Question

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

Answer 1

Hint: As lithium compounds are also known as the lithium salt. Anhydrous literally means “no water”. In chemistry, the substance without water is labeled as anhydrous. And a hydration reaction is a chemical reaction in which a substance combines with water. In organic. chemistry, water is added to an unsaturated substrate, which is usually an alkene or an alkyne.

Complete step by step answer:
As we know that, the atomic number of lithium is ${\text{3}}$ and the electronic configuration of lithium is $\left[ {He} \right]2{s^2}$ that is $1{s^2}2s.$ Lithium is the smallest in size among all the alkali metals. Due to which, $L{i^ + }$ ions can raise water molecules more easily than the other alkali metals, As a result, water molecules water molecules more easily than the other alkali metals. As a result, water molecules are attached to lithium salts as water of crystallization. The lithium chloride contains water molecules per mole of ${\text{LiCl}}$.

Hence lithium salts such as trihydrated lithium chloride are mostly hydrated. And as the size of the ion increases, their polarizing power decreases. Moreover, the other alkali metals being bigger in size cannot polarize water molecules more easily. Hence their salts do not get bonded to the water of crystallization. Therefore, other alkali metal ions usually form anhydrous salts. Just because of high charge density among alkali metals, ${\text{L}}{{\text{i}}^{\text{ + }}}$ can polarize water molecules more easily than the other alkali metal ions.

Note: Since the size of $L{i^ + }$ is the smallest among the alkali metal ions, therefore the charge density is very high and hence it attracts the water molecules more strongly than any other alkali metal cation.