Li(I) is the smallest alkali metal ion, which allows it to easily polarize water molecules. Li salts are linked to the crystallization water. Each mole of lithium chloride contains two water molecules. Because the other alkali metals are larger, they have a harder time polarizing water molecules. As a result, the salts do not bond to the crystallization water.
Final answer: Hence, as lithium is the smallest alkali metal it can easily be hydrated.