The correct order of the size is

Options

A. `Ca^(2+) lt Ar lt K^(+)C1^(-) lt S^(2-)`
B. `Ca^(2+) lt K^(+) lt AR lt S^(2-) lt C1^(-)`
C. `Ca^(2+) + K^(+) lt Ar lt C1^(-) lt S^(2-)`
D. `Ar lt Ca^(2+) lt K^(+) lt c1^(-) lt S^(2-)`

Answer

C

Explanation

They are all isolectronic species with the following configuration: `1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)`. For such species, size decreases with the increase of nuclear charge (atomic number):
`Ca^(2+) (20) lt K^(+) (19) lt Ar (18) lt C1^(-)(17) lt S^(2-) (16)`