Why is `Li_(2)CO_(3)` decomposed at a lower temperature whereas `Na_(2)CO_(3)` at higher temperature?

Explanation

Lithium is less electropositive than sodium and there-fore, carbonate of lithium is less stable than that of sodium. `Li_(2)CO_(3)` is not so stable to heat and therefor, decomposes at lower temperature. This is because lithium being very small in size polarises a large `CO_(3)^(2-)` ion leading to the formation of `Li_(2)O` and `CO_(2)`. On the other hand, `Na_(2)CO_(3)` is very stable and decomposes at higher temperature.