Wikipedia:WikiProject Chemicals/Style guidelines

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These style guidelines have been replaced by the Chemistry Manual of Style. Please make changes at Wikipedia:Manual of Style (chemistry)

These guidelines have been put together by the WikiProject Chemicals to help editors improve the 4000 or so articles on Wikipedia which are about chemical compounds.


There is a misconception among certain editors that the title of a chemical compound article must be the systematic name of the compound. Most commonly the systematic name is not preferred, although it (and other common names) should be redirects.

General rule[edit]

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[edit]

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[edit]

Traditionally, the names of three elements have been spelt differently in US and British English. With the onset of computer searching of databases, it was felt necessary to standardize these spellings as follows:[2]

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. These "preferred names" conform with IUPAC nomenclature.

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[edit]

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:

  1. 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).
  2. 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.
  3. The oxidation number is not specified when the name is otherwise unambiguous: hence sodium chloride not sodium(I) chloride.
  4. 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.
  5. 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[edit]

See also WikiProject Drugs
Where a compound has a WHO International Nonproprietary Name (INN), this should be used as the article title.


For technical reasons, the use of non-numerical prefixes in article titles is discouraged. Common chemical prefixes include:

Positional identifiers 1-, 2-, 3-, ortho-, meta-, para-, α-, β-, γ-, [a,b]- 1-, 2-, 3-, ''ortho''-, ''meta''-, ''para''-, α-, β-, γ-, [''a,b'']-
Stereochemical identifiers cis-, trans-, (E)-, (Z)- ''cis''-, ''trans''-, (''E'')-, (''Z'')-
Chiral identifiers (R)-, (S)-, D-, L-, (+)-, (−)-, d-, l- (''R'')-, (''S'')-, <small>D</small>-, <small>L</small>-, (+)-, (−)-, ''d''-, ''l''-
Element identifiers H-, N-, O-, S- ''H''-, ''N''-, ''O''-, ''S''-
Isomer identifiers n-, iso-, sec-, tert- ''n''-, ''iso''-, ''sec''-, ''tert''-
"iso" in compounds such as isopropanol is part of the name and not a prefix – no hyphen is used in these cases.
Many prefixes are italicized, see the right column of the table above for the correct wikitext formatting.
The capitalization of prefixes never changes - instead, the standard capitalization rules are applied to the first letter of the main name, ignoring any prefixes and numbers. Correct article names and first words in sentences are:
A redirect from the uncapitalized version should be created to simplify linking from other articles. See also Capitalization below.

Long names[edit]

Names of chemical compounds can be long. This may effect suboptimal layout in older browser software. However, proper chemical names should be adhered to.


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.


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.

Article format[edit]


Wikipedia:WikiProject Chemicals strongly recommends the use of chemical infoboxes for the following reasons:

  • If basic (often numerical) data is included in the article text, the readability of the article is reduced.
  • They reflect a certain consensus as to what data is appropriate for an encyclopedic article.
  • They promote a common visual style among Wikipedia articles on a given subject area.
  • They are well supported by the MediaWiki software (unlike HTML tables), and easily adapted (by individual editors) to the different needs of different articles.

The chembox to use is {{Chembox}}. It is a modular, expandable infobox. Just use the parameters which you need; empty values will not be displayed.

To include a chembox in an article:

  1. Open {{Chembox}} and copy the relevant (simple, medium, full) box desired, and paste into a text editor
  2. Open the relevant reference (e.g. MSDS, Merck Index, CRC Handbook, etc.) and input the data into the template
  3. Copy the filled-out template into the relevant Wikipedia article.

For formatting reasons, the code for the infobox should be at the very beginning of the source code.

Introductory paragraph[edit]

See also: Wikipedia:Lead section

Introductory paragraph should classify the compound either generally (organic compound vs inorganic compound) or more specifically (e.g., organometallic compound or organoarsenic compound). A few properties should be described, assuming STP and noteworthy features mentioned (e.g. extreme toxicity, odor, hygroscopicity). For simpler organic compounds, the main functional group is mentioned, whereas for complex molecules, a parent molecule should be mentioned. Alternative names and routine properties (m.p., density) are ordinarily placed in the Chembox, not in the lede.


