1. Copyright © Houghton Mifflin Company. All rights reserved. 14a–1 The Central Themes of VB Theory Basic Principle A covalent bond forms when the orbitals of two atoms overlap and are occupied by a pair of electrons that have the highest probability of being located between the nuclei. Themes These overlapping orbitals can have up to two electrons that must have opposite spins (Pauli principle). The valence orbitals in a molecule are different from those in isolated atoms.

2. Copyright © Houghton Mifflin Company. All rights reserved. 14a–2 Figure 12.18: Three representations of the hydrogen 1s

3. Copyright © Houghton Mifflin Company. All rights reserved. 14a–3 Figure 12.19b: Representation of the 2p orbitals.

4. Copyright © Houghton Mifflin Company. All rights reserved. 14a–4 Figure 13.1: (a) The interaction of two hydrogen atoms (b) Energy profile as a function of the distance between the nuclei of the hydrogen atoms.

5. Copyright © Houghton Mifflin Company. All rights reserved. 14a–5 Figure 13.1: (a) The interaction of two hydrogen atoms (b) Energy profile as a function of the distance between the nuclei of the hydrogen atoms.

6. Copyright © Houghton Mifflin Company. All rights reserved. 14a–6 Hydrogen, H 2 Hydrogen fluoride, HFFluorine, F 2

7. Copyright © Houghton Mifflin Company. All rights reserved. 14a–7 Figure 14.1: (a) Lewis structure of the methane molecule (b) the tetrahedral molecular geometry of the methane molecule.

8. Copyright © Houghton Mifflin Company. All rights reserved. 14a–8 Figure 14.2: valence orbitals on a free carbon atom

9. Copyright © Houghton Mifflin Company. All rights reserved. 14a–9 Figure 14.1: (a) Lewis structure of the methane molecule (b) the tetrahedral molecular geometry of the methane molecule.

10. Copyright © Houghton Mifflin Company. All rights reserved. 14a–10 Figure 14.3: native 2s and three 2p atomic orbitals characteristic of a free carbon atome are combined to form a new set of four sp3 orbitals.

11. Copyright © Houghton Mifflin Company. All rights reserved. 14a–11 s pxpx pypy pzpz Carbon 1s 2 2s 2 2p 2 Carbon could only make two bonds if no hybridization occurs. However, carbon can make four equivalent bonds. sp 3 hybrid orbitals Energy sp 3 C atom of CH 4 orbital diagram B A B B B Brown, LeMay, Bursten, Chemistry The Central Science, 2000, page 321

12. Copyright © Houghton Mifflin Company. All rights reserved. 14a–12 Figure 14.4: Cross section of an sp3 orbital

13. Copyright © Houghton Mifflin Company. All rights reserved. 14a–13 The four sp 3 hybrid orbitals in CH 4 Promotion

14. Copyright © Houghton Mifflin Company. All rights reserved. 14a–14 Figure 11.9 The  bonds in ethane. both C are sp 3 hybridized s-sp 3 overlaps to  bonds sp 3 -sp 3 overlap to form a  bond relatively even distribution of electron density over all  bonds  (Greek sigma) bonds have axial symmetry and good overlap Rotation about C-C bond allowed.

15. Copyright © Houghton Mifflin Company. All rights reserved. 14a–15 Figure 14.6: Tetrahedral set of four sp 3 orbitals on the carbon atom

16. Copyright © Houghton Mifflin Company. All rights reserved. 14a–16 Figure 14.7: The nitrogen atom in ammonia is sp 3 hybridized.

17. Copyright © Houghton Mifflin Company. All rights reserved. 14a–17 The four sp 3 hybrid orbitals in CH 4 Promotion

18. Copyright © Houghton Mifflin Company. All rights reserved. 14a–18 The four sp 3 hybrid orbitals in CH 4 Promotion

19. Copyright © Houghton Mifflin Company. All rights reserved. 14a–19 The four sp 3 hybrid orbitals in NH 3 Promotion N N

20. Copyright © Houghton Mifflin Company. All rights reserved. 14a–20 The four sp 3 hybrid orbitals in NH 3 Promotion N

21. Copyright © Houghton Mifflin Company. All rights reserved. 14a–21 sp 3 hybridization of a carbon atom

22. Copyright © Houghton Mifflin Company. All rights reserved. 14a–22 sp 3 hybridization of a nitrogen atom 3 tetrahedral bonds with 1 lone pair sp 3

23. Copyright © Houghton Mifflin Company. All rights reserved. 14a–23 sp 3 hybridization of a nitrogen atom N

24. Copyright © Houghton Mifflin Company. All rights reserved. 14a–24 Figure 11.5 The sp 3 hybrid orbitals in H 2 O Lone pairs

