Metal carbonates decompose on heating to give metal oxide and carbon dioxide. Which of the metal carbonates is most stable thermally?

1. ${\mathrm{MgCO}}_{3}$

2. ${\mathrm{CaCO}}_{3}$

3. ${\mathrm{SrCO}}_{3}$

4. ${\mathrm{BaCO}}_{3}$

Hint:  Down the group thermal stability increases
${\mathrm{BaCO}}_{3}$ thermally most stable because thermal stability increases with increasing cationic size. ${\mathrm{Ba}}^{2+}$ cation has the maximum size among all given cations, that is,