Which of the following species will have the largest size?

Options

A. `A1^(3+)`
B. `A1`
C. `Mg^(2+)`
D. `Mg`

Answer

D

Explanation

Atomic radii decrease across a period `(Mg rarr A1)`. Cations are always smaller than their parent atoms. Among isoelectronic species, the one with the larger positive nuclear charge will have a smaller radius: `Mg gt A1 gt Mg^(2+) gt A1^(3+)`