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

Explanation

Atomic radius decreases across the period. Here Mg and Al belong to the same period, so out of these two, Mg will have the larger size.
Cation are smaller than their parent atoms due to higher effective nuclear charge. Among the isoelectronic species, the one with a greater positive charge will have smaller radius . Hence, we can say out of `Mg, Mg^(2+), Al " and " Al^(3+)` the largest size will be of Mg and smallest size is of `Al^(3+)`.