The formation of the oxide ion , from oxygen atom requires first an exothermic and then an endothermic step as shown below: Thus process of formation of in gas phase is unfavourable even though is isoelectronic with neon. It is due to the fact that

Question

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

$O_{(g)} + e^{-} \to {O^{-}}_{(g)}; Δ_{1} H ° = - 141 k J m o l^{- 1}$

${O^{-}}_{(g)} + e^{-} \to {O^{2 -}}_{(g)}, Δ_{2} H ° = + 780 k J m o l^{- 1}$

Thus 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

Smart Achievers · Accepted Answer

(1)

2nd electron affinity is positive

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