.Why li2CO3 decomposed at a lower temperature whereas Na2CO3 at higher temp?

Li₂CO₃ is less stable than the latter, due to the large difference in sizes of the Li²⁺ and carbonate ions.

Dear Preetesh,

on going down in a group in a pereiodic table the electropositivity increases as a result the bond between Na2Co3 is more strong than Li2Co3 due to more electronegativity difference.so Li2Co3 is decomposed at a lower temperature since it requires less energy to break its bond as compared to Na2Co3.

Regards.

As we move down the alkali metal group, the electropositive character increases. This causes an increase in the stability of alkali carbonates. However, lithium carbonate is not so stable to heat. This is because lithium carbonate is covalent. 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 sodium carbonate decomposes at a high temperature.

The smaller the size of the ion, the higher the lattice energy and the greater the extent of the polarization. Li+ has a smaller size compared to Na+, hence polarizes the CO3- ion at a greater extent compared to Na+. Li2CO3 therefore requires less energy to break while Na2CO3 needs a higher energy making it more stable than Li2CO3.

Because of the covalent nature of lithium And ionic nature of sodiumThats why lithium carbonate decompose at lower temperature and sodium carbonate at higher temperature