Compare the solubility and thermal stability of the following compounds of the alkali metals with those of the alkaline earth metals. (a) Nitrates (b) Carbonates (c) Sulphates.

Carbonates: -i. Solubility: - Carbonates of alkali metals are soluble in water except Li₂CO₃.ii. Thermal stability: - The carbonates of alkali metals except lithium carbonate are stable towards heat. The carbonates of alkaline earth metals and Lithium carbonate decompose on heating to form oxides with the evolution of CO₂.
Li₂CO₃→ Li₂O + CO₂
MgCO₃→ MgO + CO₂
Nitrates:-i. Solubility:-Nitrates of both alkali and alkaline metals are soluble in water due to more hydration energy than lattice energy.ii. Thermal Stability:-Nitrates of alkali metal except Lithium nitrate on heating forms nitrites with the evolution of oxygen.
NaNO₃→ Na₂O + O₂.
LiNO₃ and nitrates of alkaline earth metals on heating form their respective oxides NO₂ and O₂.
2LiNO₃ → Li₂O + 2NO₂ + O₂
2Ca(NO₃)₂ → 2CaO + 4NO₂ + O₂Sulphates: -
i. Solubility: - Sulphates of alkali metals are generally soluble in water except Li₂SO₄.ii. Thermal stability: - The Sulphates of both alkali and alkaline earth metals are thermally stable.