Question

Explain the VSEPR theory.

Answer 1

• The shape of the molecule depends upon the number of electron pairs (bonded or non-bonded) around the central atom.
• The electron pairs around the central atom tend to repel one another since the electron clouds are negatively charged.
• The electron pairs in space tend to occupy such positions that they are at maximum distance apart and the repulsive interactions are minimum.
• A multiple bond is treated as if it is a single bond and the electron pairs which constitute the bond may be regarded as single pairs.
• Where two or more resonance structures can represent a molecule, the VSEPR model is applicable to any such structure.
• Gillespie and Nyholmn stated that the electron pairs existing as lone pairs cause greater repulsive interactions as compared to bonded electron pairs. In the light of this, the repulsive interactions follow the order:

Lone pair – Lone pair > Lone pair – Bond pair > Bond pair – Bond pair