CHEMISTRY WKST KEY: CH. 12 REVIEW
1)
Ionic bonds involve the transfer of electrons to form ions and the ions attract each other. These bonds generally
occur between a metal (especially groups 1 and 2 metals) and a nonmetal. Covalent bonds involve the sharing
of electrons between two atoms—involves the overlapping of 2 half-filled orbitals, 1 from each atom. These
bonds generally occur between nonmetals.
2)
a) polar covalent
b) ionic
c) polar covalent
d) nonpolar covalent
3)
a)
b)
c)
d)
The above can be rotated or the dots can be in a different order around the symbol. Only thing that matters is the
number of pairs and the number of single dots must remain the same as shown.
4)
a)
b)
c) no dipoles form
5)
a)
Polar covalent bonds have an unequal sharing of electrons between two atoms so dipoles form. Nonpolar
covalent bonds involve equal sharing of electrons so no dipole forms.
b)
Polar molecules have a separation of partial charges and form a dipole within the molecule. Nonpolar
molecules do not have a separation of partial charges and will not form a dipole within the molecule.
6)
a) 120°
b) 109.5°
c) 90°
7)
a) 120°
b) <120°
c) <90° and <120°
d) 90° and 120°
Remember lone pairs require more room. The above diagrams are the Lewis structure on top and the molecular
drawing on the bottom.
8)
 Electron pairs are directed to be as far apart as possible.
 Lone pairs of electrons require more room than bonded electrons do.
9)
Atoms want 8 electrons whenever possible to become like a noble gas. When we do Lewis structures, most of the
atoms receive 8 electrons.
10)
a) 4
b) 3
c) 1
d) 3
e) 7
f) 5
11)
Look at the valence shell orbital diagrams for the two elements:
↑↓
O →
↑↓ ↑
2𝑠
↑
S→
2𝑝
↑↓
↑↓ ↑
3𝑠
↑
3𝑝
3𝑑
The O has no “d” sublevel in its valence shell. Therefore, it is locked in with just 2 half-filled orbitals to form just 2
bonds. The S has a “d” sublevel in its valence shell. When it goes to bond, the S can have electrons jump to the
3d sublevel to form 6 half-filled orbitals.
S→
↑
3𝑠
↑
↑
↑
↑
↑
3𝑝
3𝑑
With the 6 half-filled orbitals, S can form up to 6 bonds.
12)
Resonance occurs whenever there are more than one Lewis structure possible for a substance due to multiple
bonds or an odd number of electrons. It happens because the multiple bond is actually shared throughout the
whole molecule. The actual structure is called a “resonance hybrid”.
13)
NaF
SF6
BrCl3
BCl3
This compound is ionic with
ionic bonds between the ions.
This molecule is octahedral
and is nonpolar.
This molecule is T-shape and
is polar.
This molecule is trigonal
planar and is nonpolar.
ionic bonds
London Forces
dipole-dipole
London Forces
NH3
NCl3
CH3CH2CH2CH3
CH3Cl
This molecule is trigonal
pyramidal and is polar.
This molecule is trigonal
pyramidal but it has nonpolar
covalent bonds so it is
nonpolar.
This molecules is
symmetrical with all
tetrahedrals around the C’s
and is nonpolar.
This molecule is tetrahedral
but it is not symmetrical
because of the Cl so it is
polar.
hydrogen bonds
London Forces
London Forces
dipole-dipole
S
CH3CH2OH
Just a single atom so it is
considered nonpolar.
This molecule is not
symmetrical so it is polar.
London Forces
hydrogen bonds
LEWIS
Na-F
SHAPE
Na-F
ANSWER:
LEWIS
SHAPE
ANSWER:
LEWIS
SHAPE
ANSWER:
14)
NaCl is an ionic compound with ionic bonds between the particles (the Na+ and Clˉ ions). H2O is a molecule that
has hydrogen bonds between the molecules. When melting NaCl separates into the Na + and Clˉ ions. When H2O
melts it just separates into H2O molecules that are able to move around more freely. Since ionic bonds are
tremendously stronger than hydrogen bonds, it takes much more heat to melt NaCl than H 2O.
15)
The shapes of the molecules are as follows:
H2O is bent and is polar with HB.
H2S is bent and polar with DD.
CCl4 is tetrahedral and is nonpolar
with LF.
Vapor pressure increases as IMFs get weaker.
ANSWER: H2O < H2S < CCl4
16)
The shapes of the molecules are as follows:
SF4 is teeter totter and is polar
with DD.
CH3OH is not symmetrical and is
polar with HB.
CH3CH3 is symmetrical and is
nonpolar with LF.
Boiling and freezing points get higher as the IMFs get stronger.
ANSWER: CH3CH3 < SF4 < CH3OH
17)
The shapes of the molecules are as follows:
SF4
I2
ClF5
NH3
CCl4
CH3CH2CH3
ClF5 is square
pyramidal and is
polar.
NH3 is trigonal
pyramidal and is
polar.
CCl4 is tetrahedral
and is nonpolar.
CH3CH2CH3 is
symmetrical and is
nonpolar.
LEWIS
I–I
SHAPE
I2 is linear and
nonpolar.
SF4 is teeter totter
and is polar.
Rule is “like dissolves like”. Since water is polar, the polar molecules will dissolve in water.
ANSWER: SF4, ClF5, NH3
18)
a)
b)
bent
tetrahedral
trigonal
planar
trigonal
pyramidal
linear
trigonal
planar
19)
C.N.
L.P.
ELECTRONIC
SHAPE NAME
SO42ˉ
4
0
SO3
3
TeF4
BrF5
MOLECULE
HClO3
20)
LEWIS STRUCTURE
MOLECULAR
SHAPE NAME
POLARITY
tetrahedral
tetrahedral
nonpolar
0
trigonal
planar
trigonal
planar
nonpolar
4
1
trigonal
bipyramidal
teeter
totter
polar
5
1
octahedral
square
pyramidal
polar
Cl: tetrahedral
O: bent
polar
Cl: 3 Cl: 1 C: tetrahedral
O: 2 O: 2 O: tetrahedral
MOLECULAR DRAWING
PCl41+
4
0
tetrahedral
tetrahedral
nonpolar
KrF4
4
2
octahedral
square
planar
nonpolar