Chem I Chapter 8
Matching
Match each item with the correct statement below.
a. coordinate covalent bond
d. single covalent bond
b. double covalent bond
e. polar bond
c. structural formula
f. hydrogen bond
____
1. a depiction of the arrangement of atoms in molecules and polyatomic ions
____
2. a covalent bond in which only one pair of electrons is shared
____
3. a covalent bond in which two pairs of electrons are shared
____
4. a covalent bond in which the shared electron pair comes from only one of the atoms
____
5. a covalent bond between two atoms of significantly different electronegativities
____
6. a type of bond that is very important in determining the properties of water and of important biological
molecules such as proteins and DNA
Match each item with the correct statement below.
a. network solid
e. tetrahedral angle
b. bonding orbital
f. VSEPR theory
c. dipole interaction
g. sigma bond
d. bond dissociation energy
____
7. energy needed to break a single bond between two covalently bonded atoms
____
8. symmetrical bond along the axis between the two nuclei
____
9. molecular orbital that can be occupied by two electrons of a covalent bond
____ 10. 109.5
____ 11. shapes adjust so valence-electron pairs are as far apart as possible
____ 12. attraction between polar molecules
____ 13. crystal in which all the atoms are covalently bonded to each other
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____ 14. What information does a molecular formula provide?
a. the number and kind of atoms that are bonded by the transfer of electrons
b. the simplest whole-number ratio of atoms that are bonded by the transfer of electrons
c. information about a molecule’s structure
d. the number and kind of atoms present in a molecule
____ 15. What is shown by the structural formula of a molecule or polyatomic ion?
a. the arrangement of bonded atoms
b. the number of ionic bonds
c. the number of metallic bonds
d. the shapes of molecular orbitals
____ 16. The molecular formula for the compound hydrogen cyanide is HCN. What information does the molecular
formula provide about hydrogen cyanide?
a. The formula HCN indicates that a molecule of hydrogen cyanide contains one hydrogen
atom, one carbon atom, and one nitrogen atom.
b. The formula HCN shows that hydrogen cyanide could contain 2 atoms of each element;
hydrogen, carbon and nitrogen, as long as there is a one to one ratio.
c. The formula HCN shows that hydrogen cyanide has a single covalent bond between the
hydrogen and carbon atoms and a triple covalent bond between the carbon and nitrogen
atoms.
d. The formula HCN shows that hydrogen cyanide has a single ionic bond between the
hydrogen and carbon atoms and a triple ionic bond between the carbon and nitrogen
atoms.
____ 17. How do atoms achieve noble-gas electron configurations in single covalent bonds?
a. One atom completely loses two electrons to the other atom in the bond.
b. Two atoms share two pairs of electrons.
c. Two atoms share two electrons.
d. Two atoms share one electron.
____ 18. Why do atoms share electrons in covalent bonds?
a. to become ions and attract each other
b. to attain a noble-gas electron configuration
c. to become more polar
d. to increase their atomic numbers
____ 19. Which of the following elements can form diatomic molecules held together by triple covalent bonds?
a. carbon
b. oxygen
c. fluorine
d. nitrogen
____ 20. Which noble gas has the same electron configuration as the oxygen in a water molecule?
a. helium
b. neon
c. argon
d. xenon
____ 21. Which elements can form diatomic molecules joined by a single covalent bond?
a. hydrogen only
b. halogens only
c. halogens and members of the oxygen group only
d. hydrogen and the halogens only
____ 22. What is the representative unit in a molecular compound?
a. a molecule
b. an ion
c. a formula unit
d. shared electrons
____ 23. Which of the following electron configurations gives the correct arrangement of the four valence electrons of
the carbon atom in the molecule methane (CH )?
a. 2s 2p
b. 2s 2p 3s
c. 2s 2p 3s
d. 2s 2p
____ 24. Which of the following diatomic molecules is joined by a double covalent bond?
a.
b.
c.
d.
____ 25. Which molecule has a single covalent bond?
a. CO
b. Cl
c. CO
d. N
____ 26. The chemical formula of an ionic compound shows
a. how many atoms of each element a molecule contains.
b. the lowest whole-number ratio between ions in the ionic compound.
c. which molecules the ionic compound contains.
d. how the atoms bond.
