(A) Molecular orbital configuration of O22− (18 electrons) is σ1s2σ1s2*σ2s2σ2s2*σ2pz2π2px2=π2py2π2px2*=π2py2* So O22− has no unpaired electrons. (B) Molecular orbital configuration of B2 ( 10 electrons) is σ1s2σ1s2*σ2s2σ2s2*π2px1=π2py1 Here in B2,2 unpaired electrons present. (C) Molecular orbital configuration of N2+(13 electrons) =σ1s2σ1s2*σ2s2σ2s2*π2px2=π2py2σ2pz1 Here in N2+,1 unpaired electron present. (D) Molecular orbital configuration of O2 ( 16 electrons) is So O2 has 2 unpaired electrons. σ1s2σ1s2*σ2s2σ2s2*σ2pz2π2px2=π2py2π2px1*=π2py1* So O2 has 2 unpaired electrons.