In Na2O2, oxygen is present as O22−, that is, as peroxide and considering molecular orbital theory for peroxide, there are no unpaired electrons. O22− = σ1s2σ*1s22s2σ*2s2σ2pz2π2px2 = π2py2π*2px2 = π*2py2 In the structure of O3, there are no unpaired electrons
In N2O, there are no unpaired electrons. N = N→O σ1s2σ*1s2σ2s2σ*2s2σ2px2π2px2 = π2py2π*2px2σ*2pz2σ3s2 In KO2, oxygen is present as O2−, that is, superoxide and considering molecular orbital theory for superoxide ion, there is one unpaired electron in π*2py orbital O2− = σ1s2σ*1s2σ2s2σ*2s2σ2pz2π2px2 = π2py2π*2px2 = π*2py′