By the use of molecular orbital consideration, account for the fact that oxygen is paramagnetic.

Explanation

Electronic configuration of molecular orbitals of `O_2` is `( sigma 1s)^2 ( sigma^* 1s)^2 ( sigma 2s)^2 ( sigma ^* 2s)^2 ( sigma 2p_z)^(2 ( pi 2p_x)^2 ( pi 2p_y)^2 ( pi ^* 2p_x)^(1) ( pi ^* 2p_z)^1`
The last two electrons are in `pi^* 2p_x ` and `pi ^* 2p_y ` anti bonding orbitals so as to maximise pi electrons in accordance with Hund.s rule. These two unpaired electrons conferí phramagnetism in Oxygen.