Q.

Decreasing order of stability of O2,O2-,O2+ and O22- is          [2015]

1 O22->O2->O2>O2+  
2 O2>O2+>O22->O2-  
3 O2>O2->O2+>O22-  
4 O2+>O2>O2->O22-  

Ans.

(4)

O2(16):KKσ2s2σ*2s2σ2pz2π2px2=π2py2π*2px1=π*2py1

Bond order=12(8-4)=2

O22-(18):KKσ2s2σ*2s2σ2pz2π2px2=π2py2π*2px2=π*2py2

Bond order =  12(8-6)=1

O2- (17):KKσ2s2σ*2s2σ2pz2π2px2=π2py2π*2px2=π*2py1

Bond order = 12(8-5)=1.5

O2+ (15):KKσ2s2σ*2s2σ2pz2π2px2=π2py2π*2px1

Bond order = 12(8-3)=2.5

As, bond order  stability

The decreasing order of stability is: O2+>O2>O2->O22-