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. To view the molecules interactively, please use RASMOL, a computer application which is available for both Macs and PCs and can be downloaded at the RASMOL site. To download the pdb files (refers to the protein databank method of saving atomic coordinates for a molecule) for viewing and rotating the compounds used in this experiment, please click on the appropriate molecule name or VSEPR shape in the tables below. (Note: If you want to view multiple compounds simultaneously, please download each pdb file and save on your computer. Then open RASMOL outside of Netscape.)

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.