Question

Electron affinity is positive, when :

• A. $O$ changes to $O^{-}$
• B. $O^{-}$ changes into $O^{2-}$
• C. $O$ changes into $O^{+}$
• D. electron \ affinity \ is \ always \ negative

Answer 1

The correct option is B $O^{-}$ changes into $O^{2-}$

When $O^{-}$ changes to $O^{2-}$, change is endothermic because $O^{-}$ repels the incoming electron due to similar charge, hence, it needs energy to accept the electron. The second electron affinity of oxygen is particularly high because the electron is being forced into a small, very electron-dense space. So, electron affinity is positive