Question: The process that is NOT endothermic in nature is :-
$\mathrm{Ar}_{(g)}+\mathrm{e}^{-} \rightarrow \mathrm{Ar}_{(\xi)}^{-}$
$\mathrm{H}_{(\mathrm{g})}+\mathrm{e}^{-} \rightarrow \mathrm{H}_{(\mathrm{g})}^{-}$
$\mathrm{Na}_{(z)} \rightarrow \mathrm{Na}_{(z)}^{+}+\mathrm{e}$
$\mathrm{O}_{(\mathrm{g})}^{-}+\mathrm{e}^{-} \rightarrow \mathrm{O}_{(\mathrm{g})}^{2-}$
Correct Option: , 2
Solution:
$\mathrm{H}_{(\mathrm{g})}+\mathrm{e}^{-} \rightarrow \mathrm{H}^{-} \quad$ is exothermic
rest of all endothermic process.
