Ncert Exercises & Solutions

3.13 Explain why cation are smaller and anions larger in radii than their parent atoms?

A cation has a fewer number of electrons than its parent atom, while its nuclear charge

remains the same. As a result, the attraction of electrons to the nucleus is more in a cation

than in its parent atom. Therefore, a cation is smaller in size than its parent atom. On the

other hand, an anion has one or more electrons than its parent atom, resulting in an

increased repulsion among the electrons and a decrease in the effective nuclear charge.

As a result, the distance between the valence electrons and the nucleus is more in anions

than in it’s the parent atom. Hence, an anion is larger in radius than its parent atom.