Which of the following species will have the largest and smallest size? `Mg,Mg^(2+),Al,Al^(3+)`

Explanation

Mg and Al belongs to third period and we know that along a period, atomic radii decreases. Hence `Al ltMg`. In case isoelectronic species, size decreases as nuclear charge increases. Hence `Mg^(2+)gtAl^(3+)` Also size of cation is always smaller than its parent atom.
`:.` Correct order size is `Al^(3+)ltAlltMg^(2+)ltMg` So, Mg is largest and `Al^(3+)` is smallest in the given species.