Question

Which of the following molecules\ions does not contain unpaired electrons?

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

Answer 1

The correct option is C $O_2^{2-}$

The molecular orbital diagram of $O_2^{-2},{\pi }^{\ast }2Px$ and ${\pi }^{\ast }2Py$ molecular orbitals are completely filled , which are partially filled in $O_2$. These are no unpaired electrons. So, $O_2^{-2}$ does not contain unpaired electrons.