Chemical Bonding and Molecular Structure Part 2

Those species which have unpaired electrons are called paramagnetic species.And those species which have no unpaired electrons are called diamagnetic species.$\mathrm{B}_2$ has 10 electrons.Molecular orbital configuration of $\mathrm{B}_2$ is$\sigma_{1s^2} \sigma_{1s^2}^* \sigma_{2s^2} \sigma_{2s^2}^* \pi_{2p_x^1} = \pi_{2p_y^1}$Here two unpaired electrons present. So it is paramagnetic.$\mathrm{O}_2^{2-}$ has 18 electrons. Moleculer orbital configuration of $\mathrm{O}_2^{2-}$ is$\sigma_{1s^2} \sigma_{1s^2}^* \sigma_{2s^2} \sigma_{2s^2}^* \sigma_{2p_z^2} \pi_{2p_x^2} = \pi_{2p_y^2} \pi_{2p_x^2}^* = \pi_{2p_y^2}^*$Here is no unpaired electron so it is diamagnetic.$\mathrm{O}_2^{+}$has 15 electrons.Moleculer orbital configuration of $\mathrm{O}_2^{+}$is$\sigma_{1s^2} \sigma_{1s^2}^* \sigma_{2s^2} \sigma_{2s^2}^* \sigma_{2p_z^2} \pi_{2p_x^2} = \pi_{2p_y^2} \pi_{2p_x^1}^* = \pi_{2p_y^0}^*$ Here 1 unpaired electron present, so it is paramagnetic.$\mathrm{C}_2$ has 12 electrons.Moleculer orbital configuration of $\mathrm{C}_2$$= \sigma_{1s^2} \sigma_{1s^2}^* \sigma_{2s^2} \sigma_{2s^2}^* \pi_{2p_x^2} = \pi_{2p_y^2}$Here no unpaired electron present, so it is diamagnetic.$\mathrm{C}_2^{-}$has 13 electrons. Moleculer orbital configuration of $\mathrm{C}_2^{-}$is$\sigma_{1s^2} \sigma_{1s^2}^* \sigma_{2s^2} \sigma_{2s^2}^* \pi_{2p_x^2} = \pi_{2p_y^2} \sigma_{2p_z^1}$Here 1 unpaired electron present, so it is paramagnetic.$\mathrm{Li}_2$ has 6 electrons.$\mathrm{Li}_2 = \sigma_{1s^2} \sigma_{1s^2}^* \sigma_{2s^2}$Here no unpaired electron present, so it is diamagnetic.Configuration of $\mathrm{He}_2^{+}$(3 electrons) is $= \sigma_{1s^2} \sigma_{1s^1}^*$ Here 1 unpaired electron present, so it is paramagnetic.