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Chemical Names

Systematic and Common Names


These are crystals of sodium chloride or table salt.

These are crystals of sodium chloride (systemic name) or table salt (common name).

Mark Schellhase
There are many ways to name a chemical. Here is a look at the difference between different types of chemical names, including systematic names, common names, vernacular names and CAS numbers.

Systematic or IUPAC Name

The systematic name, also called the IUPAC name is the preferred way to name a chemical because each systematic name identifies exactly one chemical. The systematic name is determined by guidelines set forth by the International Union of Pure and Applied Chemistry (IUPAC).

Common Name

A common name is defined by the IUPAC as a name that unambiguously defines a chemical, yet does not follow the current systematic naming convention. An example of a common name is acetone, which has the systematic name 2-propanone.

Vernacular Name

A vernacular name is a name used in a lad, trade or industry that does not unambiguously describe a single chemical. For example, copper sulfate is a vernacular name which may refer to copper(I) sulfate or copper(II) sulfate.

Archaic Name

An archaic name is an older name for a chemical that predates the modern naming conventions. It's helpful to know archaic names of chemicals because older texts may refer to chemicals by these names. Some chemicals are sold under archaic names or may be found in storage labeled with the older names. An example of this is muriatic acid, which is the archaic name for hydrochloric acid and is one of the names under which hydrochloric acid is sold.

CAS Number

A CAS number is an unambiguous identifier assigned to a chemical by the Chemical Abstracts Service (CAS), a part of the American Chemical Society. CAS numbers are assigned sequentially, so you can't tell anything about the chemical by its number. Each CAS number consists of three strings of numbers that are separated by hyphens. The first number contains up to six digits, the second number is two digits, and the third number is a single digit.

Other Chemical Identifiers

Although the chemical names and CAS Number are the most common way to describe a chemical, there are other chemical identifiers you may encounter. Examples include numbers assigned by PubChem, ChemSpider, UNII, EC number, KEGG, ChEBI, ChEMBL, RTES number and the ATC code.

Example of Chemical Names

Putting it all together, here are the names for CuSO4·5H2O:

Systematic (IUPAC) Name: copper(II) sulfate pentahydrate

Common Names: copper(II) sulfate, copper(II) sulphate, cupric sulfate, cupric sulphate

Vernacular Name: copper sulfate, copper sulphate

Archaic Name: blue vitriol, bluestone, copper vitriol

CAS Number: 7758-99-8

Learn More

Covalent Compound Nomenclature
Ionic Compound Nomenclature
Hydrocarbon Nomenclature Prefixes
Alkane Nomenclature and Numbering
Compound Names Quiz

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