Electron affinity is positive for

Electron affinity is positive for
  1. $\mathrm{O}(\mathrm{g})+\mathrm{e}^{-} ightarrow \mathrm{O}^{-}(\mathrm{g})$
  2. $\mathrm{S}(\mathrm{g})+\mathrm{e}^{-} ightarrow \mathrm{S}^{-}(\mathrm{g})$
  3. $\mathrm{O}^{+}(\mathrm{g})+\mathrm{e}^{-} ightarrow \mathrm{O}(\mathrm{g})$
  4. $\mathrm{O}^{-}(\mathrm{g})+\mathrm{e}^{-} ightarrow \mathrm{O}^{2-}(\mathrm{g})$

Solution

When \(\mathrm{O}^{-}\)changes to \(\mathrm{O}^{2-}\), change is endothermic because \(\mathrm{O}^{-}\)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. ,

Asked in: JEE-TOPICTESTS-CHEMISTRY

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