Question

Which of the following molecules /ions do not contain unpaired electrons?

• A. $N_2^{+}$
• B. $O_2$
• C. $O_2^{2-}$
• D. $B_2$

Answer 1

Answer: (C)

$O_2^{2-}$

Molecular orbital electronic configaration of $O_2^{-2}$

$O_2^{-2}=\sigma 1s^2,\sigma \ast 1s^2,\sigma 2s^2,\sigma \ast 2s^2,\sigma 2p{x}^2,\pi 2p{y}^2=\pi 2p{z}^2,\pi \ast 2p{y}^2=\pi \ast 2p{z}^2,\sigma \ast 2p{x}^0$.

So there are no unpaired electrobns in the molecular orbitals of $O_2^{-2}$.

Hence option C is corrrect.