Question

Li₂CO₃ decomposes readily whereas other carbonates are not. Why?

Answer 1

The carbonates (M₂CO₃ ) of alkali metals are remarkably more stable up to 1270 K above which they first melt and then decompose to form their oxides, whereas Li₂CO₃ is less stable and Li₂CO₃ + ∆ → Li₂O + CO₂↑ 

This is due to the large size difference between Li and \(CO_3^{2-}\) which makes the crystal lattice unstable.