This section is often not needed. A discussion of properties is more important for chemicals encountered in everyday life and for solids, where “collective" properties (magnetism, hardness, conductivity) are important. The properties of small organic molecules can be surmised from data in the Chembox and generally do not require extended discussion. Often this section is combined with a description of structure, which summarizes the molecular structure and/or crystal packing (for extended solids). Bond distances are quoted in picometers or angstroms.


If the compound occurs naturally, it can be mentioned here. If natural sources are industrially significant, some discussion should be included. Avoid one-sentence sections — such data can be left in the lead.


All articles about chemical compounds should include one or more methods of preparation in this order:

  • industrial production. Production figures give readers a sense of the commercial significance of a compound.
  • biosynthesis
  • laboratory-scale preparation

Different methods of synthesis/production may merit full-fledged subheadings. Even articles about compounds that are normally extracted from minerals (e.g. molybdenum disulfide) should ideally have a laboratory route to the same compound. Mention should be made if a compound is routinely available commercially.

Where appropriate, the first synthesis/first characterization of each compound should be mentioned and referenced to the original article. Apart from that, "foolproof" syntheses such as those listed in Organic Syntheses and Inorganic Syntheses are preferred. Patented syntheses should be phrased carefully — e.g. "xxx may be synthesized from ... " Being patented does not mean that this synthesis is the best, or that it is used industrially.

When writing about preparations, remember that Wikipedia is not a manual or textbook. In general, preparations should be described in general terms, not as step-by-step instructions giving specific amounts, times, conditions, equipment, and details such as methods of stirring and separation.

Uses and/or reactions[edit]

The order of presentation and allocation of content should reflect the scale of the individual applications. Large-scale applications should be listed first. Lay editors will naturally tend to enumerate domestic uses. Wikipedia does not aspire to report all niche uses. Avoid lists: try to group the various uses by similarity into a coherent paragraph.

If reactions are to be described, emphasize the well established reactions (e.g. those in Organic and Inorganic Syntheses). Highly specialized reactions that are neither broadly applicable nor illustrative are inappropriate.


This paragraph, which is optional, should include the discovery/first synthesis of this compound. Past industrial processes can be described as well. If the etymology of the compound is complicated, it can be included here as well, instead of in the lede.


The majority of compounds are described by a long list of potential hazards as well as R&S phrases. Even innocuous chemicals such as sodium chloride have risk and safety phrases: R36, S26, S36 in their MSDSs. Wikipedia does not aspire to be an MSDS. The hazards associated with a chemical compound should ordinarily be described in the Chembox (via EUClass, NFPA, or MainHazard parameters; further elaborated in R and S phrases). The information in the Chembox is sufficient for most compounds. News reports of routine accidents, even though they may be tragic, are usually not relevant.

Three main rules:

  • If the hazards are relatively obvious (e.g. hexafluorophosphoric acid is a strong acid, and should not be stored with bases and reactive metals) do not create a separate sub-section here.
  • The description of hazards should avoid speculation. This is partly an extension of Wikipedia NPOV policy, but not entirely. There is no need to include a section which merely states "all chemical compounds should be treated with the utmost precaution": such a section tells the reader nothing. If there are no known (or reasonably suspected) hazards, there is nothing for Wikipedia to say.
  • The description of hazards should avoid hyperbole. The role of Wikipedia is to give balanced and accurate information, to allow its readers to reach their own conclusions.

Descriptions of hazards should, as far as possible, be based on published, peer-reviewed sources (which should, of course, be cited at the appropriate point in the article). A list of resources for chemical safety information is given in the external links section of these guidelines.


Depends on the extent of the information, this content may be incorporated into the Safety section or it may be a separate. If the compound is a drug, follow Wikipedia:WikiProject Drugs' recommendations.


Wikipedia is not a buyer's guide. Do not include suppliers' information as they are spam magnets. Such lists are unmaintainable and cause problems. If, however, a particular compound is produced by only one or two suppliers, the suppliers names might be relevant.

See also[edit]

Add concepts in this case. Do not use "See also" to list similar chemical compounds. Use the {{Chembox Related}} module in {{Chembox}} for this purpose.


