The set containing the elements with positive electron gain enthalpies is

The electron affinity values (in $kJ \ mol^{-1}$) for halogens $X, Y,$ and $Z$ are $-349, -333,$ and $-325$ respectively. Therefore,$X, Y,$ and $Z$ are respectively which of the following?

Which of the following processes involves absorption of energy?

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

The correct order of electron affinity of $B, C, N, O$ is

The electron affinity for the inert gases is