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

Explanation

Removal of one or more electrons from the parent atom increases the effective nuclear charge. Thus, the remaining electrons experience a greater nuclear pull which results in the decrease of radius. This is why cations are always smaller in radii than the parent atoms. On the other hand, addition of one or more electrons to the parent atom decreases the effective nuclear charge. Thus, the electrons experience a lesser nuclear pull. This results in an increase in the radius. This is why anions are always larger in radii than the parent atoms.