Ionic Bonding

When an ionic compound is formed, the ions must combine in a way that the total charges of the compound equal zero. For example, let's write the correct formula for magnesium chloride. The first step is to write the formulas for the cation Mg²⁺ and anion Cl⁻. Next, drop the positive and negative signs; crisscross the superscripts so that they become subscripts and reduce when possible by finding the least common multiple. In this example, the two chlorine ions, with a total charge of -2, balance the +2 charge of the magnesium ion. The cation is always listed first before the anion, resulting in the formula MgCl₂.