Alkali and alkaline earth metals along with hydrogen and helium constitute s-block elements . They have low ionization enthalpies and hence exhibit characteristic flame colouration . They have highly negative electrode potentials and hence are strong reducing agents . Their solutions in liquid ammonia are conducting and also act as strong reducing agents than hydrogen , they are usually prepared by electrolysis of their fused chlorides . Their oxides are basic and the basic strength increases down the group . The solubility of carbonates and sulphates of alkali and alkaline earth metals show opposite trends . The carbonates of alkaline earth metals and lithium carbonate decompose on heating while the carbonates of other alkali metals do not decompose on heating . The bicarbonates of both alkali and alkaline earth metals on heating give carbonates . The basic character of the oxides , MgO , SrO , K_(2)O , NiO and Cs_(2)O increases in the order :