The correct order of ionic mobility of alkali metal ions in aqueous solution is: — s Block Elements Chemistry Question

💡 Solution & Explanation

Hydration energy is inversely proportional to ionic size. $Li^+$ is the smallest ion and gets most extensively hydrated. This makes its hydrated ionic radius the largest, which drags down its mobility. Thus, ionic mobility increases down the group: $Cs^+ > Rb^+ > K^+ > Na^+ > Li^+$.