Thermal stability of carbonates increases in a group as we move from top to bottom and decreases in a period as we move from left to right. so, the correct order of thermal stability of given carbonates is:BeCO3 < MgCO3 < CaCO3 < K2CO3Be, Mg and Ca present in second group and K present in the first group.
thermal decomposition or combustion. Use water spray to keep fire-exposed containers cool. Containers may explode in the heat of a fire. Extinguishing Media: Do NOT use water directly on fire. Use dry chemical to fight fire. Use approved class D extinguishing agents or smother with dry sand, clay, or sodium bicarbonate. Autoignition Temperature: