Section 3: Naming Ionic Compounds

Learning Goals Distinguish between common and systematic names for compounds. Name binary ionic compounds containing a metal that forms only one type of ion. Name binary ionic compounds containing a metal that forms more than one type of ion. Name ionic compounds containing a polyatomic ion.

Naming Compounds Chemists have developed systematic ways to name compounds. If you learn the naming rules, you can examine a compound’s formula and determine its name, and vice versa. Many compounds also have a common name. NaCl has the common name salt and the systematic name sodium chloride.

Naming Ionic Compounds Identify if the metal cation has more than one potential charge. Such metals are usually (but not always) found in the transition metals section of the periodic table. Notable Exceptions: Always Zn2+ and Ag+ Sn and Pb can have multiple charges

Binary Ionic Compounds Binary compounds are those that contain only two different elements. The names for binary ionic compounds containing a metal that forms only one type of ion have the following form: Name of Cation + Base Name of Anion + ide

Binary Ionic Compounds Since the charge of the metal is always the same for these types of compounds, it need not be specified in the compound’s name. Example: MgF2

Binary Ionic Compounds

Practice Name these compounds: CaO Al2O3 KF MgCl2 Li3N

Practice Write the formula for these ionic compounds: Potassium bromide Sodium oxide Zinc nitride

Binary Ionic Compounds If the cation could have more than one charge, then the charge must be specified in the metal’s name. We specify the charge with a Roman numeral (in parentheses) following the name of the metal.

Binary Ionic Compounds For example, we distinguish between Cu+ and Cu2+ by writing a (I) to indicate the 1+ ion or a (II) to indicate the 2+ ion: Cu+ Copper(I) Cu2+ Copper(II)

Binary Ionic Compounds These compounds are named using the following form: Name of Cation (charge of metal in roman numerals) Base Name of Anion + ide + +

Binary Ionic Compounds We can determine the charge of the metal from the chemical formula of the compound. The sum of all the charges must be zero.

Binary Ionic Compounds What is the charge of iron in FeCl3? +3 What is the name for FeCl3? Iron (III) Chloride

Practice Name the following compounds: PbCl4 PbO Explain why CaO is not named calcium (II) oxide.

Practice Write the formula for the following compounds: Chromium (II) chloride Tin (IV) oxide Iron (III) oxide

Polyatomic Ionic Compounds Ionic compounds containing polyatomic ions are named using the same procedure we apply to other ionic compounds, except that we use the name of the polyatomic ion whenever it occurs.

Polyatomic Ionic Compounds For example, we name KNO3 using its cation, K+, potassium, and its polyatomic anion, NO3-, nitrate. KNO3 potassium nitrate

Practice Fe(OH)2 NH4NO3

Practice Write the formula for the following compounds: barium nitrate ammonium iodide iron (III) hydroxide

Polyatomic Ionic Compounds Many polyatomic ions are oxyanions, anions containing oxygen. When a series of oxyanions contain different numbers of oxygen atoms, they are named systematically according to the number of oxygen atoms in the ion.

Polyatomic Ionic Compounds If there are two ions in the series, the one with more oxygen atoms is given the ending -ate and the one with fewer is given the ending -ite. NO3− nitrate SO42− sulfate NO2− nitrite SO32− sulfite

Polyatomic Ionic Compounds If there are more than two ions in the series, then the prefixes hypo-, meaning “less than,” and per-, meaning “more than,” are used. ClO − hypochlorite BrO − hypobromite ClO2− chlorite BrO2− bromite ClO3− chlorate BrO3− bromate ClO4− perchlorate BrO4−perbromate

Practice K2CrO4 Mn(NO3)2

Practice Write the formula for the following compounds: sodium perchlorate sodium chlorite sodium nitrate sodium nitrite