(i) The electronic configuration of an atom is one of the important factor which affects the value of ionization potential and electron gain enthalpy. Explain.
(ii) Explain why cation are smaller and anions are larger in radii than their parent atoms?

Explanation

(i) 1. Electronic configuration of an atom affects the value of ionization potential and electron gain enthalpy.
2. Half filled valence shell electronic configuration and completely filled valence shell electronic configuration are more stable than partially filled electronic configuration.
3. For e.g. Beryllium `(Z=4)1s^(2)2s^(2)`(completely filled electronic configuration)
Nitrogen `(Z=7)1s^(2)2s^(2)2p_(x)^(1)2p_(y)1 2p_(z)^(1)`
(half filled electronic configuration)
Both beryllium and nitrogen have high ionization energy due to more stable nature.
4. In the case of beryllium `(1s^(2)2s^(2))`, nitrogen `(1s^(2)2s^(2)2p^(3))` the addition of extra electron will disturb their stable electronic configuration and they have almost zero electron affinity.
5. Noble gases have stable ns np configuration and the addition of further electron is unfavorable and they have zero electron affinity.
(ii) A cation is smaller than the parent atom because it has fewer electrons while its nuclear charge remains the same. The size of anion will be larger than that of parent atom because the addition of one or more electrons would result in increased repulsion among the electrons and a decrease in effective nuclear charge.