NAME:
Ch 08 Covalent/Molecular Compounds
Period:
STUDY GUIDE
/100
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
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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
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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 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?
____ 17.
____ 18.
____ 19.
____ 20.
____ 21.
____ 22.
____ 23.
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.
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.
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
B. oxygen
C. fluorine
D. nitrogen
Which noble gas has the same electron configuration as the oxygen in a water molecule?
A. helium
B. neon
C. argon
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
What is the representative unit in a molecular compound?
A. a molecule
C. a formula unit
B. an ion
D. shared electrons
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
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
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?
____ 40.
____ 41.
____ 42.
____ 43.
____ 44.
____ 45.
____ 46.
____ 47.
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
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
The shape of the methane molecule is ____.
A. tetrahedral
B. square
C. four-cornered
D. planar
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
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
B. 109.5
C. 120
D. 180
What type of hybrid orbital exists in the methane molecule?
A. sp
B. sp
C. sp
D. sp d
What is the shape of a molecule with a triple bond?
A. tetrahedral
B. pyramidal
C. bent
D. linear
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
C. polar covalent
B. coordinate 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
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
D. attraction between ions
____ 56. What are the weakest forces of attractions between molecules?
A. ionic
B. Van der Waals
C. covalent
D. hydrogen
____ 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
C. metal
B. network solid
D. nonmetallic solid
____ 60. 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
Short Answer - Draw the electron dot (Lewis structures) for each covalent molecule. [20 pts] Identify its shape and the
bond angle in the molecule. [10 pts]
61. CO2
O2
H2S
HCl
NH3
N2
PCl3
SiH4
SF6
BH3
Numeric Response
62. How many valence electrons does an iodine atom have?
63. What is the total number of covalent bonds normally associated with a single carbon atom in a compound?
64. How many electrons are shared in a single covalent bond?
65. How many electrons does a nitrogen atom need to gain in order to attain a noble-gas electron configuration?
66. How many unshared pairs of electrons does the nitrogen atom in ammonia possess?
67. How many electrons does carbon need to gain in order to obtain a noble-gas electron configuration?
68. How many electrons are shared in a double covalent bond?
69. How many covalent bonds are in a covalently bonded molecule containing 1 phosphorus atom and 3 chlorine atoms?
70. How many unshared pairs of electrons are in a molecule of hydrogen iodide?
71. What is the bond angle in a water molecule?