Question

Among $KO_2$, $AlO_2^-$ , $BaO_2$ and $NO_2^+$, unpaired electron is present in

• A. $NO_2^+$ and $BaO_2$
• B. $KO_2$, and $AlO_2^-$
• C. Only $KO_2$
• D. Only $BaO_2$

Answer 1

Answer: (C)

Molecular orbital electronic configuration are

Has one unpaired electron in $\overset{*} {\pi}2 p$ orbital.
$AlO _{2}^{-}$has both oxygen in $O ^{2-}$ state, therefore, no unpaired electron is present. $BaO _{2}\left( O _{2}^{2-}\right)$

Has no unpaired electron.
$N O_{2}^{+}$has $\left[O=\overset{+}{N}=O\right]$ bonding, hence no unpaired electron.