Question -
Answer -
Aswe move down the alkali metal group, the electropositive character increases.This causes an increase in the stability of alkali carbonates. However, lithiumcarbonate is not so stable to heat. This is because lithium carbonate iscovalent. Lithium ion, being very small in size, polarizes a large carbonate ion,leading to the formation of more stable lithium oxide.
Therefore,lithium carbonate decomposes at a low temperature while a stable sodiumcarbonate decomposes at a high temperature.