Introduction  The Model (VSEPR)  Examples 
The electrons around the atoms in a molecule repel each other. They move to be as far apart as possible while still maintaining the bonding within the molecule. The procedure for using the model is as follows:
1) Determine the correct Lewis
structure for the molecule.
If it is a diatomic (has only two atoms) it is linear and falls into
the AX category. If it has 3 or
more atoms continue with step 2.
2) Count the number of electron groups around the central atom. A group of electrons is a bond, a nonbonding electron pair, or occasionally an unpaired nonbonding electron. Each triple or double bond counts as only one group for the purposes of this model.
3) Based on this number of groups around the central atom the
molecule falls into one of six basic
categories. Within each category there are a number of different
names for the shapes depending upon the number of atoms and nonbonding
groups around the central atom.
Number of
Groups 
Basic Shape (click
links below to see examples)

SubShapes A = central atom X = atom attached to central atom E = nonbonding electron group on central atom 

Diatomic
(any number) 
Linear Diatomic 
Generic Formula AX 
Shape Name Linear 
2 
Linear
Triatomic 
AX_{2} 
Linear 
3 
Trigonal
Planar 
AX_{3} AX_{2}E 
Trigonal Planar Bent 
4 
Tetrahedral 
AX_{4} AX_{3}E AX_{2}E_{2} 
Tetrahedral Trigonal Pyramidal Bent 
5 
Trigonal
Bipyramidal 
AX_{5} AX_{4}E AX_{3}E_{2} AX_{2}E_{3} 
Trigonal Bipyramidal SeeSaw TShaped Linear 
6 Last Table Update:
4/5/07
Expires:  J. Gutow 
Octahedral 
AX_{6} AX_{5}E AX_{4}E_{2} _{} 
Octahedral Square Pyramidal Square Planar 