Question

Among $P,S,Cl,F$, the elements with most negative and least negative electron gain enthalpy respectively, are

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

Answer 1

Answer: (C)

Generally, electron gain enthalpy increases as we move from left to right in a period and decreases as we go down in a group. But electron affinities of second period elements $(F,N)$ are less negative as compared to corresponding third period element. This is because of the small atomic size of second period elements. Hence, the correct order electron affinities is $P<S<F<Cl$ Least negative $(EA)$ Most negative $(EA)$