Which one of the alkaline earth metal carbonates is thermally the most stable?

Thermal stability increases with the increase in the size of the cation present in the carbonate. The increasing order of the cationic size of the given alkaline earth metals is

Mg < Ca < Sr < Ba

Hence, the increasing order of the thermal stability of the given alkaline earth metal carbonates is

$\mathrm{MgCO}_{3}<\mathrm{CaCO}_{3}<\mathrm{SrCO}_{3}<\mathrm{BaCO}_{3}$