Explain why the electron gain enthalpy of fluorine is less negative than that of chlorine.

(N/A) The electron gain enthalpy of fluorine is less negative than that of chlorine due to its small atomic size.
In fluorine,the incoming electron experiences significant inter-electronic repulsion because the $2p$ orbitals are compact.
In contrast,chlorine has a larger atomic size and the incoming electron enters the $3p$ orbital,which has more space available.
This results in less inter-electronic repulsion in chlorine,making the process more exothermic and leading to a more negative electron gain enthalpy compared to fluorine.