Decreasing order of stability of O2,O2-,O2+and O22- is

O2(16):KKσ2 s2σ*2 s2σ2pz2π2px2=π2py2π*2px1=π*2py1 Bond order =12(8-4)=2O22-(18):KKσ2s2σ*2s2σ2pz2π2px2=π2py2π*2px2=π*2py2 Bond order =12(8-6)=1O2-(17):KKσ2s2σ*2s2σ2pz2π2px2=π2py2π*2px2=π*2py1 Bond order =12(8-5)=1.5O2+(15):KKσ2 s2σ*2 s2σ2pz2π2px2=π2py2π*2px1 Bond order =12(8-3)=2.5 As, bond order ∝ stability The decreasing order of stability isO2+>O2>O2->O22-