B.O=2Nb−Na
O2−⇒σ1s2<σ∗1s2<σ2s2<σ∗2s2<σ2pz2<π2px2=π2py2<π∗2px2=π∗2py1
B.O for O2−=1.5⇒210−7=1.5
O2⇒σ1s2<σ∗1s2<σ2s2<σ∗2s2<σ2pz2<π2px2=π2py2<π∗2px1=π∗2py1
B.O for O2=2.0⇒210−6=2
O2+⇒σ1s2<σ∗1s2<σ2s2<σ∗2s2<σ2pz2<π2px2<π2py2<π∗2px1<π∗2py0
B.O for O2+=2.5⇒210−5=2.5
As per M.O.T electronic configurations
O2−<O2<O2+