According to MO theory,

In O2 molecule, the total number of electrons = 16Electronic distribution in molecular orbital of O2=σ1s2,σ∗1s2,σ2s2,σ∗2s2,σ2px2π2py2,π2pz2 , π∗2py1,∗2pz1 Bond order in O2=12Nb−Na=12[10−6]=2.0 In O2+=σ1s2,∗1s2,σ2s2,σ∗2s2,σ2px2π2py2=π2pz2, ∗2py1 Bond order in O2+=Nb−Na2=10−52=2.5