Question

Present a comparative account of the alkali and alkaline earth metals with respect to the following characteristics:

(i) Tendency to form ionic/covalent compounds

(ii) Nature of oxides and their solubility in water

(iii) Formation of oxosalts

(iv) Solubility of oxosalts

(v) Thermal stability of oxosalts

Answer 1

Alkali metals	Alkaline earth metals
(i) All alkali metals except Li form ionic compounds.	(i) All alkaline earth metals except Be form ionic compounds.
(ii) The solubility of oxides of al­kali metals increases down the group. The basic character of the ox­ides increases down the group	(ii) The solubility of oxides of Mg, – Ca, Sr and Ba increases from Mg to Ba. BeO, however, is covalent and insoluble in water. The basic character of oxides in­creases from MgO to BaO. BeO is, however, amphoteric.
(iii) All alkali metals form oxo salts such as carbonates, sul­phates and nitrates.	(iii) All alkaline earth metals form oxo salts such as carbonates, sulphates and nitrates.
(iv) Solubility of carbonates and sul­phates increases down the group.	(iv) Solubility of carbonates and sul­phates decreases down the group.
(v) Carbonates and sulphates of Li decompose on heating while the stability, of carbonates and sulphates of other metals in­creases down the group.	(v) The carbonates and sulphates of alkaline earth metals all decom­pose on heating but the tempera­ture of their decomposition in­creases down the group, i.e., their thermal stability increases.