Iron and chlorine will not form an ionic compound. Instead, they form a covalent compound, iron(III) chloride. This is because iron is a metal and chlorine is a nonmetal, and metals and nonmetals typically form covalent compounds. In an ionic compound, one atom loses electrons to another atom, resulting in the formation of positive and negative ions. However, in a covalent compound, the atoms share electrons, so no ions are formed.