Question

Electron affinity is positive, when

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

Answer 1

Answer: (B)

$O^{-}$ changes into $O^{2-}$

Answer 2

When $O ^{-}$, changes into $O ^{2-}$, change is endothermic because $O ^{-}$repels the incoming electron due to similar charge, hence it needs energy to accept the electron. So, electron affinity is positive.