JEE Main levelSingle correct optionDifficulty 2 of 3pt135
The electron gain enthalpy of fluorine is less negative than that of chlorine mainly because
Afluorine has a larger atomic radius than chlorine
Bthe added electron enters a very small 2p subshell where inter-electronic repulsion is large
Cfluorine has a lower nuclear charge than chlorine
Dfluorine does not need one more electron to complete its octet
Answer: B
F is 2s22p5; its compact 2p orbitals make the added electron experience strong repulsion from the existing seven electrons. In Cl the 3p subshell is larger, so the repulsion is much less, giving a more negative value.