Question

Ionic mobility of which of the following alkali metal ions is lowest when aqueous solution of their salts are put under an electric field?

• A. K
• B. Rb
• C. Li
• D. Na

Answer 1

The correct option is C Li

As we go down the group, the size of the ionic radius increases. This implies that the charge per surface area (or charge density = charge per unit volume) is the highest for $L{i}^{+}$. Hence, in the solvated state, the hydration sphere is the largest for $L{i}^{+}$. Hence, its ionic mobility will also be the lowest.