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

$O_{(g)} + e- \longrightarrow O^{-}_{(g)} ; \Delta H^0= -142 \;kJ mol^{-1}$ $O^{-}_{(g)} + e- \longrightarrow O^{2-}_{(g)} ; \Delta H^0= 844 \;kJ mol^{-1}$ 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

Therefore, $O^{-}$ ion will tend to resist the addition of another electron