Select the process in which the least enthalpy change is associated:

Which of the following electronic configurations will have the lowest electron affinity?

What is electron gain enthalpy?

The formation of the oxide ion,$O^{2-}_{(g)}$,from oxygen atom requires first an exothermic and then an endothermic step as shown below:
$O_{(g)} + e^- \to O^{-}_{(g)} ; \Delta_f H^{\Theta} = -141 \ kJ \ mol^{-1}$
$O^{-}_{(g)} + e^- \to O^{2-}_{(g)} ; \Delta_f H^{\Theta} = +780 \ kJ \ mol^{-1}$
Thus,the process of formation of $O^{2-}$ in gas phase is unfavourable even though $O^{2-}$ is isoelectronic with neon. It is due to the fact that,

Column-$I$ shows the electronic configuration of some elements and Column-$II$ shows the values of electron gain enthalpy. Match these values correctly. Match the electronic configuration with the electron gain enthalpy.

Column-$I$ Electronic Configuration	Column-$II$ Electron Gain Enthalpy / $kJ \ mol^{-1}$
$(A) \ 1s^2 2s^2 2p^6$	$(1) -53$
$(B) \ 1s^2 2s^2 2p^6 3s^1$	$(2) -328$
$(C) \ 1s^2 2s^2 2p^5$	$(3) -141$
$(D) \ 1s^2 2s^2 2p^4$	$(4) +53$

The process requiring absorption of energy is