____ 27. Once formed, how are coordinate covalent bonds different from other covalent bonds?
a. They are stronger.
b. They are more ionic in character.
c. They are weaker.
d. There is no difference.
____ 28. When H forms a bond with H O to form the hydronium ion H O , this bond is called a coordinate
covalent bond because
a. both bonding electrons come from the oxygen atom.
b. it forms an especially strong bond.
c. the electrons are equally shared.
d. the oxygen no longer has eight valence electrons.
____ 29. Which of the following bonds is the least reactive?
a. C—C
b. H—H
c. O—H
d. H—Cl
____ 30. How many valid electron dot formulas—having the same number of electron pairs for a molecule or ion—can
be written when a resonance structure occurs?
a. 0
b. 1 only
c. 2 only
d. 2 or more
____ 31. In which of the following compounds is the octet expanded to include 12 electrons?
a. H S
b. PCl
c. PCl
d. SF
____ 32. A resonance structure, like the one above, represents
a. a difference in energy.
b. electron pairs resonating back and forth between the extremes of the two structures.
c. a difference in bond length, one shorter than the other.
d. a hybrid of the extremes represented by the resonance forms.
____ 33. Molecular orbital theory is based upon which of the following models of the atom?
a. classical mechanical model
b. Bohr model
c. quantum mechanical model
d. Democritus’s model
____ 34. A bond that is not symmetrical along the axis between two atomic nuclei is a(n) ____.
a. alpha bond
b. sigma bond
c. pi bond
d. beta bond
____ 35. A pair of molecular orbitals is formed by the
a. splitting of a single atomic orbital.
b. reproduction of a single atomic orbital.
c. overlap of two atomic orbitals from the same atom.
d. overlap of two atomic orbitals from different atoms.
____ 36. The side-by-side overlap of p orbitals produces what kind of bond?
a. alpha bond
b. beta bond
c. pi bond
d. sigma bond
____ 37. Where are the electrons most probably located in a molecular bonding orbital?
a. anywhere in the orbital
b. between the two atomic nuclei
c. in stationary positions between the two atomic nuclei
d. in circular orbits around each nucleus
____ 38. Sigma bonds are formed as a result of the overlapping of which type(s) of atomic orbital(s)?
a. s only
b. p only
c. d only
d. s and p
____ 39. Which of the following bond types is normally the weakest?
a. sigma bond formed by the overlap of two s orbitals
b. sigma bond formed by the overlap of two p orbitals
c. sigma bond formed by the overlap of one s and one p orbital
d. pi bond formed by the overlap of two p orbitals
____ 40. According to VSEPR theory, molecules adjust their shapes to keep which of the following as far apart as
possible?
a. pairs of valence electrons
b. inner shell electrons
c. mobile electrons
d. the electrons closest to the nuclei
____ 41. The shape of the methane molecule is ____.
a. tetrahedral
b. square
c. four-cornered
d. planar
____ 42. What causes water molecules to have a bent shape, according to VSEPR theory?
a. repulsive forces between unshared pairs of electrons
b. interaction between the fixed orbitals of the unshared pairs of oxygen
c. ionic attraction and repulsion
d. the unusual location of the free electrons
____ 43. Which of the following theories provides information concerning both molecular shape and molecular
bonding?
a. molecular orbital theory
b. VSEPR theory
c. orbital hybridization theory
d. Bohr atomic theory
____ 44. Experimental evidence suggests that the H—C—H bond angles in ethene, C H , are ____.
a. 90
b. 109.5
c. 120
d. 180
____ 45. What type of hybrid orbital exists in the methane molecule?
a. sp
b. sp
c. sp
d. sp d
____ 46. What is the shape of a molecule with a triple bond?
a. tetrahedral
b. pyramidal
c. bent
d. linear
____ 47. What type of hybridization occurs in the orbitals of a carbon atom participating in a triple bond with another
carbon atom?
a.
b.
c.
d.
