The thermal stability of alkaline earth metal carbonates () increases down the group (). What is the — s Block Elements Chemistry Question

💡 Solution & Explanation

According to Fajans' rules, a smaller cation (like $Be^{2+}$) has high polarizing power. It heavily distorts the electron cloud of the large polyatomic $CO_3^{2-}$ ion, weakening the C-O bond and facilitating decomposition into $MO$ and $CO_2$. Larger cations have lower polarizing power, thus increasing thermal stability.