The correct order of the size is

Options

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

Answer

B

Explanation

A cation has always the lesser ionic size than a metal atom due to loss of electrons and an anion has always the greater size than metal atom due to gain of electrons. The given species are isoelectronic species as they contain same number of electrons. For isoelectronic species ionic radi.
`prop (1)/("atomic number")`
`{:(,"Ion",:,Ca^(2+),K^(+),Ar,S^(2),CL),(,"Atomic number",:, 20,19,18,16,17):}`
So, the correct order of size is as
`Ca^(2+) lt K^(+) lt Ar lt Cl^(-) lt S^(2-)`