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

They are isoelectronic species but their nuclear charges are Ca = 20, K = 19, Ar = 18. Greater the nuclear charge of the isoelectronic species, greater is the pull on the electrons and smaller is the size