* Aluminum (Al) is a metal in group 3, meaning it tends to lose 3 electrons to form a +3 cation (Al³⁺).
* Iodine (I) is a nonmetal in group 17, meaning it tends to gain 1 electron to form a -1 anion (I⁻).
To form a neutral compound, the charges must balance. Therefore, we need three iodide ions (3 x -1 = -3) to balance the +3 charge of the aluminum ion.
