3.20 Which of the following pairs of elements would have a more negative electron gain enthalpy?
(ii) F or Cl
The electron gain enthalpy value of Cl is more negative than that of F .
This is because of the reason for the smaller size of F due to its small size, the electron repulsions in the relatively compact 2p-subshell are comparatively large and hence the attraction for an incoming electron is less as in the case of Cl.