25. Copyright © Houghton Mifflin Company. All rights reserved. 14a–25 Diamond - sp 3 hybridized C

26. Copyright © Houghton Mifflin Company. All rights reserved. 14a–26 Figure 14.8: The hybridization of the s, p x, and p y atomic orbitals results in the formation of three sp 2 orbitals centered in the xy plane. NB: The remaining p orbital can be empty or serve another function

27. Copyright © Houghton Mifflin Company. All rights reserved. 14a–27 The three sp 2 hybrid orbitals in BF 3 Promotion Region of overlap Note the single left over Unhybridized p orbital on B

28. Copyright © Houghton Mifflin Company. All rights reserved. 14a–28 Hybrid Orbitals 2s2s2p2p Ground-state B atom s pxpx pypy pzpz Energy sp 2 2p2p B atom of BH 3 orbital diagram hybridize s orbital 2s2s2p2p B atom with one electron “promoted” sp 2 hybrid orbitals p orbitals sp 2 hybrid orbitals shown together (large lobes only) three sp s hybrid orbitals H H H B

29. Copyright © Houghton Mifflin Company. All rights reserved. 14a–29 Figure 14.10: When one s and two p oribitals are mixed to form a set of three sp 2 orbitals, one p orbital remains unchanged and is perpendicular to the plane of the hybrid orbitals.

30. Copyright © Houghton Mifflin Company. All rights reserved. 14a–30 Figure 14.13: (a) The orbitals used to form the bonds in ethylene. (b) The Lewis structure for ethylene.

31. Copyright © Houghton Mifflin Company. All rights reserved. 14a–31

32. Copyright © Houghton Mifflin Company. All rights reserved. 14a–32 The plastics shown here were manufactured with ethylene. Source: Comstock - Mountainside, NJ

33. Copyright © Houghton Mifflin Company. All rights reserved. 14a–33 Figure 14.11: The s bonds in ethylene.

34. Copyright © Houghton Mifflin Company. All rights reserved. 14a–34 Figure 14.12: A carbon-carbon double bond consists of a s bond and a p bond.

35. Copyright © Houghton Mifflin Company. All rights reserved. 14a–35 Figure 14.48: The benzene molecule consists of a ring of six carbon atoms with one hydrogen atom bound to each carbon; all atoms are in the same plane. Sp2 hybridized

36. Copyright © Houghton Mifflin Company. All rights reserved. 14a–36 Graphite – sp 2 hybridized C

37. Copyright © Houghton Mifflin Company. All rights reserved. 14a–37 Fullerene-C 60 and Fullerene-C 70 What hybridization of C describes the structures?

38. Copyright © Houghton Mifflin Company. All rights reserved. 14a–38 Figure 14.14: When one s orbital and one p orbital are hybridized, a set of two sp orbitals oriented at 180 degrees results.

39. Copyright © Houghton Mifflin Company. All rights reserved. 14a–39 Figure 14.18: Orbital arrangement for an sp 2 hybridized oxygen atom

40. Copyright © Houghton Mifflin Company. All rights reserved. 14a–40 Figure 14.19: (a) Orbitals predicted by the LE model to describe (b) The Lewis structure for carbon dioxide

41. Copyright © Houghton Mifflin Company. All rights reserved. 14a–41 Figure 14.17: Orbitals of an sp hybridized carbon atom

42. Copyright © Houghton Mifflin Company. All rights reserved. 14a–42 Figure 14.15: The hybrid orbitals in the CO 2 molecule

43. Copyright © Houghton Mifflin Company. All rights reserved. 14a–43 Figure 14.20: (a) An sp hybridized nitrogen atom (b) The s bond in the N 2 molecule (c) the two p bonds in N 2 are formed

44. Copyright © Houghton Mifflin Company. All rights reserved. 14a–44 Figure 14.16: orbital energy level diagram for the formation of sp hybrid orbitals of carbon.

45. Copyright © Houghton Mifflin Company. All rights reserved. 14a–45 Hybrid Orbitals spsp 2 sp 3 sp 3 dsp 3 d 2 Types of Hybrid Orbitals Shapes: linear triangular tetrahedral trig. bipyram. Octahedral # orbitals: 2 3 4 5 6

46. Copyright © Houghton Mifflin Company. All rights reserved. 14a–46 The conceptual steps from molecular formula to the hybrid orbitals used in bonding. Molecular formula Lewis structure Molecular shape and e - group arrangement Hybrid orbitals Step 1Step 2Step 3

47. Copyright © Houghton Mifflin Company. All rights reserved. 14a–47 Figure 14.24: The relationship among the number of effective pairs, their spatial arrangement, and the hybrid orbital set required

48. Copyright © Houghton Mifflin Company. All rights reserved. 14a–48 Figure 13.1: (a) The interaction of two hydrogen atoms (b) Energy profile as a function of the distance between the nuclei of the hydrogen atoms.

