• # question_answer Among $K{{O}_{2}},AlO_{2}^{-},\,Ba{{O}_{2}}$ and $NO_{2}^{+},$ unpaired electron is present in A)  $NO_{2}^{+}$and $Ba{{O}_{2}}$B)  $K{{O}_{2}}$ and $AlO_{2}^{-}$C)  $K{{O}_{2}}$  only           D)  $Ba{{O}_{2}}$ only

In $N{{O}_{2}}^{+}$ odd (unpaired) electron is removed. In peroxides $({{O}_{2}}^{2-})$ no unpaired electrons are present as the anti bonding pi M.O. ?S acquired one more electron each for pairing $AlO_{2}^{-}$.  containing $A{{l}^{3+}}$$(2{{s}^{2}}{{p}^{6}})$configuration and 2 oxides $({{O}^{2-}})$ ions each of which does not contain unpaired electron. Superoxide ${{O}^{2-}}$has one unpaired electron in pi anti bonding M.O.