The ions `O^(2-), F^(-), Na^(+), Mg^(2+)`, and `A1^(3+)` are isolectronic. Their ionic radii show

Options

A. an increase from `O^(2-)` to `F^(-)` and then decrease form `Na^(+)` to `Al^(3+)`
B. a decrease form `O^(2-)` to `F^(-)` and then increase form `Na^(+)` to `Al^(3+)`
C. a significant increases form `O^(2-)` to `Al^(3+)`
D. a significant decrease form `O^(2-)` to `Al^(3+)`

Answer

D

Explanation

On increasing atomic number of isoelectronic , species ionic radii decreases due to increasing effective nuclear charge `(Z_("eff"))`
`"Radius"prop(1)/("Atomic number")prop (1)/(Z_("eff"))`
So, as the negative charge increases ionic radii increases while on increasing positive charge ionic radu decreases. Anions having higher ionic radil than the cation
`O^(2+) gt F^(-) gt Na^(+) gt Mg^(2+) gt Al^(3+)`