(i). All the alkali metals on exposure to air burn vigorously, forming oxides on the surface of the metals.
(ii). Lithium forms only monoxide, sodium forms the monoxide and peroxide and the other elements form monoxide, peroxide and superoxides.
4Li + O2 → 2Li2O (Lithium monoxide)
2Na + O3 → Na2O2 (Sodium peroxide)
K + O3 → KO2 (Potassium superoxide)