Chemistry - Complete s-block Question with Solution | TestHub

The mobility of alkali metal ions in aqueous solution is inversely proportional to their hydrated size. Smaller ions have a higher charge density, leading to stronger hydration and larger hydrated radii. Thus, Cs⁺ has the smallest hydrated radius and highest mobility, while Li⁺ has the largest hydrated radius and lowest mobility.

Therefore, the correct order of mobility is:

Cs⁺ > Rb⁺ > K⁺ > Na⁺ > Li⁺