____ 48. How many pi bonds are formed when sp hybridization occurs in ethene, C H ?
a. 0
b. 1
c. 2
d. 3
____ 49. Which of the following atoms acquires the most negative charge in a covalent bond with hydrogen?
a. C
b. Na
c. O
d. S
____ 50. A bond formed between a silicon atom and an oxygen atom is likely to be ____.
a. ionic
b. coordinate covalent
c. polar covalent
d. nonpolar covalent
____ 51. Which of the following covalent bonds is the most polar?
a. H—F
b. H—C
c. H—H
d. H—N
____ 52. When placed between oppositely charged metal plates, the region of a water molecule attracted to the
negative plate is the ____.
a. hydrogen region of the molecule
b. geometric center of the molecule
c. H—O—H plane of the molecule
d. oxygen region of the molecule
____ 53. What is thought to cause the dispersion forces?
a. attraction between ions
b. motion of electrons
c. sharing of electron pairs
d. differences in electronegativity
____ 54. Which of the forces of molecular attraction is the weakest?
a. dipole interaction
b. dispersion
c. hydrogen bond
d. single covalent bond
____ 55. What causes dipole interactions?
a. sharing of electron pairs
b. attraction between polar molecules
c. bonding of a covalently bonded hydrogen to an unshared electron pair
d. attraction between ions
____ 56. What are the weakest attractions between molecules?
a. ionic forces
b. Van der Waals forces
c. covalent forces
d. hydrogen forces
____ 57. What causes hydrogen bonding?
a. attraction between ions
b. motion of electrons
c. sharing of electron pairs
d. bonding of a covalently bonded hydrogen atom with an unshared electron pair
____ 58. Why is hydrogen bonding only possible with hydrogen?
a. Hydrogen’s nucleus is electron deficient when it bonds with an electronegative atom.
b. Hydrogen is the only atom that is the same size as an oxygen atom.
c. Hydrogen is the most electronegative element.
d. Hydrogen tends to form covalent bonds.
____ 59. Which type of solid has the highest melting point?
a. ionic solid
b. network solid
c. metal
d. nonmetallic solid
____ 60. What is required in order to melt a network solid?
a. breaking Van der Waals bonds
b. breaking ionic bonds
c. breaking hydrogen bonds
d. breaking covalent bonds
Numeric Response
61. How many valence electrons does an iodine atom have?
62. What is the total number of covalent bonds normally associated with a single carbon atom in a compound?
63. How many electrons are shared in a single covalent bond?
64. How many electrons does a nitrogen atom need to gain in order to attain a noble-gas electron configuration?
65. How many unshared pairs of electrons does the nitrogen atom in ammonia possess?
66. How many electrons does carbon need to gain in order to obtain a noble-gas electron configuration?
67. How many electrons are shared in a double covalent bond?
68. How many covalent bonds are in a covalently bonded molecule containing 1 phosphorus atom and 3 chlorine
atoms?
69.
How many unshared pairs of electrons are in a molecule of hydrogen iodide?
70. What is the bond angle in a water molecule?
Essay
71. What is bond dissociation energy, and how does it affect carbon compounds?
72. Can some atoms exceed the limits of the octet rule in bonding? If so, give an example.
73. Indicate how bonding is explained in terms of molecular orbitals.
74. Explain a pi bond and a sigma bond. Which of these bond types tends to be the weaker? Why?
75. Explain what is meant by VSEPR theory. Give an example of how VSEPR theory can be applied to predict
the shape of a molecule.
76. Explain what is meant by orbital hybridization. Give an example of a molecule in which orbital hybridization
occurs.
77. Choose a molecule which displays an exception to the octet rule and illustrate clearly, using Lewis dot
structures, why it is considered an exception. Discuss whether resonance structures can account for its
stability.
78. What determines the degree of polarity in a bond? Distinguish between nonpolar covalent, polar covalent, and
ionic bonds in terms of relative polarity.
79. What are dispersion forces? How is the strength of dispersion forces related to the number of electrons in a
molecule? Give an example of molecules that are attracted to each other by dispersion forces.
80. Describe a network solid and give two examples.
Chem I Chapter 8
Answer Section
MATCHING
1. ANS: C
PTS: 1
DIF: L1
REF: p. 227
OBJ: 8.2.1 Explain the result of electron sharing in covalent bonds.
