Question

Which of the following is the least thermally stable?

• A. $L{i}_{2}C{O}_3$
• B. $MgC{O}_3$
• C. $BaC{O}_3$
• D. $BeC{O}_3$

Answer 1

The correct option is D $BeC{O}_3$

The stability of the alkaline earth metal carbonates increases with an increase in the atomic number. Thus, $BeC{O}_3$ is thermally least stable among alkaline earth metal carbonates. This is due to high polarizing power of $B{e}^{2+}$ ion and high polarisability of carbonate ion. Also, the oxide formed on decomposition of $BeC{O}_3$ is extra stable due to high lattice energy obtained by packing of small cations with small oxide ions. Due to these effects, the thermal stability of $BeC{O}_3$ is lower than that of $L{i}_{2}C{O}_3$.

Hence, option D is the correct answer.