Decreasing order of stability of O2,O2-,O2+ and O22- is [2015]
(4)
O2(16):KKσ2s2 σ*2s2 σ2pz2 π2px2=π2py2 π*2px1=π*2py1
Bond order=12(8-4)=2
O22-(18):KKσ2s2 σ*2s2 σ2pz2 π2px2=π2py2 π*2px2=π*2py2
Bond order = 12(8-6)=1
O2- (17):KKσ2s2 σ*2s2 σ2pz2 π2px2=π2py2 π*2px2=π*2py1
Bond order = 12(8-5)=1.5
O2+ (15):KKσ2s2 σ*2s2 σ2pz2 π2px2=π2py2 π*2px1
Bond order = 12(8-3)=2.5
As, bond order ∝ stability
The decreasing order of stability is: O2+>O2>O2->O22-