STA: C.3.1 | C.3.2 | C.3.3
BLM: knowledge
2. ANS: D
PTS: 1
DIF: L1
REF: p. 226
OBJ: 8.2.1 Explain the result of electron sharing in covalent bonds.
STA: C.3.1 | C.3.2 | C.3.3
BLM: knowledge
3. ANS: B
PTS: 1
DIF: L1
REF: p. 230
OBJ: 8.2.1 Explain the result of electron sharing in covalent bonds.
STA: C.3.1 | C.3.2 | C.3.3
BLM: knowledge
4. ANS: A
PTS: 1
DIF: L1
REF: p. 231
OBJ: 8.2.2 Describe how coordinate covalent bonds are different from other covalent bonds.
STA: C.3.1 | C.3.2 | C.3.3
BLM: knowledge
5. ANS: E
PTS: 1
DIF: L1
REF: p. 248
OBJ: 8.4.1 Describe how electronegativity values determine the charge distribution in a polar molecule.
STA: C.3.1 | C.3.2 | C.3.3
BLM: knowledge
6. ANS: F
PTS: 1
DIF: L1
REF: p. 250
OBJ: 8.4.2 Evaluate the strengths of intermolecular attractions compared with the strengths of ionic and
covalent bonds.
STA: C.3.1 | C.3.2 | C.3.3
BLM: knowledge
7. ANS: D
PTS: 1
DIF: L1
REF: p. 236
OBJ: 8.2.4 Explain how the strength of a covalent bond is related to its bond dissociation energy.
STA: C.3.1 | C.3.2 | C.3.3
BLM: knowledge
8. ANS: G
PTS: 1
DIF: L1
REF: p. 238
OBJ: 8.3.1 Describe the relationship between atomic and molecular orbitals.
STA: C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: knowledge
9. ANS: B
PTS: 1
DIF: L1
REF: p. 238
OBJ: 8.3.1 Describe the relationship between atomic and molecular orbitals.
STA: C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: knowledge
10. ANS: E
PTS: 1
DIF: L1
REF: p. 240
OBJ: 8.3.2 Describe how VSEPR theory helps predict the shapes of molecules.
STA: C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: knowledge
11. ANS: F
PTS: 1
DIF: L1
REF: p. 240
OBJ: 8.3.2 Describe how VSEPR theory helps predict the shapes of molecules.
STA: C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: knowledge
12. ANS: C
PTS: 1
DIF: L1
REF: p. 250
OBJ: 8.4.2 Evaluate the strengths of intermolecular attractions compared with the strengths of ionic and
covalent bonds.
STA: C.3.1 | C.3.2 | C.3.3
BLM: knowledge
13. ANS: A
PTS: 1
DIF: L1
REF: p. 252
OBJ: 8.4.3 Explain why the properties of covalent compounds are so diverse.