49. Copyright © Houghton Mifflin Company. All rights reserved. 14a–49 Figure 13.1: (a) The interaction of two hydrogen atoms (b) Energy profile as a function of the distance between the nuclei of the hydrogen atoms.

50. Copyright © Houghton Mifflin Company. All rights reserved. 14a–50 Figure 14.25: The combination of hydrogen 1s atomic orbitals to form MOs

51. Copyright © Houghton Mifflin Company. All rights reserved. 14a–51 Figure 14.25: The combination of hydrogen 1s atomic orbitals to form MOs

52. Copyright © Houghton Mifflin Company. All rights reserved. 14a–52 10.6

53. Copyright © Houghton Mifflin Company. All rights reserved. 14a–53 Auto mufflers use destructive interference of sound waves to reduce engine noises.  -  ( - sign flips phase of the sound wave function)  -  = 0

54. Copyright © Houghton Mifflin Company. All rights reserved. 14a–54 Bose is $200. Want to do it yourself? See Web site. http://www.headwize.com/projects/noise_prj.htm

55. Copyright © Houghton Mifflin Company. All rights reserved. 14a–55

56. Copyright © Houghton Mifflin Company. All rights reserved. 14a–56 Amplitudes of wave functions added An analogy between light waves and atomic wave functions. Amplitudes of wave functions subtracted. NOTE: +/- signs show PHASES of waves, NOT CHARGES!

57. Copyright © Houghton Mifflin Company. All rights reserved. 14a–57 Figure 14.26: (a) The MO energy-level diagram for the H2 molecule (b) The shapes of the Mos are obtained by squaring the wave functions for MO1 and MO2.

58. Copyright © Houghton Mifflin Company. All rights reserved. 14a–58 Figure 14.27: Bonding and anitbonding MOs

59. Copyright © Houghton Mifflin Company. All rights reserved. 14a–59 Figure 14.30: The MO energy-level diagram for the He 2 + ion. # BONDING e’s = 2 # ANTIBONDING e’s = 1 Bond order = ½(2-1) = ½

60. Copyright © Houghton Mifflin Company. All rights reserved. 14a–60 Figure 14.31: The MO energy-level diagram for the H 2 + ion

61. Copyright © Houghton Mifflin Company. All rights reserved. 14a–61 Figure 14.28: MO energy-level diagram for the H 2 molecule

62. Copyright © Houghton Mifflin Company. All rights reserved. 14a–62 Figure 14.29: The MO energy-level diagram for the He 2 molecule

63. Copyright © Houghton Mifflin Company. All rights reserved. 14a–63 Figure 14.30: The MO energy-level diagram for the He 2 + ion.

64. Copyright © Houghton Mifflin Company. All rights reserved. 14a–64 Figure 14.31: The MO energy-level diagram for the H 2 + ion

65. Copyright © Houghton Mifflin Company. All rights reserved. 14a–65 Figure 14.32: The MO energy-level diagram for the H 2 - ion

66. Copyright © Houghton Mifflin Company. All rights reserved. 14a–66

67. Copyright © Houghton Mifflin Company. All rights reserved. 14a–67 Figure 14.33: The relative sizes of the lithium 1s and 2s atomic orbitals

68. Copyright © Houghton Mifflin Company. All rights reserved. 14a–68 Figure 14.34: The MO energy-level diagram for the Li 2 molecule

69. Copyright © Houghton Mifflin Company. All rights reserved. 14a–69 Figure 14.35: The three mutually perpendicular 2p orbitals on tow adjacent boron atoms.

70. Copyright © Houghton Mifflin Company. All rights reserved. 14a–70 Figure 14.36: The two p oribitals on the boron atom that overlap head-on combine to form bonding and antibonding orbitals.

71. Copyright © Houghton Mifflin Company. All rights reserved. 14a–71 Figure 14.37: The expected MO energy-level diagram for the combustion of the 2 P orbitals on two boron atoms.

72. Copyright © Houghton Mifflin Company. All rights reserved. 14a–72 Figure 14.37: The expected MO energy-level diagram for the combustion of the 2 P orbitals on two boron atoms.

73. Copyright © Houghton Mifflin Company. All rights reserved. 14a–73 Figure 14.38: The expected MO energy-level diagram for the B 2 molecule

74. Copyright © Houghton Mifflin Company. All rights reserved. 14a–74 Figure 14.39: An apparatus used to measure the paramagnetism of a sample

75. Copyright © Houghton Mifflin Company. All rights reserved. 14a–75 Figure 14.40: The correct MO energy-level diagram for the B 2 molecule.

76. Copyright © Houghton Mifflin Company. All rights reserved. 14a–76 Figure 14.41: The MO energy-level diagrams, bond orders, bond energies, and bond lengths for the diatomic molecules, B 2 through F 2.

