Info Sheet Chemical Nomenclature Cation: positively charged ion. Anion: negatively charged ion. Binary compound: compound that contains only two different elements. Polyatomic ion: charged molecule (ion that contains more than one atom). Stock system: use of Roman numerals in a chemical name to indicate the charge on the metal ion. Metal and nonmetal = ionic compound Positive ion and negative ion = ionic compound Nonmetal or metalloid and nonmetal or metalloid = covalent compound Metal and metal = alloy (not a compound, not covered here) • Covalent compounds o Use prefixes to indicate the number of atoms of each element in the compound. (mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona-, deca-) o Second element has suffix –ide o Example: dinitrogen pentaoxide is N2O5 o Compounds known by their common names: H2O water, NH3 ammonia, CH4 methane • Ionic compounds o No prefixes. o Name of compound is the name of the positive ion followed by the name of the negative ion. o Charges must balance out to zero. o Use the charges on the ions to figure out the formula. o Use the formula to figure out the charges on the ions. o Never write the charges in the chemical formula of ionic compounds. o Examples: aluminum oxide is Al2O3, ammonium phosphate is (NH4)3PO4 • Names of ions o Metals ! For metals with fixed charges (alkali metals, alkaline earth metals, plus Al, Zn, Ag, Cd): name of ion = name of metal Examples: sodium, magnesium, aluminum. ! For all other metals: name of ion = name of metal with Roman numeral indicating charge on the metal Examples: iron(II), iron(III), vanadium(V) o Nonmetals ! Name of ion = root name of element with –ide suffix Examples: fluoride, iodide, sulfide, telluride. ! Acids containing ions with …–ide ending have names like hydro-…-ic acid. o Polyatomic ions ! -ide suffix is mainly for single-element ions (except hydroxide and cyanide) Examples: oxide, phosphide, arsenide. ! Polyatomic ions prefixes and suffixes: per-…-ate, …-ate, …-ite, hypo-…-ite (learn the patterns!!) Examples: sulfate, sulfite, selenate, selenite. ! Acids containing these ions have names following a similar pattern: …-ate ions have …–ic acid ending, and …–ite ions have …–ous acid ending. ! bi- prefix for some polyatomic ions (learn which ones) Examples: bicarbonate, bisulfite. ! Learn the naming patterns and the names will be easier to remember. ! A few polyatomic ions have names that don’t fit into any patterns. Examples: ammonium, hydroxide, cyanide, acetate. .