In all cases, for a particular set of e . g . Group 1 or Group 2 compounds, the thermal stability increases down the group as the ionic radius of the cation increases, and its polarising power decreases.

Group 1 compounds tend to be more thermally stable than group 2 compounds because the cation has a smaller charge and a larger ionic radius,

and so a lower polarising power, particularly when adjacent metals on the same period are compared. Hence, the order of increasing thermal stability of and is