Assertion: Electron gain enthalpy becomes less negative as we go down a group. Reason: The size of the atom increases on going down the group and the added electron would be farther from the nucleus.

Electron affinity is the energy released when an electron is added to a neutral atom. As we go down from top to bottom in a group, the electron gain enthalpy becomes less negative because as we go down in a group, electrons are added in new principal quantum numbers which result in an increase in the atomic radius and decrease in the effective nuclear force on the valence electrons. So, metallic property increases down the group, and hence, electron gain enthalpy becomes less negative as we down the group. Therefore, both assertion and reason are correct and the given reason is the correct exp