STA: C.3.1 | C.3.2 | C.3.3
BLM: knowledge
MULTIPLE CHOICE
14. ANS:
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D
PTS: 1
DIF: L2
REF: p. 222
8.1.1 Identify the information a molecular formula provides.
C.3.1 | C.3.2 | C.3.3
BLM: comprehension
A
PTS: 1
DIF: L1
REF: p. 227
8.2.1 Explain the result of electron sharing in covalent bonds.
C.3.1 | C.3.2 | C.3.3
BLM: comprehension
A
PTS: 1
DIF: L1
REF: p. 223
8.1.1 Identify the information a molecular formula provides.
C.3.1 | C.3.2 | C.3.3
BLM: knowledge
C
PTS: 1
DIF: L2
REF: p. 226
8.2.1 Explain the result of electron sharing in covalent bonds.
C.3.1 | C.3.2 | C.3.3
BLM: comprehension
B
PTS: 1
DIF: L2
REF: p. 226
8.2.1 Explain the result of electron sharing in covalent bonds.
C.3.1 | C.3.2 | C.3.3
BLM: comprehension
D
PTS: 1
DIF: L2
REF: p. 230
8.2.1 Explain the result of electron sharing in covalent bonds.
C.3.1 | C.3.2 | C.3.3
BLM: comprehension
B
PTS: 1
DIF: L2
REF: p. 227
8.2.1 Explain the result of electron sharing in covalent bonds.
C.3.1 | C.3.2 | C.3.3
BLM: application
D
PTS: 1
DIF: L3
REF: p. 226 | p. 227
8.2.1 Explain the result of electron sharing in covalent bonds.
C.3.1 | C.3.2 | C.3.3
BLM: comprehension
A
PTS: 1
DIF: L2
REF: p. 226
8.1.2 Describe the representative units that define molecular compounds and ionic compounds.
C.3.1 | C.3.2 | C.3.3
BLM: comprehension
D
PTS: 1
DIF: L2
REF: p. 238 | p. 244
8.3.1 Describe the relationship between atomic and molecular orbitals.
C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: application
A
PTS: 1
DIF: L2
REF: p. 230
8.2.1 Explain the result of electron sharing in covalent bonds.
C.3.1 | C.3.2 | C.3.3
BLM: application
B
PTS: 1
DIF: L2
REF: p. 230
8.2.1 Explain the result of electron sharing in covalent bonds.
C.3.1 | C.3.2 | C.3.3
BLM: application
B
PTS: 1
DIF: L1
REF: p. 224
8.1.2 Describe the representative units that define molecular compounds and ionic compounds.
C.3.1 | C.3.2 | C.3.3
BLM: knowledge
D
PTS: 1
DIF: L2
REF: p. 232
8.2.2 Describe how coordinate covalent bonds are different from other covalent bonds.
C.3.1 | C.3.2 | C.3.3
BLM: comprehension
A
PTS: 1
DIF: L2
REF: p. 233
8.2.4 Explain how the strength of a covalent bond is related to its bond dissociation energy.
C.3.1 | C.3.2 | C.3.3
BLM: application
B
PTS: 1
DIF: L2
REF: p. 236 | p. 237
8.2.4 Explain how the strength of a covalent bond is related to its bond dissociation energy.
C.3.1 | C.3.2 | C.3.3
BLM: application
30. ANS:
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46. ANS:
