Which one of the following ions has the highest value of ionic radius?

Options

A. `Li^(+)`
B. `F^(-)`
C. `O^(2-)`
D. `B^(3+)`

Answer

C

Explanation

`Li^(+) (Z=3) : 1s^(2)`
`F^(-)(Z=9) : 1s^(2)2s^(2)2p^(6)`
`O^(2-) (Z=8) :1s^(2)2s^(2)2p^(6)`
the correct order of ionic radii is
`B^(3+) lt Li^(+) lt F^(-) lt O^(2-)`
for isoelectronic species, more the nuclear charge, smaller the size. further `Li^(+)` and `B^(3+)` have only one shell and as such smaller than `F^(-)` and `O^(2-)` when have two shells .