The correct order of increasing thermal stability of K ₂ CO ₃, MgCO ₃, CaCO ₃ and BeCO ₃ is:

Step-by-step solution

The basicity of metal hydroxides increases down the group from Be to Ba , so, the thermal stability of their carbonates also increases in the same order. Also, group 1 compound are more thermally stable than group 2 because their hydroxide are much basic than group 2 hydroxides. BeCO ₃ < MgCO ₃ < CaCO ₃ < K ₂ CO ₃