Question

Thermally least stable carbonate among the following is

• A. $SrC{O}_3$
• B. $MgC{O}_3$
• C. $CaC{O}_3$
• D. $BaC{O}_3$

Answer 1

The correct option is B $MgC{O}_3$

As the size of $2^{nd}$ group cation increases down the group, its polarizing power decreases. So, covalent character in metal carbonate decreases or ionic character increases. As a result, on moving down the group in Alkaline earth metals, the thermal stability of carbonate increases.

Carbonate	$MgC{O}_3$	$CaC{O}_3$	$SrC{O}_3$	$BaC{O}_3$
Decomposition temperature (K)	813	1173	1563	1633