Question

The correct order of the mobility of the alkali metal ions in aqueous solution is

• A. $Li^+ > Na^+ > K^+ > Rb^+$
• B. $Na^+ > K^+ > Rb^+ > Li^+$
• C. $K^+ > Rb^+ > Na^+ > Li^+$
• D. $Rb^+ > K^+ > Na^+ > Li^+$

Answer 1

Answer: (D)

$Rb^+ > K^+ > Na^+ > Li^+$

Answer 2

Charge density $\propto$ hydration. Therefore hydrated
size of $Li ^{+}$ is large and having less mobility. Down the group degree of hydration decreases.