77. Copyright © Houghton Mifflin Company. All rights reserved. 14a–77 Figure 14.42: When liquid oxygen is poured into the space between the poles of a strong magnet, it remains there until it boils away. Source: Donald Clegg

78. Copyright © Houghton Mifflin Company. All rights reserved. 14a–78 Figure 14.48: The benzene molecule consists of a ring of six carbon atoms with one hydrogen atom bound to each carbon; all atoms are in the same plane.

79. Copyright © Houghton Mifflin Company. All rights reserved. 14a–79 Figure 14.49: The s bonding system in the benzene molecule

80. Copyright © Houghton Mifflin Company. All rights reserved. 14a–80 Figure 14.50: The MO system in benzene is formed by combining the six p orbitals

81. Copyright © Houghton Mifflin Company. All rights reserved. 14a–81 Figure 14.47: The resonance structures for O 3 and NO 3 -

82. Copyright © Houghton Mifflin Company. All rights reserved. 14a–82 Figure 14.51: The p orbitals used to form the bonding system in the NO 3 - ion

83. Copyright © Houghton Mifflin Company. All rights reserved. 14a–83 Figure 14.55: The molecular orbital diagram for the ground state of NO +

84. Copyright © Houghton Mifflin Company. All rights reserved. 14a–84 Electromagnetic spectrum λ ν

85. Copyright © Houghton Mifflin Company. All rights reserved. 14a–85 Figure 14.52: Schematic representation of two electronic energy levels in a molecule

86. Copyright © Houghton Mifflin Company. All rights reserved. 14a–86 Figure 14.53: The various types of transitions are shown by vertical arrows.

87. Copyright © Houghton Mifflin Company. All rights reserved. 14a–87 Figure 14.54: Spectrum corresponding to the changes indicated in Fig. 14.53.

88. Copyright © Houghton Mifflin Company. All rights reserved. 14a–88 The molecular structure of beta-carotene

89. Copyright © Houghton Mifflin Company. All rights reserved. 14a–89 Figure 14.57: The electronic absorption spectrum of beta-carotene.

90. VIBRATIONS

92. Copyright © Houghton Mifflin Company. All rights reserved. 14a–92 Figure 14.58: The potential curve for a diatomic molecule

93. Copyright © Houghton Mifflin Company. All rights reserved. 14a–93 Figure 14.59: Morse energy curve for a diatomic molecule.

94. Copyright © Houghton Mifflin Company. All rights reserved. 14a–94 Figure 14.60: The three fundamental vibrations for sulfur dioxide

95. Copyright © Houghton Mifflin Company. All rights reserved. 14a–95 Figure 14.61: The infrared spectrum of CH 2 Cl 2.

96. Copyright © Houghton Mifflin Company. All rights reserved. 14a–96

97. Copyright © Houghton Mifflin Company. All rights reserved. 14a–97

98. Copyright © Houghton Mifflin Company. All rights reserved. 14a–98 Figure 14.62: Representations of the two spin states of the proton interacting

99. Copyright © Houghton Mifflin Company. All rights reserved. 14a–99 Figure 14.63: The molecular structure of bromoethane

100. Copyright © Houghton Mifflin Company. All rights reserved. 14a–100 Figure 14.64: The expected NMR spectrum for bromoethane

101. Copyright © Houghton Mifflin Company. All rights reserved. 14a–101 Figure 14.65: The spin of proton H y can by "up" or "down"

102. Copyright © Houghton Mifflin Company. All rights reserved. 14a–102 Figure 14.66: The spins for protons H y can be "up", can be opposed (in 2 ways) or can both be "down"

103. Copyright © Houghton Mifflin Company. All rights reserved. 14a–103 Figure 14.67: The spins for the protons H y can by arranged as shown in (a) leading to four different magnetic environments

104. Copyright © Houghton Mifflin Company. All rights reserved. 14a–104 Figure 14.68: The NMR spectrum of CH 3 CH 2 B r (bromoethane) with TMS reference

105. Copyright © Houghton Mifflin Company. All rights reserved. 14a–105 Figure 14.69: The molecule (2-butanone)

106. Copyright © Houghton Mifflin Company. All rights reserved. 14a–106 Fullerene-C 60 and Fullerene-C 70

107. Copyright © Houghton Mifflin Company. All rights reserved. 14a–107 Fullerene-C 60 and Fullerene-C 70

108. Copyright © Houghton Mifflin Company. All rights reserved. 14a–108 Figure 14.70: A technician speaks to a patient before heis moved intot eh cavity of a magnetic resonance imaging (MRI) machine.

109. Copyright © Houghton Mifflin Company. All rights reserved. 14a–109 Figure 14.71: A colored Magnetic Resonance Imaging (MRI) scan through a human head, showing a healthy brain in side view.