Discuss the trend of the following: Thermal stability of carbonates of Group 2 elements.

All the alkaline earth metals form carbonates (MCO₃). All these carbonates decompose on heating to give CO₂ and metal oxide. The thermal stability; of these carbonates increases down the group, i.e., from Be to Ba,
BeCO₃ < MgCO₃ < CaCO₃ < SrCO₃ < BaCO₃
BeCO₃ is unstable to the extent that it is stable only in atmosphere of CO₂. It however shows reversible decomposition in closed container 

BeCO₃ ⇌ BeO + CO₂

Hence, more is the stability of oxide formed, less will be stability of carbonates. Stability of oxides decreases down the group. Since beryllium oxide is high stable, it makes BeCO₃ unstable.