The correct arrangement for the ions in the increasing order of their radii is

Options

A. `Na^(+), Cl^(-), Ca^(2+)`
B. `Ca^(2+), K^(+), S^(2-)`
C. `Na^(+), Al^(3+), Be^(2+)`
D. `Cl^(-), F^(-), S^(2-)`

Answer

B

Explanation

The species `Ca^(2+), K^(+)` and `S^(2-)` are isoelectronic.
For isoelectronic ions, the radius decreases as the nuclear charge increases.
Hence, the increasing order of their radii is
`Ca^(2+) lt K^(+) S^(2-)`