(a) The cations are smaller than their parent atoms due to the following reasons:
Disappearance of the valence shell. Increase of effective nuclear charge
(b) The anions are larger than their parent atoms due to the following reason:
An increase in the number of electrons in the valence shell reduces the effective nuclear charge due to greater mutual shielding by the electrons. As a result, electron cloud expands, i.e., the ionic radius increases.
