The distribution of electrons in MOs is as follows : N2+(electrons 13)⇒KKσ2s2σ*2s2σ2pz2π2px2=π2py1 ⇒KKσ2s2σ2s2σ2px2⇒O2( electron 16) π2px2=π2py2π*2px1=π*2py1 ⇒KKσ2s2σ*2s2σ2px2⇒O22−( electron 18 ) π2px2=π2py2π*2px2=π*2py2 B2( electrons 10)⇒KKσ2s2σ*2s2σ2px2 KKσ2s2σ*2s2π2px1=π2py1 Only O22− does not contain any unpaired electron.