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.
2.
3.
4.
5.
6.
a depiction of the arrangement of atoms in molecules and polyatomic ions
a covalent bond in which only one pair of electrons is shared
a covalent bond in which two pairs of electrons are shared
a covalent bond in which the shared electron pair comes from only one of the atoms
a covalent bond between two atoms of significantly different electronegativities
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.
8.
9.
10.
11.
12.
13.
energy needed to break a single bond between two covalently bonded atoms
symmetrical bond along the axis between the two nuclei
molecular orbital that can be occupied by two electrons of a covalent bond
109.5
shapes adjust so valence-electron pairs are as far apart as possible
attraction between polar molecules
crystal in which all the atoms are covalently bonded to each other
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
____ 14. Which is a typical characteristic of an ionic compound?
a. Electron pairs are shared among atoms.
b. The ionic compound has a low solubility in water.
c. The ionic compound is described as a molecule.
d. The ionic compound has a high melting point.
____ 15. What is shown by the structural formula of a molecule or polyatomic ion?
a. the arrangement of bonded atoms
c. the number of metallic bonds
b. the number of ionic bonds
d. the shapes of molecular orbitals
____ 16. Which of these elements does not exist as a diatomic molecule?
a. Ne
c. H
b. F
d. I
____ 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.
____ 18.
____ 19.
____ 20.
____ 21.
____ 22.
____ 23.
c. Two atoms share two electrons.
d. Two atoms share one electron.
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
Which of the following elements can form diatomic molecules held together by triple covalent
bonds?
a. carbon
c. fluorine
b. oxygen
d. nitrogen
Which noble gas has the same electron configuration as the oxygen in a water molecule?
a. helium
c. argon
b. neon
d. xenon
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
Which of the following is the name given to the pairs of valence electrons that do not participate
in bonding in diatomic oxygen molecules?
a. unvalenced pair
c. inner pair
b. outer pair
d. unshared pair
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
c. 2s 2p 3s
b. 2s 2p 3s
d. 2s 2p
____ 24. Which of the following diatomic molecules is joined by a double covalent bond?
a.
c.
b.
d.
____ 25. A molecule with a single covalent bond is ____.
a. CO
c. CO
b. Cl
d. N
____ 26. When one atom contributes both bonding electrons in a single covalent bond, the bond is called
a(n) ____.
a. one-sided covalent bond
c. coordinate covalent bond
b. unequal covalent bond
d. ionic covalent bond
____ 27. Once formed, how are coordinate covalent bonds different from other covalent bonds?
a. They are stronger.
c. They are weaker.
b. They are more ionic in character.
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
c. O—H
b. H—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
c. 2 only
b. 1 only
d. 2 or more
____ 31. In which of the following compounds is the octet expanded to include 12 electrons?
a. H S
c. PCl
b. PCl
d. SF
____ 32. How many electrons can occupy a single molecular orbital?
a. 0
c. 2
b. 1
d. 4
____ 33. Molecular orbital theory is based upon which of the following models of the atom?
a. classical mechanical model
c. quantum mechanical model
b. Bohr 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
c. pi bond
b. sigma bond
d. beta bond
____ 35. How is a pair of molecular orbitals formed?
a. by the splitting of a single atomic orbital
b. by the reproduction of a single atomic orbital
c. by the overlap of two atomic orbitals from the same atom
d. by the 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
c. pi bond
b. beta 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
c. d only
b. p 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
c. mobile electrons
b. inner shell electrons
d. the electrons closest to the nuclei
____ 41. The shape of the methane molecule is called ____.
a. tetrahedral
c. four-cornered
b. square
d. planar
____ 42. What causes water molecules to have a bent shape, according to VSEPR theory?
a. repulsive forces between unshared pairs of electrons
____ 43.
____ 44.
____ 45.
____ 46.
____ 47.
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
Which of the following theories provides information concerning both molecular shape and
molecular bonding?
a. molecular orbital theory
c. orbital hybridization theory
b. VSEPR theory
d. Bohr atomic theory
Experimental evidence suggests that the H—C—H bond angles in ethene, C H , are ____.
a. 90
c. 120
b. 109.5
d. 180
What type of hybrid orbital exists in the methane molecule?
a. sp
c. sp
b. sp
d. sp d
What is the shape of a molecule with a triple bond?
a. tetrahedral
c. bent
b. pyramidal
d. linear
What type of hybridization occurs in the orbitals of a carbon atom participating in a triple bond
with another carbon atom?
a.
c.
b.
d.
____ 48. How many pi bonds are formed when sp hybridization occurs in ethene, C H ?
a. 0
c. 2
b. 1
d. 3
____ 49. Which of the following atoms acquires the most negative charge in a covalent bond with
hydrogen?
a. C
c. O
b. Na
d. S
____ 50. A bond formed between a silicon atom and an oxygen atom is likely to be ____.
a. ionic
c. polar covalent
b. coordinate covalent
d. nonpolar covalent
____ 51. Which of the following covalent bonds is the most polar?
a. H—F
c. H—H
b. H—C
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
c. H—O—H plane of the molecule
b. geometric center of the molecule
d. oxygen region of the molecule
____ 53. What is thought to cause the dispersion forces?
a. attraction between ions
c. sharing of electron pairs
b. motion of electrons
d. differences in electronegativity
____ 54. Which of the forces of molecular attraction is the weakest?
a. dipole interaction
c. hydrogen bond
b. dispersion
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
____ 56.
____ 57.
____ 58.
____ 59.
____ 60.
d. attraction between ions
What are the weakest attractions between molecules?
a. ionic forces
c. covalent forces
b. Van der Waals forces
d. hydrogen forces
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
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.
Which type of solid has the highest melting point?
a. ionic solid
c. metal
b. network solid
d. nonmetallic solid
What is required in order to melt a network solid?
a. breaking Van der Waals bonds
c. breaking hydrogen bonds
b. breaking ionic 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. Explain what a polar molecule is. Provide an example.
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.