Solutions to Molecular Geometry & Bonding
GEOMETRY EXERCISES
1. Determine the molecular shape and polarity of each of the following common substances.
CCl4
PF3
H2S
Lewis structure
4
4
4
e-pair geometry
Tetrahedral
Tetrahedral
Tetrahedral
Molecular shape
Tetrahedral
Trigonal Pyramid
Bent (109.5)
NO
YES
YES
Steric number
Sketch
w/ Bond angles
(incl. deviations)
& bond
polarities
Polar Molecule?
(Yes or No)
2. Chloramine (NH2Cl) is often used as a substitute for chlorine (Cl2) to disinfect municipal water
systems. Determine the molecular shape, bond angles, and polarity of chloramine. Based
upon polarity considerations, which do you think is more soluble in water, chloramine or chlorine?
Chem 131
Solutions to Molecular Geometry
Page 1
3. In last week’s discussion handout, you determined the Lewis structures of sulfur dioxide SO2,
nitrate ion NO3−, and chlorine trifluoride ClF3. Determine the molecular shapes and polarities of
each of these substances.
SO2
NO3−
ClF3
3
3
5
e-pair geometry
Trigonal planar
Trigonal planar
Trigonal bipyramidal
Molecular shape
Bent (120)
Trigonal planar
T-shaped
YES
NO (ion)
YES
Lewis structure
Steric number
Sketch
w/ Bond angles
(incl. deviations)
& bond
polarities
Polar Molecule?
(Yes or No)
4. Methanol (CH3OH), also known as methyl alcohol or wood alcohol, is toxic and hence is often
used to “denature” ethanol (drinking alcohol) so that industrial users of ethanol can avoid paying
high liquor alcohol taxes. Draw the Lewis structure of methanol, and determine the bond angles
around each of the “inner atoms” (C & O) in this molecule.
Chem 131
Solutions to Molecular Geometry
Page 2
BONDING EXERCISES
5. Analyze the bonding in each of the substances whose geometries were determined in problem 1
earlier. CCl4 has been done for you as an example.
Perspective
drawing
CCl4
PF3
Cl
F
C
Cl
Cl
↑↓
Non-bonded
e-configuration
Cl
↑
↑
Bonded econfiguration
P
2p
↑↓
↑↓ ↑↓ ↑
3s
F
↑↓
↑
↑↓
↑↓
↑↓ ↑↓ ↑
P
F
↑↓
Chem 131
↑↓ ↑↓ ↑
↑
↑↓
3p
H
↑
S
↑↓ ↑↓ ↑ ↑
3sp3
H
P
Cl
4 σ bonds
↑↓ ↑ ↑
3s
2p
:
F
Cl
..
sp3
F
Cl
H
1s
2s
3p
C
S
2p
3sp3
↑↓ ↑↓ ↑
S
1s
↑↓ ↑ ↑ ↑
Cl
Balloon drawing
H
sp3
↑ ↑
3s
↑ ↑
3p
2 sp3
Cl
↑
2s
3p
↑
:
3s
sp3
C
:
F
2s
Hybridization of
central atom
H
P
F
Cl
C
H2S
F
3 σ bonds
Solutions to Molecular Geometry
:
S
H
..
2 σ bonds
Page 3
6. Formaldehyde, also known as methanal, has the formula H2CO. Do a complete analysis of this
molecule, including drawing a Lewis structure, determining the geometry and polarity of the molecule,
and analyzing the bonding configuration.
7. Phosgene, a chemical warfare agent with the formula COCl2, has a very similar structure to
formaldehyde above. What are some of the key differences?
One difference is that while formaldehyde is very polar (dipole
moment of 2.33D), the phosgene molecule is much less polar
(1.17D), because the highly electronegative Cl atoms partially offset
the polarity caused by the O atom, resulting in a lower net molecular
polarity than that of formaldehyde.
Also, the C-Cl bonds in phosgene are longer and weaker (and
therefore more reactive) than the C-H bonds in formaldehyde.
Chem 131
Solutions to Molecular Geometry
Page 4