Question

Present a comparative account of the alkali and alkaline earth metals with respect to the following charactieristics.

(i) Tendency to form ionic / covalent compounds

(ii) Nature fo oxides and their solubility in water

(iii) Formation of oxosalts

(iv) Solubility of oxosalts.

(v) Thermal stability of oxosalts.

Answer 1

Alkali metals :

1. All alkali except Li forms ionic compounds.
2. The solubility of oxides of alkali metals increases down the group.
3. All alkali metals form oxosalts such as carbonates,
   sulphates and nitrates.
4. The solubility of carbonates and sulphates increases down the group
5. Carbonates and sulphates of Li decompose on heating while the stability of
   carbonates and sulphates of other metals increases, down the group.

Alkaline earth metals :

1. All alkaline earth metals except Be form ionic compounds.
2. The solubility of oxides of Mg, Ca, Sr and Ba increase from Mg to Ba. BeO, however, is, covalent and insoluble in water.
3. All alkaline earth metals form oxosalts such as carbonates sulphates and nitrates.
4. The solubility of carbonates and sulphates decreases down the group
5. 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.