Valence Shell Electron Pair Repulsion


NOTE: VSEPR is also known as Electron Domain Theory

Below are two tables containing the lewis structures and VSEPR shapes of various molecules. The molecules shown below can be automatically rotated and viewed using MDL Chemscape Chime. Alternatively, the pdb files for the molecules can be downloaded and opened using RASMOL, a software program which allows for greater control over viewing and rotating.

Two computer applications, Chemscape Chime and RASMOL, are required to download, view, and rotate the molecules which are saved in a pdb format (refers to the protein databank method of saving atomic coordinates for a molecule) and a MDL mol format. These programs are available for both Macs and PCs and can be downloaded from the following locations:

The VSEPR model gives simple rules to predict molecular shape. This model assumes that bonding and nonbonding (lone-pair) electron pairs about a central atom experience repulsions from one another that cause these electron pairs to move as far apart as possible. The geometry is determined by the steric number (SN), which is the sum of the bonded atoms to the central atom and the lone pairs around the central atom.


Table for Steric numbers 2-4 Table for Steric numbers 5 and 6
Table 1 includes the following molecules: Table 2 includes the following molecules:
BeH2
CH2
BF3
CH4
NH3
H2S
PF5
BrF3
TeCl4
SF6
XeF4
XeF2

To check out other visualization modules
such as animated atomic orbitals, go to the Lecture Projects page.


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Last modified: June 15, 2006