The set representing the correct order of ionic radius is

Options

A. `Li^(+) gt Be^(2+) gt Na^(+) gt Mg^(2+)`
B. `Na^(+) gt Li^(+) gt Mg^(2+) gt Be^(2+)`
C. `Li^(+) gt Na^(+) gt Mg^(2+) gt Be^(2+)`
D. `Mg^(2+) gt Be^(2+) gt Li^(+) gt Na^(+)`

Answer

B

Explanation

Down the group ionic radii increases with increasing atomic number because of the increase in the number of atomic shells but across the period the ionic radii decreases due to increase in effective nuclear charge as electrons are added in the same shell. `Li^(+) and Mg^(2+)` are diagonally related, so correct order is `Na^(+) gt Li^(+) gt Mg^(2+) gt Be^(2+)`
`Be^(2+)= 0.31 Å`
`Mg^(2+) = 0.72 Å`
`Li^(+) = 0.76 Å`
`Na^(+) = 1.02 Å`