The formula for potassium iodide, KI, does illustrate the octet rule. Potassium has one valence electron, and iodine has seven valence electrons. When potassium and iodine form an ionic compound, potassium donates its valence electron to iodine, resulting in the formation of K+ and I- ions. The K+ ion has a full octet of electrons, and the I- ion has a full octet of electrons. Therefore, the formula for potassium iodide, KI, illustrates the octet rule.