Wikipedia:Naming conventions (chemistry)

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This page documents an English Wikipedia naming convention. It is a generally accepted standard that editors should attempt to follow, though it is best treated with common sense and the occasional exception. Any substantive edit to this page should reflect consensus. When in doubt, discuss first on the talk page.

Shortcuts: WP:CHEMNAME WP:NCCHEM

Main article: Wikipedia:Naming conventions

1 General rule
2 IUPAC preferred name vs. systematic name
3 Element names
4 Use of Stock nomenclature
5 Drug-related articles
6 Prefixes
7 Redirects
8 Exceptions
9 Capitalization of elements and compounds
10 See also
11 References
12 Resources

General rule

From Wikipedia:Naming conventions:

"Generally, article naming should give priority to what the majority of English speakers would most easily recognize, with a reasonable minimum of ambiguity, while at the same time making linking to those articles easy and second nature."

IUPAC preferred name vs. systematic name

IUPAC recommends ^[1] the use of non-systematic names for some organic compounds, and these recommendations should be followed in article titles. Examples:

Acetic acid	not	Ethanoic acid
Toluene	not	Methylbenzene
Lysine	not	2,6-Diaminohexanoic acid

Element names

Traditionally, the names of three elements have been spelled differently in US and British English. For articles about chemical substances, Wikipedia follows the recommendations of the International Union of Pure and Applied Chemistry (IUPAC) as follows:^[2] ^[3]

Aluminium	not	Aluminum
Sulfur	not	Sulphur
Caesium	not	Cesium

These international standard spellings should be used in all chemistry-related articles on English Wikipedia, even if they conflict with the other national spelling varieties used in the article.

This convention should also be applied to all compounds and derivative names of these chemicals: e.g. sulfate not sulphate; sulfuric not sulphuric; etc.

Use of Stock nomenclature

Stock nomenclature for inorganic compounds is based on the indication of the oxidation number (as a roman numeral, in parentheses) of each of the major elements in the compound, e.g. iron(III) chloride. It is widely, if sometimes incorrectly, used on Wikipedia for the titles of articles about inorganic compounds. It is not obligatory, as there are other acceptable methods for naming these compounds, but it is often preferred as the most common non-ambiguous name for a substance. The following guidelines are based on current WikiBestPractice:

Only the cationic element (i.e. the element whose name appears unchanged in the compound name) is assigned its oxidation number. Except in rare cases (none at present), we do not assign the oxidation number in the anion: hence potassium permanganate not potassium manganate(VII), sodium hypochlorite not sodium chlorate(I).
There is no space between the end of the element name and the opening parenthesis: hence silver(I) fluoride not silver (I) fluoride. Note that this is an exception to the usual English style for parentheses.
It is not necessary to specify the oxidation number when there is no possibility of ambiguity in the compound title: hence sodium chloride not sodium(I) chloride.
Stock nomenclature should only be used for ionic compounds. Compounds with a substantial degree of covalency should be named by stoichiometric nomenclature: hence titanium tetrachloride not titanium(IV) chloride.
Stock nomenclature should not be used for compounds with mixed or non-integral oxidation numbers: hence triiron tetraoxide not iron(II,III) oxide (in fact, this article is difficult to name and, as an exception, redirects to magnetite).

Drug-related articles

Prefixes

For technical reasons, it is not recommended to use non-numerical prefixes in article titles. This includes:

Positional identifiers	ortho-, meta-, para-, α-, β-, γ-
Stereochemical identifiers	cis-, trans-, (E)-, (Z)-
Chiral identifiers	(R)-, (S)-, D-, L-, (+)-, (−)-

Note that iso in such compounds as isopropanol is not only permitted but recommended. No hyphen is used in these cases. sec- and tert- are hyphenated and non-capitalized, and should be avoided if possible on Wikipedia.

When the chosen article title starts with a number, the first letter of the compound name should be capitalized: hence 1,1,1-Trichloroethane not 1,1,1-trichloroethane. A redirect from the uncapitalized version should be created to simplify linking from other articles. See also Capitalization below.

Redirects

From Wikipedia:Deletion policy: "Don't worry, redirects are cheap."

Redirects should be created for:

Alternative names for the compound, including acronyms where appropriate;
Alternative capitalizations, where there is a numerical prefix in the article title;
Formulas of simple compounds; for example H2O -> water.

Exceptions

Even with the best will in the world, no set of guidelines can cover every case. Some articles on Wikipedia have non-standard titles through consensus that this is the most commonly used name (in scientific circumstances) for the compound concerned, whatever IUPAC or the other rules suggest. For example:

Ethylene oxide not oxirane

Phosphine not phosphane (and for substituted phosphines, arsine and stibine)

Wilkinson's catalyst not chlorotris(triphenylphosphane)rhodium

Vaska's complex not carbonylchlorobis(triphenylphosphane)iridium

Please do not get into revert wars over the naming of an article: the best place for discussion is on the article's talk page or (failing that) at Wikipedia talk:WikiProject Chemicals.

Capitalization of elements and compounds

The names of chemical compounds and chemical elements when written out, are common nouns in English. They are capitalized at the beginning of a sentence or title, but not elsewhere. Note that for chemical elements this applies to the word only and not the chemical symbol, which is always capitalized. Both rules remain even with chemical elements derived from proper names which would otherwise be capitalized, in keeping with IUPAC policy to differentiate proper names from things named after proper names. Thus, it is californium but the symbol is Cf, and einsteinium, but symbol Es. Note that names for odd or rare chemicals are uncapitalized like common ones, and thus uranium and plutonium (symbols U and Pu) should be uncapitalized like carbon or iron (symbols C and Fe). This rule (full name uncapitalized but symbol capitalized) applies also to isotopes and nuclides, when completely written out: thus ¹⁴C but carbon-14. IUPAC Provisional Recommendations for the Nomenclature of Inorganic Chemistry (2004). (The element mercury is uncapitalized, but of course the planet and god Mercury remain capitalized proper nouns).

Prefixes such as sec-, tert, ortho-, meta-, para- and the numerical prefixes are not considered part of the name: the first letter of main part of the name should still be capitalized where appropriate. The exception is iso-, which is part of the name and therefore not italicized or hyphenated. Substituent groups do form part of the name: hence the correct article title is 2-Aminoethanol, which is written as 2-aminoethanol if not at the start of a sentence. Note that the two wikilinks refer to separate articles: one is a redirect to the other.

References

^ Panico, R.; & Powell, W. H. (Eds.) (1994). A Guide to IUPAC Nomenclature of Organic Compounds 1993. Oxford: Blackwell Science. ISBN 0-6320-3488-2.