Which of the following alkaline earth metal ions exhibits the highest ionic mobility in an aqueous solution?

Step-by-step solution

The ionic mobility of an ion in an aqueous solution is inversely proportional to its hydrated radius. A larger hydrated radius leads to lower mobility due to increased viscous drag. The extent of hydration of an ion depends on its bare ionic size. Smaller ions have a higher charge density, leading to a greater degree of hydration and a larger hydrated radius. The bare ionic radii of the given ions increase down the group: Be ²⁺ Consequently, the hydrated radii follow the reverse order: Be ²⁺_ ( aq ) > Mg ²⁺_ ( aq )