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Chapter 9 Even Problems
24. For each of the following molecules or ions that contain sulfur, write the Lewis structure,
predict the molecular structure, and give the expected hybrid orbitals for sulfur.
bent, sp2
a. SO2
f. SO42–
tetrahedral, sp3
S
O
2–
O
O
O—S—O
O
trig. planar, sp2
b. SO3
bent, sp3
g. SF2
O
S
O
c. S2O32–
S
O
F
F
tetrahedral, sp3
see-saw, sp3d
h. SF4
2–
O
S—S—O
F
O
S
F
F
F
d. S2O82–
both tetrahedral, sp3
see-saw, sp3d; bent, sp3
i. F3S–SF
O
O
F
2–
F
O—S—O—O—S—O
O
e. SO32–
S
S—F
O
trig. pyramidal, sp3
O—S—O
O
2–
F
j. SF5+
trigonal bipyramidal, sp3d
+
F
F
F—S
F
F
28. Many important compounds in the chemical industry are derivatives of ethylene, C2H4. Two
of them are acrylonitrile (the first one) and methyl methacrylate.
H
H
H
C=C
H
C
H
N
sp2
sp2
CH3
C=C
sp2
sp
C–O–CH3
O
sp2
sp3
sp2
sp3
Complete the Lewis structures, showing all lone pairs. Give the hybridization of all carbon
atoms. In acrylonitrile, how many of the atoms in the molecule lie in the same plane? How
many  bonds and how many  bonds are there in each compound?
acrylonitrile: all atoms in the same plane; 6  bonds, 3  bonds
methyl methacrylate: 14  bonds, 2  bonds
32. The antibiotic thiarubin-A was discovered by studying the feeding habits of wild
chimpanzees in Tanzania. The structure for thiarubin-A is
H
H
C–C
H3C–C≡C–C
C–C≡C–C≡C–CH=CH2
S—S
a. Complete the Lewis structure showing all lone pairs of electrons.
b. Indicate the hybrid orbitals used by the carbon and sulfur atoms.
sp3–sp–sp–sp2
sp2–sp2
sp2–sp–sp–sp–sp–sp2–sp2
sp3–sp3
c. How many  and  bonds are present in this molecule?
23 , 9 
34. Which of the following are predicted by the molecular orbital model to be stable diatomic
species?
a. N22–, O22–, F22–
draw MO diagrams:
N22–
bond order = (6–2)/2 = 2
stable
O22–
bond order = (6–4)/2 = 1
stable
F22–
bond order = (6–6)/2 = 0
unstable
b. Be2, B2, Ne2
Be2
bond order = (2–2)/2 = 0
unstable
B2
bond order = (2–0)/2 = 1
stable
Ne2
bond order = (6–6)/2 = 0
unstable
40. Construct a molecular orbital energy-level diagram for the Cl2 molecule. Is Cl2 expected to
be paramagnetic?
___ 3p*
3p ↑↓_ ↑↓_ ↑__
↑↓_ ↑↓_ 3p*
↑↓_ ↑↓_↑_ 3p
↑↓_ ↑↓_ 3p
↑↓_3p
3s*
↑↓_ 3s
↑↓_3s
↑↓_
3s ↑↓_
bond order = (8–6)/2 = 1
diamagnetic
61. (challenge problem) Two structures can be drawn for cyanuric acid:
H
O
N
C
N
H
O
C
H
N
O–C
N
C
N
H
O
O–H
C
N
C
O
H
Complete the Lewis dot structures above (add lone pairs).
a. Are these two structures the same molecule? Explain.
They are both H3C3N3O3, but their atoms are connected differently: they are isomers.
b. Give the hybridization of the carbon and nitrogen atoms in each structure.
structure 1: carbons are sp2, nitrogens are sp3
structure 2: all carbons and nitrogens are sp2
c. Use bond energies to predict which form is more stable; that is, which contains the strongest
bonds?
structure 1: 3 (C=O) + 6 (C–N) + 3 (N–H)
3 (745 kJ) + 6 (305 kJ) + 3 (391 kJ) = 5238 kJ
structure 2: 3 (C–O) + 3 (C–N) + 3 (C=N) + 3 (O–H)
3 (358 kJ) + 3 (305 kJ) + 3 (615 kJ) + 3 (467 kJ) = 5235 kJ
Structure 1 has slightly stronger bonds, but the two structures are essentially comparable.