. Assertion: K, Rb and Cs form superoxides.
Reason :The stability of the superoxides increases from ‘K’ to ‘Cs’ due to decrease in lattice energy.
Answer ||| (c)
Solution ||| Superoxides are the species having an O—O bond and O in an oxidation state of -1/2 (superoxide ion is o2-). Usually these are formed by active metals such as KO2, RbO2 and CsO2. 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.