The negative value of electron gain enthalpy is less for fluorine than for chlorine . Why?

Explanation

Atomic size of fluorine is less than chlorine. Hence , the interelectronic repulsion, i.e., the electrons already preset in `F` and the electron to be added is much more than the `Ci` atom. Hence, the incoming electron is accepted with diffculty in `F`. The energy released during formation of `F_((g))^(Theta)` from `F_((g))` is less than that of formation of `Cl^(Theta)` from `Cl_((g))`. Thus, negative gain enthalpy of `F` is lower than that of `Cl`.