Principles of Chemical Nomenclature

James Richard Fromm

Chemical nomenclature simply means the naming of chemical compounds. The names we give to chemical compounds reflect our understanding of their structure and their nature.

Prior to about 1800, when the first systematic approach to giving names to chemical compounds was developed by Antoine L. Lavoisier and his colleagues in France, every known compound had its own specific name. Some were named for their color, such as martial ethiops, which is the black oxide of iron, Fe3O4. Others had Arabic names, such as alcohol, C2H5OH; some had Latin names, such as sal ammoniac, NH4Cl. Some were named after the men who discovered them (Glauber's salt, Na2SO4), and some were named after their physical properties (butter of antimony, SbCl3, from its consistency).

Principles of Chemical Nomenclature

Modern chemical nomenclature is derived from Lavoisier's systematic approach and follows his major principles, which are:

  1. To each and every compound there can correspond one and only one correct name; to each and every name there can correspond one and only one compound.
  2. The proper name of a compound is the simplest systematic name which can unambiguously specify the compound being spoken of.
  3. Chemical elements, which are the simplest forms into which materials can be resolved by chemical means, react with each other to yield chemical compounds containing various proportions of two or more elements. Therefore the names of compounds should be derived from the names of the elements of which they are composed.

These three principles were originally fundamental to all chemical nomenclature. Later, as chemistry evolved into the two traditional areas of organic and inorganic chemistry, the third principle was retained only for inorganic compounds, for the following reasons. Organic chemistry is the study of the covalent compounds based on the elements carbon and hydrogen. Because organic chemistry is the study of carbon-hydrogen compounds, organic compounds are named by giving the chain or other structure of the carbon-hydrogen atoms and substituting into that structure the names of any other elements or groups of elements and the particular places at which they are present.

Inorganic compounds, however, are still named according to the principle that the name of an inorganic compound is derived from the names of the chemical elements which make up that compound. There are many more different types of inorganic compounds, even though the number of known organic compounds is very much greater than the number of known inorganic compounds.

It would be false to give you the impression that there is one and only one rigid system of naming either organic or inorganic compounds. Since names are derived from an understanding of the nature and the structure of the compounds, nomenclature systems used must allow for improvements in understanding and also in names. On the other hand, nomenclature systems cannot permit excessive changes in names. Imagine the confusion if oak trees were called zork trees from January 1, 1960 to January 1, 1970 and goflump trees thereafter, for example; it would take a generation or more to sort out the mess. The chemical nomenclature described here is the current nomenclature. It reflects that of the past; we may expect slight alterations in the future.

Copyright 1997 James R. Fromm