Question

Which of the following species exhibits the diamagnetic behaviour?

• A. $O_2^{2-}$
• B. $O_2^{+}$
• C. $O_2$
• D. $NO$

Answer 1

Answer: (A)

The correct option is $O_2^{2-}$
This species has 18 e-, which are filled in such a way that all molecular orbitals are fully filled, so diamagnetic.
$\sigma 1s^2{\sigma }^{\ast }1s^2,\sigma 2s^2{\sigma }^{\ast }2s^2,\sigma 2p_z^2,\pi 2p_x^2=\pi 2p_y^2,{\pi }^{\ast }2p_x^2={\pi }^{\ast }2p_y^2$
Hence, (1) is correct.