38. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 38 of 47 Benzene

39. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 39 of 47 Benzene

40. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 40 of 47 Ozone

41. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 41 of 47 12-7 Bonding in Metals Electron sea model –Nuclei in a sea of e -. –Metallic lustre. –Malleability. Force applied

42. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 42 of 47 Bonding in Metals Band 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.

43. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 43 of 47 Band Theory

44. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 44 of 47 Semiconductors

45. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 45 of 47 Photovoltaic Cells

46. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 46 of 47 Focus on Photoelectron Spectroscopy

47. Prentice-Hall © 2002General Chemistry: Chapter 12Slide 47 of 47 Chapter 12 Questions 1, 3, 8, 10, 16, 29, 33, 39, 45, 59, 68, 72, 76