Question

What effect does a lone electron pair have on molecular shape?

Answer 1

Using the VSPER theory, the effect of lone pairs on molecular shape can be discussed.

There are 3 types of electron pairs present in a molecular shape: bond pair -bond pair, lone pair - bond pair, lone pair - lone pair.

Strength of repulsions between these three types of pair follows the order:

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

Whenever there is an addition of lone pairs to the geometry, some distortions take place which decreases the bond angles and some asymmetry is attained in the original molecular shape.