Which one of the following is the largest ion?

Options

A. `Na^(+)`
B. `Mg^(2+)`
C. `O^(2-)`
D. `F^(-)`

Answer

C

Explanation

Nuclear charge `prop(1)/("lonic size")`
`O^(2) = 10e^(-) = 8p` nuclear charge
`F^(-) = 10e^(-) = 9p` nuclear charge
`Na^(+) = 10e^(-) = 11p` nuclear charge `Mg^(2+)= 10e^(-) = 12p` nuclear charge
So, `O^(2-)` has least nuclear charge and largest size among the given ions.