The formation of the oxide ion $O^{2-}_{(g)}$ requires first an exothermic and then an endothermic step, as shown below:

Question

$O_{(g)} + e- \longrightarrow O^{-}_{(g)} ; \Delta H^0= -142 \;kJ mol^{-1}$ $O^{-}_{(g)} + e- \longrightarrow O^{2-}_{(g)} ; \Delta H^0= 844 \;kJ mol^{-1}$ This is because of which of the following reasons?

(A) $O^{-}$ ion is comparatively larger size than the oxygen atom
(A) $O^{-}$ ion is comparatively larger size than the oxygen atom
(C) Oxygen is more electrogenative
(D) Oxygen has high electron affinity