The ions which are arranged in correct order of increasing radii are

Options

A. `K^(+), Ca^(2+), S^(2-)`
B. `Be^(2+),Mg^(2+),Na^(+)`
C. `O^(2-),F^(-),N^(3-)`
D. `S^(2-),O^(2-),As^(3-)`

Answer

B

Explanation

size increases down the group and decreases along a period. `Be^(+2)` belong to 2nd period wheras Na and Mg are of 3rd period.