Question

Which of the following molecules or 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 $O_2^{2-}$

(a) $N_2^{+}:\left({\sigma }_{1s}{)}^2\right({\sigma }_{1s}^{\ast }{)}^2\left({\sigma }_{2s}{)}^2\right({\sigma }_{2s}^{\ast }{)}^2\left({\pi }_{2px}{)}^2\right({\pi }_{2py}{)}^2({\sigma }_{2pz}{)}^1$

(b) $O_2:\left({\sigma }_{1s}{)}^2\right({\sigma }_{1s}^{\ast }{)}^2\left({\sigma }_{2s}{)}^2\right({\sigma }_{2s}^{\ast }{)}^2\left({\sigma }_{2pz}{)}^2\right({\pi }_{2px}{)}^2\left({\pi }_{2py}{)}^2\right({\pi }_{2px}^{\ast }{)}^1({\pi }_{2py}^{\ast }{)}^1$

(c) $O_2^{2-}:\left({\sigma }_{1s}{)}^2\right({\sigma }_{1s}^{\ast }{)}^2\left({\sigma }_{2s}{)}^2\right({\sigma }_{2s}^{\ast }{)}^2\left({\sigma }_{2pz}{)}^2\right({\pi }_{2px}{)}^2\left({\pi }_{2py}{)}^2\right({\pi }_{2px}^{\ast }{)}^2({\pi }_{2py}^{\ast }{)}^2$.

(d) $B_2:\left({\sigma }_{1s}{)}^2\right({\sigma }_{1s}^{\ast }{)}^2\left({\sigma }_{2s}{)}^2\right({\sigma }_{2s}^{\ast }{)}^2\left({\pi }_{2px}{)}^1\right({\pi }_{2py}{)}^1$.