Valence Shell Electron Pair Repulsion (VSEPR) Theory

VSEPR theory focuses on the electron pairs present in the valence shell of the central atom of the molecule and can be stated in terms of two postulates.

Postulate 1

The electron pairs (both bonding and non-bonding) around the central atom in a molecule arrange themselves in space in such a way that they minimize their mutual repulsion.

The chemical bonds in the molecule will be energetically most stable when they are as far apart from each other as possible.

Postulate 2

The repulsion of a lone pair of electrons for another lone pair is greater than that between a bond pair and a lone pair which in turn is greater than that between two bond pairs. The order of repulsive force between different possibilities is:

lone pair - lone pair > lone pair - bond pair > bond pair - bond pair