Question

Sum of antibonding $\pi$ Electrons$\left({\pi }^{\ast }\right)$ in species $O_2,O_2^{-}$ and $O_2^{2-}$ are

Answer 1

Molecular orbitals electronic configuration of these species are :

• $O^{-2}\left(17e^{-}\right)=\sigma 1s^2{\sigma }^{\ast }1s2,\sigma 2s^2{\sigma }^{\ast }2s^2,\sigma 2p_x^2,\pi 2p_y^2,\pi 2p_z^2,{\pi }^{\ast }2p_y^2{\pi }^{\ast }2p_z^1$

• $O_2\left(16e^{-}\right)=\sigma 1s^2{\sigma }^{\ast }1s2,\sigma 2s^2{\sigma }^{\ast }2s^2,\sigma 2p_x^2,\pi 2p_y^2,\pi 2p_z^2,{\pi }^{\ast }2p_y^1{\pi }^{\ast }2p_z^1$

• $O_2^{-2}\left(18e^{-}\right)=\sigma 1s^2{\sigma }^{\ast }1s2,\sigma 2s^2{\sigma }^{\ast }2s^2,\sigma 2p_x^2,\pi 2p_y^2,\pi 2p_z^2,{\pi }^{\ast }2p_y^2{\pi }^{\ast }2p_z^2$

Hence, the number of antibonding electrons are 7,6 and 8 respectively and sum is $7+6+8=21$