Question

The bond order in $O_2^{-}$ ion is:

• A. 2
• B. 1
• C. 2.5
• D. 1.5

Answer 1

The correct option is D 1.5

The molecular configuration of $O_2^{-}$ is as
$\sigma 1s^2,{\sigma }^{\ast }1s^2,\sigma 2s^2,{\sigma }^{\ast }2s^2,{\sigma }^{\ast }2p_z^2,\pi 2p_y^2\approx \pi 2p_z^2,{\pi }^{\ast }2p_y^2\approx {\pi }^{\ast }{2p}_z^1$
Bond order $=\frac{N_b-N_a}{2}$
$=\frac{10-7}{2}$
$\therefore$ Bond order = 1.5