The alkali metal cation having the least ionic mobility is

Options

A. `Li^(+)`
B. `Na^(+)`
C. `K^(+)`
D. `Cs^(+)`

Answer

A

Explanation

The extent of hydration depends upon the size of the ion. Smaller the size of the ion, more highly it is hydrated and, hence, greater is its hydrated ionic radius, and less is its ionic mobility (condcutance). Thus, the order of ionic mobility is
`Li^(+)ltNa^(+)ltK^(+)ltRb^(+)ltCs^(+)`