Why lithium carbonate decomposed at low temperature but sodium carbonate at high temperature?

Lithium carbonate decomposes at lower temperatures due to its relatively weaker ionic bonds and lower lattice energy compared to sodium carbonate. The smaller lithium ion leads to stronger polarizing effects, making the compound less stable. In contrast, sodium carbonate has stronger ionic bonds and higher lattice energy, requiring higher temperatures to overcome these forces and initiate decomposition. This difference in thermal stability is primarily due to the varying ionic sizes and charges of lithium and sodium.