The correct order of radii is:

Options

A. `N lt Be lt B`
B. `F^(-) lt O^(2-) lt N^(3-)`
C. `Na lt Li lt K`
D. `Fe^(3+) lt fe^(2+) lt Fe^(+4)`

Answer

B

Explanation

All are isoelectronic species having 10 electrons in each species but different nuclear charge and thus ionic
radius `prop (1)/("Nuclear charge")`.
So correct order is `_(9)F^(-) lt ._(8)O^(2-) lt ._(7)N^(3-)`.