What is valence shell electron pair repulsion theory? Us e methane and water molecule to explain this theory

Answer 1

Valence shell electron pair repulsion (VSEPR) theory states that the arrangement of atoms in a molecule is determined by minimizing the repulsions between electron pairs in the valence shell of the central atom. According to this theory, electron pairs (whether bonding or non-bonding) repel each other and will arrange themselves in a way that maximizes their separation.

In the case of methane (CH4), there are four pairs of electrons around the central carbon atom. These electron pairs repel each other equally, leading to a tetrahedral molecular geometry with bond angles of approximately 109.5 degrees. This arrangement minimizes electron pair repulsions and provides the most stable configuration for the molecule.

On the other hand, in the case of water (H2O), there are two bonding pairs and two lone pairs of electrons around the central oxygen atom. The lone pairs exert greater repulsion than bonding pairs, causing a slight distortion in the molecular geometry. The resulting shape is bent with bond angles of approximately 104.5 degrees, again allowing for the maximum separation of electron pairs and creating a stable molecule.

Overall, VSEPR theory helps explain the geometric shapes of molecules based on the repulsions between electron pairs, providing insight into their chemical properties and behaviors.