Compounds Nomenclature for AP Chemistry
Practice problems for these concepts can be found at:
- Basics Multiple Choice Review Questions for AP Chemistry
- Basics Free-Response Questions for AP Chemistry
This overview covers some of the rules for naming simple inorganic compounds. There are additional rules, and some exceptions to these rules. The first part of this overview discusses the rules for deriving a name from a chemical formula. In many cases, the formula may be determined from the name by reversing this process. The second part examines situations in which additional information is needed to generate a formula from the name of a compound. The transition metals present some additional problems; therefore, there is a section covering transition metal nomenclature and coordination compounds.
Binary compounds are compounds that consist of only two elements. Some binary compounds have special names, and these special names supersede any of the rules given below. H2O is water, NH3 is ammonia, and CH4 is methane. All other binary compounds have a name with a suffix ide. Binary compounds may be subdivided into metal type, nonmetal type, and acid type.
- Metal type These binary compounds begin with metals. The metal is given first in the formula. In general, metals are the elements on the left-hand side of the periodic table, and the nonmetals are on the right-hand side. Hydrogen, a nonmetal, is an exception to this generalization.
- Nonmetal type These binary compounds have formulas that begin with a nonmetal. Prefixes are used to indicate the number of each atom present. No prefixes are used for hydrogen. Naming the compounds can best be explained using the following examples:
- Acid type These binary compounds have formulas that begin with hydrogen. If the compound is not in solution, the naming is similar to that of the metal type. If the compound is dissolved in H2O, indicated by (aq), the compound takes on the prefix hydro and the suffix ic. If the compound is not in solution, the state of matter should be shown as follows:
First name the metal, then name the nonmetal with the suffix ide. Examples:
The ammonium ion is often treated as a metal, and its compounds are named under this rule. Thus, NH4Cl is named ammonium chloride.
Carbon monoxide is one of the very few cases where the prefix mono is used. In general, you should not use mono in any other compound.
Some of the prefixes used to denote the numbers of atoms in a compound are listed below:
On many occasions the terminal a or o is dropped for oxides, so they read as pentoxide, heptoxide, or monoxide.
In normal nomenclature, the nonmetal prefixes are not used if a metal is present. One of the few exceptions to this is MnO2, sometimes called manganese dioxide.
If the formula has no designation of phase or water, either name may be used. Examples for naming these compounds are:
HCN (hydrocyanic acid) is named using these rules. However, in this case, it does not matter if the phase or water is indicated.
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