Humber Admissions Practice Test

In the context of molecular shapes, what is repelled according to VSPER theory?

1. Nucleus of the atom

2. Pairs of valence electrons

3. Bonding pairs of electrons

4. Non-bonding electron pairs

The correct answer is: Pairs of valence electrons

VSEPR theory, which stands for Valence Shell Electron Pair Repulsion theory, is centered on the idea that electron pairs around a central atom will arrange themselves to minimize repulsion between them. In this context, pairs of valence electrons, which consist of both bonding pairs and non-bonding pairs, are considered the primary factors that govern the arrangement of molecules. Repulsion occurs because electrons are negatively charged; therefore, any two groups of electrons will naturally push away from one another to minimize this repulsive force. Valence electrons can either be shared in bonds (bonding pairs) or remain unshared (non-bonding pairs), and both types of pairs exert repulsive forces. However, non-bonding pairs of electrons exert slightly stronger repulsive effects compared to bonding pairs because they are localized around a single atom and do not contribute to bonding. Choosing pairs of valence electrons encompasses both types of electron pairs involved in molecular geometry. This means that they play a crucial role in determining the shape of the molecule as they will arrange themselves to be as far apart from each other as possible. Thus, the correct answer reflects the understanding that it is indeed the pairs of valence electrons that are subject to repulsion according to VSEPR