Chapter 10

1. Chapter 10 Bonding and Molecular Structure: Orbital Hybridization and Molecular Orbitals

2. Goals Understand the differences between valence bond theory and molecular orbital theory. Identify the hybridization of an atom in a molecule or ion. Understand the differences between bonding and antibonding molecular orbitals. Write the molecular orbital configuration for simple diatomic molecules.

3. Orbitals and Bonding Theories VSEPR Theory only explains molecular shapes. It says nothing about bonding in molecules In Valence Bond (VB) Theory (Linus Pauling) atoms share electron pairs by allowing their atomic orbitals to overlap. Another approach to rationalize chemical bonding is the Molecular Orbital (MO) Theory (Robert Mulliken): molecular orbitals are spread out or “delocalized” over the molecule.

4. Valence Bond (VB) Theory Covalent bonds are formed by theoverlapof atomic orbitals. Atomic orbitals on the central atom can mix and exchange their character with other atoms in a molecule. Process is calledhybridization. Hybrids are common: Pink flowers Mules Hybrid Orbitals have the same shapes as predicted by VSEPR.

5. 1s 1s + H H  bond

6. 1s 1s + H H E 1s H  bond

7. + H H H E 1s H  bond

8. 2p 2p + F F  bond F2

9. 2p E 2s 1s F

10. F 2p E 2s 1s F

11. Methane CH4 2p E 2s 1s C

12. Methane CH4 H H 2p E 2s 1s C

13. Methane CH4 H H H+ 2p E 2s 1s C

14. Methane CH4 H H– H H+ 2p E 2s 1s C

15. Z Y X Methane CH4 H H– H H+ 2p H E 90° 2s H C H 90° H 1s The approach is not correct, because… C

16. Methane CH4 H 109.5° C H H H Tetrahedral Geometry 4 Identical Bonds

17. Problem and Solution C must have 4 identical orbitals in valence shell for bonding solution: hybridization (theoretical mixing of the four atomic orbitals of carbon atom, the 2s and the three 2p)

18. Methane CH4 2p E 2s 1s

19. Methane CH4 2s 2p 2p E E 2s 1s 1s

20. Methane CH4 2s 2p 2p E E 2s 1s 1s

21. Methane CH4 2s 2p 2p E E 2s 1s 1s

22. Methane CH4 2p four sp3 orbitals E E 2s 1s 1s

23. + + – + 2p 2s

24. + + – + three 2p 2s = four sp3 hybrid orbitals

25. 4 identical sp3 hybrid orbitals: they are four because there was the combination of one s and three p atomic orbitals (25% s, 75% p) tetrahedral geometry

26. Methane CH4 H H H H 2p sp3 E E 2s 1s 1s

27. Valence Bond (VB) Theory

28. Predict the Hybridization of the Central Atom in aluminum bromide     Br   Electron-pair shape trigonal planar 3 regions Al     Br Br         Hybridization: sp2

29. 1s2s2p B   Trigonal Planar Electronic Geometry, sp2 1s2s2p2p B    1ssp2 hybrid     Electronic Structures: BF3 2s2p F [He] 

30. Trigonal Planar Electronic Geometry, sp2 BF3

31. Predict the Hybridization of the Central Atom in carbon dioxide CO2     C O O     2 regions Electron-pair shape, linear Hybridization: sp (50% s, 50% p)

32. 1s2s2p Be  1ssp hybrid     Linear Electronic Geometry, sp Electronic Structures: BeCl2 3s3p Cl [Ne] 

33. Predict the Hybridization of the Central Atom in Beryllium Chloride Two regions: electron-pair shape sp hybridization

34. Predict the Hybridization of the Central Atom in PF5 Five regions: Trigonal Bipyramidal Electronic Geometry sp3d hybridization, five sp3d hybrid orbitals

35. Predict the Hybridization of the Central Atom in xenon tetrafluoride

36. Predict the Hybridization of the Central Atom in xenon tetrafluoride       F F     6 regions electron-pair shape octahedral     Xe         F F      

37. Predict the Hybridization of the Central Atom in xenon tetrafluoride       F F     6 regions electron-pair shape octahedral     Xe         F F       sp3d2 hybridization

38. Predict the Hybridization of the Central Atom in SF6 Six regions: Octahedral Electronic Geometry - sp3d2 hybridization, six sp3d2 hybrid orbitals

39. Consider Ethylene, C2H4

40. Consider Ethylene, C2H4 H H C C H H

41. Consider Ethylene, C2H4 H H C C H H 3 regions trigonal planar

42. Consider Ethylene, C2H4 H H C C H H 3 regions trigonal planar sp2 hybridization

43. Consider Ethylene, C2H4 H H C C H H 3 regions trigonal planar sp2 hybridization

44. 2p E 2s 1s

45. 2s 2p 2p E E 2s 1s 1s

46. 2p 2p sp2 E E 2s 1s 1s

47. sp2 2p sp2 sp2

48. 2p sp2 sp2 sp2