The peroxide and oxides of alkali metals are colourless when pure. Superoxides are paramagnetic while peroxides are diamagnetic. Electronic configuration of O22− (peroxide) (σ1s2)(σ*1s2)(σ2s2)(σ*2s2)(σ2pz2)(π2px2π2py2)(π*2px2π*2py2) Electronic configuration of O2− (σ1s2)(σ*1s2)(σ2s2)(σ*2s2)(σ2pz2)(π2px2‌‌π2py2)(π*2px2π*2py1) superoxide is paramagnetic due 1 unpaired electron.