Compare the solubility and thermal stability of the given compounds of the alkali metals with those of the alkaline earth metals.
Carbonates.

Explanation

Carbonates: (a) Except `Li_2CO_3`, other carbonates of alkali metals readily dissolve in water. However, carbonates of alkaline earth metals are practically insoluble in water. Their solubilities decrease on moving down the group. So, `BeCO_3` is sparingly soluble in water while `BaCO_3` is insoluble in water. (b) Carbonates of alkali metals except `Li_2CO_3` are stable and do not decompose on heating, but carbonates of alkaline earth metals decompose on heating to give metal oxide and carbon dioxide.
`MCO_3 overset(Delta)to MO + CO_2 uarr` (M Be, Mg, Ca, Sr, Ba)
Thermal stability of the carbonates increases down the group. Like `MgCO_3 overset(Delta)to Li_2O + CO_2 uarr`