UPSEE Solved Model Paper 5

Thermal stability of carbonates increases in a group as we move from top to bottom and decreases in a period as we move from left to right.
Be, Mg and Ca are second group elements and K present in the first group.
So, the correct order of thermal stability of given carbonates is:
BeCO3 < MgCO3 < CaCO3 < K2CO3