10/7/2014
ALEKS Alex H. Yuan - 10/07/2014 7:31:19 PM EDT - Copyright © 2014 UC Regents and ALEKS Corporation
Alex H. Yuan - 10/07/2014 7:31:19 PM EDT
General Chemistry (First Semester) / Chem 110 FA 2014 – CH110 FA14 S25-36 (Dr.
Barber)
1.
Predicting bond angles in molecules with one central atom and no octet-rule
exceptions
What is the angle between two of the carbon-chlorine bonds in the carbon tetrachloride
(
) molecule?
To find the bond angles in a molecule you must first decide its shape. You can do so by
using the Valence Shell Electron Pair Repulsion (VSEPR) model.
Begin by drawing the Lewis structure of the carbon tetrachloride molecule to find the
number of electron groups around the central atom.
Cl
Cl
C
Cl
Cl
In this case, there are
groups of electrons around the central atom.
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Each of the following counts as
group of valence electrons:
One lone pair.
One single bond.
One double or triple bond.
It's worth emphasizing that a double or triple bond counts as only one group of
electrons, not two or three.
There are groups of electrons around the central carbon atom in the carbon
tetrachloride molecule: four single bonds.
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10/7/2014
ALEKS Alex H. Yuan - 10/07/2014 7:31:19 PM EDT - Copyright © 2014 UC Regents and ALEKS Corporation
Next, find the arrangement of electron groups that keeps them farthest from each other. To
do so you might want to memorize the following list of arrangements:
If the molecule has
apart, and so forth.
electron groups, the structure labeled
keeps them the farthest
Since the carbon tetrachloride molecule has electron groups, the electron-group
structure labeled will keep them farthest apart.
Since the shape of the carbon tetrachloride molecule is tetrahedral, the angle between two
of the carbon-chlorine bonds is
The angle in degrees between two of the carbon-chlorine bonds is
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