# The pairs of species of oxygen and their magnetic behaviour are noted below. Whichof the follow ing presents the correct description?

As we learnt in

Magnetic behaviour of molecule -

If  all the molecular orbitals in a molecule are doubly occupied, the substance is diamagnetic

- wherein

However if one or more molecular orbital are singly occupied it is paramagnetic e.g. O2

Electronic configuration of $O_{2}$ molecule

$\sigma_{2s}^{2}\;\sigma_{2s}^{*2} \; \sigma_{2p}^{2}\; \pi_{2px}^{2}\; \pi_{2py}^{2}\; \pi_{2px}^{*1}\; \pi_{2py}^{*1}$

Since there are 2 unpaired electrons in $2p_x$ & $2p_y$ degenerate orbitals, so, $O_{2}$ is paramagnetic.

Similarly, for $O_{2}^{*}$ molecule, we have

$\sigma_{2s}^{2}\;\sigma_{2s}^{*} \; \sigma_{2p}^{2}\; \pi_{2p}^{2}\; \pi_{2py}^{2}\; \pi_{2px}^{*1}$

Since, there is 1 unpaired electron in $2p_x$ orbital,

$\therefore$ $O_{2}^{+}$ is paramagnetic.

Option 1)

$O^{-}_{2}, O_{2}^{2-}$      - Both diamagnetic

This option is incorrect.

Option 2)

$O^{+}, O_{2}^{2-}$      -  Both paramagnetic

This option is incorrect.

Option 3)

$O_{2}^{+}, O_{2}$     - Both paramagnetic

This option is correct.

Option 4)

$O, O_{2}^{2-}$ -  Both paramagnetic

This option is incorrect.

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