|Understanding the concepts
||A binary compound is composed of two elements.
||An ionic compound results where the metal forms a cation and the nonmetal forms an anion. The metal cation is always named first.|
||Some metal ions form more than one type of ion in compounds. Therefore, the charge on the metal ion must be indicated in the name so one knows which charged metal ion is present. If the charge is not indicated in the name, then you don't know which compound is present. For example, iron oxide could be FeO or Fe2O3 since iron forms +2 and +3 charged ions. However, iron(III) oxide must be Fe2O3.|
||Formulas for nonmetal binary compounds are extremely difficult to predict and some elements form a variety of different binary compounds. Since you can't predict formulas, the numbers of atoms present must be indicated in the name.|
||Polyatomic ions are charged species (anions or cations), which are composed of several atoms bound together.|