Chemical Bonding and Molecular Structure Part 1

Those species which have unpaired electrons are called paramagnetic species. And those species which have no unpaired electrons are called diamagnetic species. (a) $\mathrm{O}_2^{2-}$ has 18 electrons. Moleculer orbital configuration of $\mathrm{O}_2^{2-}$ is $\sigma_{1 s^{2}} \sigma_{1 s^{2}}^{*} \sigma_{2 s^{2}} \sigma_{2 s^{2}}^{*} \sigma_{2 p_z^{2}} \pi_{2 p_x^{2}} = \pi_{2 p_y^{2}} \pi_{2 p_x^{2}}^{*} = \pi_{2 p_y^{2}}^{*}$ Here is no unpaired electron so it is diamagnetic. (b) NO has 15 electrons. Moleculer orbital configuration of NO is $\sigma_{1 s^{2}} \sigma_{1 s^{2}}^{*} \sigma_{2 s^{2}} \sigma_{2 s^{2}}^{*} \sigma_{2 p_z^{2}} \pi_{2 p_z^{2}} = \pi_{2 p_y^{2}} \pi_{2 p_x^{1}}^{*} = \pi_{2 p_y^{0}}^{*}$ Here is 1 unpaired electron, So it is Paramagnetic. (c) $\mathrm{O}_2$ has 16 electrons.Moleculer orbital configuration of $\mathrm{O}_2$ is $\sigma_{1 s^{2}} \sigma_{1 s^{2}}^{*} \sigma_{2 s^{2}} \sigma_{2 s^{2}}^{*} \sigma_{2 p_z^{2}} \pi_{2 p_z^{2}} = \pi_{2 p_y^{2}} \pi_{2 p_x^{1}}^{*} = \pi_{2 p_y^{1}}^{*}$ Here 2 unpaired electron present, so it is paramagnetic. (d) $\mathrm{O}_2^{+}$has 15 electrons. Moleculer orbital configuration of $\mathrm{O}_2^{+}$is $\sigma_{1 s^{2}} \sigma_{1 s^{2}}^{*} \sigma_{2 s^{2}} \sigma_{2 s^{2}}^{*} \sigma_{2 p_z^{2}} \pi_{2 p_z^{2}} = \pi_{2 p_y^{2}} \pi_{2 p_x^{1}}^{*} = \pi_{2 p_y^{0}}^{*}$ Here 1 unpaired electron present, so it is paramagnetic.