Assertion : The oxygen molecule ( O_2 ) is attracted by an external...

The electronic configuration of $O_2$ molecule (16 electrons) according to Molecular Orbital Theory is: $\sigma_{1s}^2 \sigma_{1s}^{*2} \sigma_{2s}^2 \sigma_{2s}^{*2} \sigma_{2p_z}^2 \pi_{2p_x}^2 = \pi_{2p_y}^2 \pi_{2p_x}^{*1} = \pi_{2p_y}^{*1}$ Due to the presence of two unpaired electrons in the degenerate $\pi^{*}$ antibonding orbitals, the $O_2$ molecule is paramagnetic in nature. Paramagnetic substances are attracted by an external magnetic field. Thus, both Assertion and Reason are true and Reason is the correct explanation of Assertion. Answer: Both Assertion and Reason are true and Reason is the correct explanation of Assertion.