A
PTS: 1
DIF: L2
REF: p. 237
8.2.5 Describe how resonance structures are used.
STA: C.3.1 | C.3.2 | C.3.3
comprehension
D
PTS: 1
DIF: L2
REF: p. 235
8.2.3 Identify some exceptions to the octet rule.
STA: C.3.1 | C.3.2 | C.3.3
application
D
PTS: 1
DIF: L2
REF: p. 237
8.2.5 Describe how resonance structures are used.
STA: C.3.1 | C.3.2 | C.3.3
comprehension
C
PTS: 1
DIF: L1
REF: p. 240
8.3.1 Describe the relationship between atomic and molecular orbitals.
C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: comprehension
C
PTS: 1
DIF: L1
REF: p. 241
8.3.1 Describe the relationship between atomic and molecular orbitals.
C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: comprehension
D
PTS: 1
DIF: L2
REF: p. 240
8.3.1 Describe the relationship between atomic and molecular orbitals.
C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: comprehension
C
PTS: 1
DIF: L2
REF: p. 241
8.3.1 Describe the relationship between atomic and molecular orbitals.
C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: comprehension
B
PTS: 1
DIF: L2
REF: p. 241
8.3.1 Describe the relationship between atomic and molecular orbitals.
C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: comprehension
D
PTS: 1
DIF: L2
REF: p. 240 | p. 241
8.3.1 Describe the relationship between atomic and molecular orbitals.
C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: comprehension
D
PTS: 1
DIF: L2
REF: p. 241
8.3.1 Describe the relationship between atomic and molecular orbitals.
C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: comprehension
A
PTS: 1
DIF: L1
REF: p. 242
8.3.2 Describe how VSEPR theory helps predict the shapes of molecules.
C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: knowledge
A
PTS: 1
DIF: L1
REF: p. 242
8.3.2 Describe how VSEPR theory helps predict the shapes of molecules.
C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: knowledge
A
PTS: 1
DIF: L2
REF: p. 243
8.3.2 Describe how VSEPR theory helps predict the shapes of molecules.
C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: comprehension
C
PTS: 1
DIF: L1
REF: p. 244
8.3.3 Identify the ways in which orbital hybridization is useful in describing molecules.
C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: knowledge
C
PTS: 1
DIF: L1
REF: p. 245
8.3.3 Identify the ways in which orbital hybridization is useful in describing molecules.
C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: knowledge
C
PTS: 1
DIF: L1
REF: p. 244
8.3.3 Identify the ways in which orbital hybridization is useful in describing molecules.
C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: knowledge
D
PTS: 1
DIF: L2
REF: p. 245
47.
48.
49.
50.
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
OBJ: 8.3.3 Identify the ways in which orbital hybridization is useful in describing molecules.
STA: C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: comprehension
ANS: C
PTS: 1
DIF: L2
REF: p. 245
OBJ: 8.3.3 Identify the ways in which orbital hybridization is useful in describing molecules.
STA: C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: application
ANS: B
PTS: 1
DIF: L2
REF: p. 245
OBJ: 8.3.3 Identify the ways in which orbital hybridization is useful in describing molecules.
STA: C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: application
ANS: C
PTS: 1
DIF: L2
REF: p. 248 | p. 249
OBJ: 8.4.1 Describe how electronegativity values determine the charge distribution in a polar molecule.
STA: C.3.1 | C.3.2 | C.3.3
BLM: application
ANS: C
PTS: 1
DIF: L2
REF: p. 248 | p. 249
OBJ: 8.4.1 Describe how electronegativity values determine the charge distribution in a polar molecule.
STA: C.3.1 | C.3.2 | C.3.3
BLM: application
ANS: A
PTS: 1
DIF: L3
REF: p. 248 | p. 249
OBJ: 8.4.1 Describe how electronegativity values determine the charge distribution in a polar molecule.
STA: C.3.1 | C.3.2 | C.3.3
BLM: application
ANS: A
PTS: 1
DIF: L2
REF: p. 248 | p. 249
OBJ: 8.4.1 Describe how electronegativity values determine the charge distribution in a polar molecule.
STA: C.3.1 | C.3.2 | C.3.3
BLM: comprehension
ANS: B
PTS: 1
DIF: L1
REF: p. 251
OBJ: 8.4.2 Evaluate the strengths of intermolecular attractions compared with the strengths of ionic and
covalent bonds.
STA: C.3.1 | C.3.2 | C.3.3
BLM: knowledge
ANS: B
PTS: 1
DIF: L1
REF: p. 251
OBJ: 8.4.2 Evaluate the strengths of intermolecular attractions compared with the strengths of ionic and
covalent bonds.
STA: C.3.1 | C.3.2 | C.3.3
BLM: knowledge
ANS: B
PTS: 1
DIF: L1
REF: p. 251
OBJ: 8.4.2 Evaluate the strengths of intermolecular attractions compared with the strengths of ionic and
covalent bonds.
STA: C.3.1 | C.3.2 | C.3.3
BLM: knowledge
ANS: B
PTS: 1
DIF: L1
REF: p. 250
OBJ: 8.4.2 Evaluate the strengths of intermolecular attractions compared with the strengths of ionic and
covalent bonds.
STA: C.3.1 | C.3.2 | C.3.3
BLM: knowledge
ANS: D
PTS: 1
DIF: L2
REF: p. 251
OBJ: 8.4.2 Evaluate the strengths of intermolecular attractions compared with the strengths of ionic and
covalent bonds.
STA: C.3.1 | C.3.2 | C.3.3
BLM: comprehension
ANS: A
PTS: 1
DIF: L2
REF: p. 251
OBJ: 8.4.2 Evaluate the strengths of intermolecular attractions compared with the strengths of ionic and
covalent bonds.
STA: C.3.1 | C.3.2 | C.3.3
BLM: comprehension
ANS: B
PTS: 1
DIF: L1
REF: p. 252
OBJ: 8.4.3 Explain why the properties of covalent compounds are so diverse.
