Why are lithium salts commonly hydrated and those of other alkali ions usually anhydrous?



Lithium salts are commonly hydrated like Licl…2${{H}_{2}}$0 whereas other alkali ions are usually anhydrous.
The hydration enthalpy of Li+ ion is maximum among the alkali metal ions. Becasue of its ex-tremely small size, Li+ ion is maximum hydrated and therefore, the effective size of Li+ in aqueous solution is the largest. The hydration enthalpy decreases with increase in ionic size.
Li+ > Na+ > K+ > Rb+ > Cs+
Therefore, the ions of other alkali metals are usually anhydrous.