See: Wikipedia:Footnotes, Wikipedia:Cite your sources

References should emphasize comprehensive sources, see WP:PRIMARY. For books, ISBN’s are helpful. For journal articles, full titles and DOI’s are desirable. There is consensus that the <ref> style of inline citations is to be used throughout articles concerning chemicals. It is preferable to use {{cite journal}}, {{cite encyclopedia}}, and {{cite web}}, though this is not mandatory. For papers published in Organic Syntheses, there is a special citation template ({{OrgSynth}}), which is simpler to fill in.

References should come in a numbered list immediately before the External links section. If footnotes are also used, these should be interspersed with the references and the heading changed accordingly. Notes and references should be numbered sequentially throughout the article by superscript Arabic numerals.

There is no consensus in Wikipedia as a whole for the format of the references, although APA style is suggested as a guideline: this is almost identical to the style used in ACS journals such as J. Am. Chem. Soc. Wikipedia offers a number of citation templates which reproduce this style.

Some commonly used textbook have their own citation templates:

Template Reference
{{BLB}} Brown, Theodore E.; Lemay, H. Eugene; Bursten, Bruce E.; Murphy, Catherine; Woodward, Patrick (2008). Chemistry: The Central Science (11 ed.). New York: Prentice-Hall. ISBN 0136006175.
{{Cotton&Wilkinson4th}} Cotton, F. Albert; Wilkinson, Geoffrey (1980), Advanced Inorganic Chemistry (4th ed.), New York: Wiley, ISBN 0-471-02775-8
{{Cotton&Wilkinson6th}} Cotton, F. Albert; Wilkinson, Geoffrey; Murillo, Carlos A.; Bochmann, Manfred (1999), Advanced Inorganic Chemistry (6th ed.), New York: Wiley-Interscience, ISBN 0-471-19957-5
{{Greenwood&Earnshaw}} Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
{{Loudon}} Loudon, G. Marc (2005), Organic Chemistry (4th ed.), New York: Oxford University Press, ISBN 0-19-511999-1
{{March4th}} March, Jerry (1992), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (4th ed.), New York: Wiley, ISBN 0-471-60180-2
{{McMurray}} McMurry, John E. (1992), Organic Chemistry (3rd ed.), Belmont: Wadsworth, ISBN 0-534-16218-5
{{Merck12th}} Budavari, Susan, ed. (1996), The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals (12th ed.), Merck, ISBN 0911910123
{{RubberBible53rd}} Weast, R. C., ed. (1972). Handbook of Chemistry and Physics (53rd ed.). Cleveland, OH: Chemical Rubber Co.
{{RubberBible83rd}} Lide, D. R., ed. (2002). CRC Handbook of Chemistry and Physics (83rd ed.). Boca Raton, FL: CRC Press. ISBN 0-8493-0483-0.
{{RubberBible86th}} Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
{{Stryer}} Stryer, L.; Berg, J. M.; Tymoczko, J. L. (2002), Biochemistry (5th ed.), New York: W. H. Freeman, ISBN 0716746840
{{VogelOrganic}} Furniss, B. S.; Hannaford, A. J.; Smith, P. W. G.; Tatchell, A. R. (1989), Vogel's Textbook of Practical Organic Chemistry (5th ed.), Harlow: Longman, ISBN 0-582-46236-3
{{VogelQualitative}} Vogel, Arthur I.; Svehla, G. (1979), Vogel's Textbook of Macro and Semimicro Qualitative Inorganic Analysis (5th ed.), London: Longman, ISBN 0-582-44367-9
{{VogelQuantitative}} Mendham, J.; Denney, R. C.; Barnes, J. D.; Thomas, M. J. K. (2000), Vogel's Quantitative Chemical Analysis (6th ed.), New York: Prentice Hall, ISBN 0-582-22628-7

External links[edit]

Avoid adding external links to general sites. Rather, link to the particular article which is relevant. There is absolutely no need to link every national or state regulatory body for a regulated chemical. Instead, use them as inline references in the body of the article, if necessary.

A certain number of frequently used sites have their own templates for the external link. Note that some of these templates need parameters to specify a link to a specific page on the website; read the documentation for the individual template for more details.

