Discuss the trend of the following:

(i) The thermal stability of the carbonates increases with increasing cationic size. The more stable the oxide of an alkaline earth metal, the less stable is the carbonate of

the same. Hence BeCO3 is highly unstable as BeO is stable.

(ii) Alkali metals form oxides with oxygen and give metal oxides. The oxides will be basic except BeO because BeO is amphoteric. hey also react with water to form

sparingly soluble hydroxides. As the size of the cations increase BeO and MgO have the highest lattice energy and they are insoluble in water.