STA: C.3.1 | C.3.2 | C.3.3
BLM: knowledge
ANS: D
PTS: 1
DIF: L2
REF: p. 251
OBJ: 8.4.3 Explain why the properties of covalent compounds are so diverse.
STA: C.3.1 | C.3.2 | C.3.3
BLM: comprehension
NUMERIC RESPONSE
61. ANS: 7
PTS:
OBJ:
STA:
62. ANS:
1
DIF: L2
REF: p. 227
8.2.1 Explain the result of electron sharing in covalent bonds.
C.3.1 | C.3.2 | C.3.3
BLM: application
4
PTS:
OBJ:
STA:
63. ANS:
1
DIF: L1
REF: p. 228
8.2.1 Explain the result of electron sharing in covalent bonds.
C.3.1 | C.3.2 | C.3.3
BLM: knowledge
2
PTS:
OBJ:
STA:
64. ANS:
1
DIF: L1
REF: p. 226
8.2.1 Explain the result of electron sharing in covalent bonds.
C.3.1 | C.3.2 | C.3.3
BLM: knowledge
3
PTS:
OBJ:
STA:
65. ANS:
1
DIF: L2
REF: p. 228
8.2.1 Explain the result of electron sharing in covalent bonds.
C.3.1 | C.3.2 | C.3.3
BLM: application
1
PTS:
OBJ:
STA:
66. ANS:
1
DIF: L2
REF: p. 228
8.2.1 Explain the result of electron sharing in covalent bonds.
C.3.1 | C.3.2 | C.3.3
BLM: comprehension
4
PTS:
OBJ:
STA:
67. ANS:
1
DIF: L2
REF: p. 228
8.2.1 Explain the result of electron sharing in covalent bonds.
C.3.1 | C.3.2 | C.3.3
BLM: comprehension
4
PTS:
OBJ:
STA:
68. ANS:
1
DIF: L2
REF: p. 230
8.2.1 Explain the result of electron sharing in covalent bonds.
C.3.1 | C.3.2 | C.3.3
BLM: comprehension
3
PTS:
OBJ:
STA:
69. ANS:
1
DIF: L3
REF: p. 228
8.2.1 Explain the result of electron sharing in covalent bonds.
C.3.1 | C.3.2 | C.3.3
BLM: application
3
PTS:
OBJ:
STA:
70. ANS:
1
DIF: L3
REF: p. 229
8.2.1 Explain the result of electron sharing in covalent bonds.
C.3.1 | C.3.2 | C.3.3
BLM: application
105
PTS: 1
DIF: L1
REF: p. 243
OBJ: 8.3.2 Describe how VSEPR theory helps predict the shapes of molecules.
STA: C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: knowledge
ESSAY
71. ANS:
Bond dissociation energy is the energy required to break a single bond. The greater the bond dissociation
energy, the more stable the compound. Due in part to the high bond dissociation energy of carbon-carbon
bonds, carbon compounds are not very reactive chemically.
PTS: 1
DIF: L3
REF: p. 236 | p. 237
OBJ: 8.2.4 Explain how the strength of a covalent bond is related to its bond dissociation energy.
STA: C.3.1 | C.3.2 | C.3.3
BLM: synthesis
72. ANS:
Yes, sulfur and phosphorus can expand the octet. They can have 12 or 10 valence electrons, respectively,
when combined with small halogens. In PCl , phosphorus has 10 valence electrons.
PTS: 1
DIF: L2
REF: p. 235
OBJ: 8.2.3 Identify some exceptions to the octet rule.
STA: C.3.1 | C.3.2 | C.3.3
BLM: application
73. ANS:
When two atoms combine, the overlap of their atomic orbitals produces molecular orbitals. An atomic orbital
belongs to a particular atom, whereas a molecular orbital belongs to a molecule as a whole. Much like an
atomic orbital, two electrons are required to fill a molecular orbital. A bonding orbital is a molecular orbital
occupied by the two electrons of a covalent bond.
PTS: 1
DIF: L3
REF: p. 240
OBJ: 8.3.1 Describe the relationship between atomic and molecular orbitals.
