The species having an O-O bond and O in an oxidation state of −
1
2
are super oxides and is represented as O2−. Usually, these are formed by active metals such as KO2,RbO2andCsO2. For the salts of larger anions (like O2−), lattice energy increases in a group. Since, lattice energy is the driving force for the formation of an ionic compound and its stability, the stability of the superoxides from 'K' to 'Cs' also increases.