* Ionic Compounds: Zinc (Zn) is a metal and iodine (I) is a nonmetal. This indicates an ionic compound where the metal loses electrons to become a cation (Zn²⁺) and the nonmetal gains electrons to become an anion (I⁻).
* Charge Balance: The charges of the ions must balance to form a neutral compound. The most common ionic form of zinc is Zn²⁺, and iodine typically forms the anion I⁻.
* Finding the Correct Formula: To find the correct formula, you need to determine the smallest whole-number ratio of ions that results in a neutral compound. Since Zn²⁺ has a +2 charge and I⁻ has a -1 charge, we need 2 iodine ions (2 x -1 = -2) to balance the +2 charge of zinc. Therefore, the correct formula for zinc iodide is ZnI₂.
Key takeaway: Chemical formulas must represent the correct ratio of atoms or ions to ensure charge neutrality in the compound.
