The species Ar, `K^(+)` and `Ca^(2+)` contain the same number of electrons. In which order do their radii increase-

Options

A. `Ca^(2+) lt K^(+) lt Ar`
B. `K^(+) lt Ar lt Ca^(2+)`
C. `Ar lt K^(+) lt Ca^(2+)`
D. `Ca^(2+) lt Ar lt K^(+)`

Answer

A

Explanation

For isoelectronic species atomic/ionic radiii decreases with the increasae of nuclear charge. Hence increasing order of atomic/ionic radii `""_(20)Ca^(2+) lt ""_(19)K^(+) lt ""_(18)Ar`