JEE Main 17 March 2021 Shift 1 Solved Paper

Correct order of conductivity of ions in water is
Cs+>Rb+>K+>Na+
Cs+(aq) has lower hydrated radius so its electrical conductivity is higher.
Extent of hydration depends on charge density on the ion.
As the size of gaseous ion decreases, it get more hydrated in water and hence, the size of aqueous ion increases. When this bulky ion move in solution, it experience greater resistance and hence lower conductivity.
Size of gaseous ion: Cs+>Rb+>K+>Na+
Size of aqueous ion: Cs+<Rb+<K+<Na+
Conductivity: Cs+>Rb+>K+>Na+