Question

Which of the following will have the most negative electron gain enthalpy and which
the least negative? P, S, Cl, F, N, Br, I. Explain.

Answer 1

Electron gain enthalpy is small for nitrogen and highest for chlorine.
Electron gain enthalpy increases when we move from left to right and decreases when it moves down the group. But fluorine due to its small size experiences electron electron repulsion and has lesser electron gain enthalpy. That is why chlorine has highest.