STA: C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: application
74. ANS:
A pi bond is the bond formed as a result of the side-by-side overlap of two p orbitals. A sigma bond is the
bond that results from a combination of two s orbitals, two p orbitals, or a p and an s orbital. Orbital overlap
in pi bonding is less extensive than that for sigma bonding. Therefore, pi bonds tend to be weaker than sigma
bonds.
PTS: 1
DIF: L3
REF: p. 240 | p. 241
OBJ: 8.3.1 Describe the relationship between atomic and molecular orbitals.
STA: C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: analysis
75. ANS:
VSEPR (valence-shell electron-pair repulsion) theory states that because electron pairs repel, molecules adjust
their shapes so that the valence-electron pairs, both bonding and non-bonding, are as far apart as possible.
Methane, CH , for example, has four bonding electron pairs and no unshared pairs. The bonding pairs are
farthest apart when the angle between the central carbon and each of its attached hydrogens is 109.5 . This is
the angle that is observed experimentally.
PTS: 1
DIF: L3
REF: p. 242
OBJ: 8.3.2 Describe how VSEPR theory helps predict the shapes of molecules.
STA: C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: application
76. ANS:
In orbital hybridization, two or more different atomic orbitals mix to form the same total number of
equivalent hybrid orbitals. For instance, the s and p orbitals of an atom combine to make hybrid orbitals
having the character of both the s orbital and the p orbital. These hybrid orbitals are equivalent. Orbital
hybridization occurs in the methane molecule in which one 2s orbital and three 2p orbitals hybridize to form
four sp orbitals.
PTS: 1
DIF: L3
REF: p. 244
OBJ: 8.3.3 Identify the ways in which orbital hybridization is useful in describing molecules.
STA: C.3.1 | C.3.2 | C.3.3 | C.3.4
BLM: application
77. ANS:
Sample Answer: NO2 is an molecule that does not satisfy the octet rule. The Lewis dot structure for nitrogen
dioxide is
It does not satisfy the octet rule because each atom in the molecule only has access to 7 electrons, instead of
the eight required, as shown by the circled atoms.
This molecule can be represented by a resonance structure in which the nitrogen atom and one oxygen atom at
a time appear to have a stable octet. The actual bonding is a hybrid, or mixture, of the extremes represented by
the resonance forms.
PTS: 1
DIF: L3
REF: p. 235 | p. 237
OBJ: 8.2.3 Identify some exceptions to the octet rule. | 8.2.5 Describe how resonance structures are used.
STA: C.3.1 | C.3.2 | C.3.3
BLM: evaluation
78. ANS:
The relative electronegativity of the two bonded atoms determines the polarity of a bond. If the difference in
electronegativities between the two atoms is less than 0.4, the bond is nonpolar covalent. If the difference in
electronegativities between the two atoms is 0.4 to 1.0, the bond is moderately polar covalent. If the
difference in electronegativities between the two atoms is 1.0 to 2.0, the bond is highly polar covalent. If the
difference in electronegativities between the two atoms is more than 2.0, the bond is ionic.
PTS: 1
DIF: L3
REF: p. 247 | p. 280 | p. 249
OBJ: 8.4.1 Describe how electronegativity values determine the charge distribution in a polar molecule.
STA: C.3.1 | C.3.2 | C.3.3
BLM: analysis
79. ANS:
Dispersion forces are the weakest of all molecular interactions, and are thought to be caused by the motion of
electrons. Generally, the strength of dispersion forces increases as the number of electrons in a molecule
increases. Diatomic molecules of halogen elements are an example of molecules whose attraction for one
another is caused by dispersion forces.
PTS: 1
DIF: L3
REF: p. 251
OBJ: 8.4.2 Evaluate the strengths of intermolecular attractions compared with the strengths of ionic and
covalent bonds.
STA: C.3.1 | C.3.2 | C.3.3
BLM: synthesis
80. ANS:
Network solids are substances in which all of the atoms are covalently bonded to each other. Melting these
substances requires breaking covalent bonds throughout the solid. Two examples are diamond and silicon
carbide.
PTS: 1
DIF: L2
REF: p. 252
OBJ: 8.4.3 Explain why the properties of covalent compounds are so diverse.
STA: C.3.1 | C.3.2 | C.3.3
BLM: comprehension