Molecular Shape Worksheet
SKILL DEVELOPMENT EXERCISES
For each of the following molecules draw a Lewis dot diagram (central
atom is underlined).
Predict its shape. Build it with the model kit. Tell if it
is polar.
chemical formula
|
valence e-
|
bond groups
|
lone pairs
|
shape
|
polar?
|
H2O
|
10
|
2
|
2
|
bent
|
yes
|
| CO2 |
16
|
2
|
0
|
linear
|
no
|
CF3Cl
|
32
|
4
|
0
|
tetrahedral
|
yes
|
| N2H4 |
14
|
3
|
1
|
trigonal pyramidal
|
no
|
| BH3 |
6
|
3
|
0
|
trigonal planar
|
no
|
| ClF3 |
28
|
3
|
2
|
T-shape
|
yes
|
ClF4+
|
34
|
4
|
1
|
seesaw
|
yes
|
ClF4-
|
36
|
4
|
2
|
square planar
|
no
|
CH2O
|
12
|
3
|
0
|
trigonal planar
|
yes
|
HCN
|
10
|
2
|
0
|
linear
|
yes
|
CRITICAL THINKING QUESTION
Lone pairs need more room than bonding pairs (which are trying to stay
close to 2 nuclei).
An atom with 5 pairs of electrons has two different bond angles: the
two axial positions are at 90° while the three equatorial positions
are at 120°. Which position would be better for a lone pair?
If a lone pair is in an axial position, it is 90° away from three
equatorial bond pairs.
If a lone pair is in an equatorial position, it is 90° away from
two axial bond pairs and 120° away from the other equatorial bond
pairs.
If you use the model kit you can see that it has more room in the
second case (equatorial preferred).
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