Question

Name the factors that affect the thermal stability of alkali metal salts. Explain the stability trend observed in case of nitrates of these metals.

Answer 1

The thermal stability of a substance depends heavily on the structure of the substance which, in turn, is dependent on the bonds between atoms that hold that structure together.
Group 1 nitrates decompose to form products: MeNO2 + O2
Going down Groups 1, nitrates become more stable. Higher temperatures are needed to decompose them. Cations (positively charged ions) can affect anions such as NO3-. They can lower the energy needed to break a N–O bond.
This effect increases:
• the smaller the cation
• the greater the cation’s charge.
The small positive ions at the top of the Group polarise the nitrate more than the larger positive ions at the bottom.