# The sequence of ionic mobility in aqueous solution is :

$\begin {array} {1 1} (1)\;Na^+>K^+>Rb^+>Cs^+ & \quad (2)\;K^+>Na^+>Rb^+>Cs^+ \\ (3)\;Cs^+>Rb^+>K^+>Na^+ & \quad (4)\;Rb^+>K^+>Cs^+>Na^+ \end {array}$