Within each pair of elements $\mathrm{F}$ and $\mathrm{C}\mathrm{l}$ , $\mathrm{S}$ and $\mathrm{S}\mathrm{e}$ , and $\text{Li}$and $\mathrm{Na}$ , respectively, the elements that release more energy upon an electron gain are

(i) Electron affinity of second period $\mathrm{p}$-block element is less than third period $\mathrm{p}$-block element due to small size of second period $\mathrm{p}$-block element, due to small size electron density is more and upcoming electron face extra repulsion, so energy release is less. Hence, EA order: $\mathrm{F}<\mathrm{Cl}$.

(ii) Down the group electron affinity decreases due to size increases. EA order: $\mathrm{S}>\mathrm{Se} \mathrm{Li}>\mathrm{Na}$.