The correct order of atomic sizes is

Options

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

Answer

D

Explanation

`Mg^(2+),Na^(+),F^(-)` are isoelectronic ions (having two filled order : `Mg^(2+) lt Na^(+) lt F^(-)`. Al belongs to the 3rd period and also does not carry any charge. Hence it has the largest size. `:.` Over all sizes increases in the order `Mg^(+2) lt Na^(+) lt F^(-) lt Al`.