Which of the following is the correct order of hyrated ionic radii ?

Options

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

Answer

C

Explanation

For a given charge, 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. Thus, the correct order of hydrated radius is
`Li^(+) lt Na^(+) lt K^(+) lt Rb^(+) lt Cs^(+)`
`Li^(+)` ion is the most hydrated on account of maximum charge density due to the smallest size.