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

Answers (1)

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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