Those species which have unpaired electrons are called paramagnetic species. And those species which have no unpaired electrons are called diamagnetic species. B2 has 10 electrons. Molecular orbital configuration of B2 is σ1s2σ1s2*σ2s2σ2s2*π2px1=π2py1 Here two unpaired electrons present. So it is paramagnetic. O22− has 18 electrons. Moleculer orbital configuration of O22− is σ1s2σ1s2*σ2s2σ2s2*σ2pz2π2px2=π2py2π2px2*=π2py2* Here is no unpaired electron so it is diamagnetic. O2+has 15 electrons. Moleculer orbital configuration of O2+is σ1s2σ1s2*σ2s2σ2s2*σ2pz2π2px2=π2py2π2px1*=π2py0* Here 1 unpaired electron present, so it is paramagnetic. C2 has 12 electrons. Moleculer orbital configuration of C2 =σ1s2σ1s2*σ2s2σ2s2*π2px2=π2py2 Here no unpaired electron present, so it is diamagnetic. C2−has 13 electrons.
Moleculer orbital configuration of C2−is σ1s2σ1s2*σ2s2σ2s2*π2px2=π2py2σ2pz1 Here 1 unpaired electron present, so it is paramagnetic. Li2 has 6 electrons. Li2=σ1s2σ1s2*σ2s2 Here no unpaired electron present, so it is diamagnetic. Configuration of He2+(3 electrons) is =σ1s2σ1s1*
Here 1 unpaired electron present, so it is paramagnetic.