The one with the largest ionic size is

Options

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

Explanation

`O^(2-), F^(-)Mg^(2+)` and `Na^(+)` are isoelectronic species (each having `10 e^(-)`). The size of isoelectronic species decreases with increase in nuclear charge (number of protons). Hence, correct order of size is
`O^(2-)gt, F^(-)gt Na^(+)gt Mg^(2+)`