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

Answer

A

Explanation

Electron gain enthalpy of F is less than that of Cl because when an electron is added to F, the added electron goes to the smaller n=2 quantum level and suffers repulsion from other electrons present in this level.
In case of Cl, the added electrons goes to the larger n=3 quantum level and suffers much less repulstion from other electrons.