Which of the following will have the most negative electron gain enthalpy and which the least negative? `P, S, Cl, F`. Explain your answer.

Options

A. `P, CI`
B. `CI, F`
C. `CI, S`
D. `CI, P`

Answer

D

Explanation

In chlorine, the addition of additional electron to larger `3p`-subsheel experiences less electron-electron repulsion than smaller `2p`-subshell of fluorine. Phosphours has very low electron affinity because there is high electron repulsion when the incoming electron enters an orbital that is already half filled.