Template Link
{{nist}} Linstrom, Peter J.; Mallard, William G. (eds.); NIST Chemistry WebBook, NIST Standard Reference Database Number 69, National Institute of Standards and Technology, Gaithersburg (MD)
{{ICSC|xxyy|xx}} International Chemical Safety Card xxyy
{{inrs}} Institut national de recherche et de sécurité ({{{year}}}). "{{{title}}}." Fiche toxicologique n° {{{number}}}. Paris:INRS. (in French)
{{PubChemLink|xxx}} CID xxx from PubChem
{{GoldBookRef}} IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "{{{title}}}". doi:10.1351/goldbook.{{{file}}}


Interwiki links[edit]

Articles from other WikiProjects[edit]

WikiProject Drugs[edit]

WikiProject Elements[edit]

WikiProject Rocks and Minerals[edit]

WikiProject Polymers[edit]

Other topics[edit]

Capitalization (English language convention)[edit]

The names of chemical compounds are common nouns. They are capitalized at the beginning of a sentence or title, but not elsewhere. The names of chemical elements are also common nouns in English, and are NOT capitalized when written out as words. They retain capitalization as chemical element symbols. There is no more reason to capitalize uranium (symbol U) than carbon (symbol C), or uranium-235 than carbon-14. The convention that elements are common nouns includes even elements derived from proper nouns, such as places or the names of persons. Thus einsteinium (Es) and californium (Cf) are capitalized only in symbol. Please see IUPAC Provisional Recommendations for the Nomenclature of Inorganic Chemistry (2004). The element mercury is not capitalized, but the word when referring to a place (the planet Mercury), the Roman god Mercury, the Ford Mercury automobile, etc., is capitalized as a proper noun.

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... as in isopropanol, 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 1,2-Dichloroethane, which is written as 1,2-dichloroethane if not at the start of a sentence. Note that the two wikilinks refer to separate articles: one is a redirect to the other.

Special symbols[edit]

Greek letters[edit]

The following codes are available for inserting Greek letters into articles. Greek letters are never italicized.

&alpha; α &Alpha; Α
&beta; β &Beta; Β
&gamma; γ &Gamma; Γ
&delta; δ &Delta; Δ
&epsilon; ε &Epsilon; Ε
&zeta; ζ &Zeta; Ζ
&eta; η &Eta; Η
&theta; θ &Theta; Θ
&iota; ι &Iota; Ι
&kappa; κ &Kappa; Κ
&lambda; λ &Lambda; Λ
&mu; μ &Mu; Μ
&nu; ν &Nu; Ν
&xi; ξ &Xi; Ξ
&omicron; ο &Omicron; Ο
&pi; π &Pi; Π
&rho; ρ &Rho; Ρ
&sigma; σ &Sigma; Σ
&tau; τ &Tau; Τ
&upsilon; υ &Upsilon; Υ
&phi; φ &Phi; Φ
&psi; ψ &Psi; Ψ
&chi; χ &Chi; Χ
&omega; ω &Omega; Ω


Various arrows and equillibrium signs cam be added from the "Math and logic" pulldown under the Wikpedia edit window, or copied and pasted from here: → ⇌ ← ⇋ ↔

Other symbols[edit]

  • The center dot for hydrates etc. is available from the code &middot;.
  • The minus sign (longer than a normal hyphen) is available form the code &minus; but does not reproduce well on some versions of Internet Explorer.[which?]
  • The multiplication sign "×" (e.g. for powers of ten) should be used instead of the letter "x".
  • The symbols for Planck's constant, ℎ and ℏ, are available from the codes {{unicode|&#8462;}} and {{unicode|&#8463;}}: the use of the {{unicode}} template is recommended because of a bug in some versions of Internet Explorer.

Chemical structures and reaction schemes[edit]

Please read the structure drawing guidelines page for detailed instruction on drawing and uploading chemical structures, diagrams, and reaction schemes. These guidelines are the consensus agreed to by the structure drawing workgroup.


Use the units employed in the current scientific literature on that topic. This will usually be SI, but not always; for example, theoretical chemists commonly use atomic units, natural units, Debyes, etc.

Values with units should be separated with &nbsp;, and used consistently within the article. Examples include:

  • Diameter of New York: 43 km
  • Surface of a coin: 6.5 cm2
  • Very cold: 263 K or also −10 °C
  • Sirupy: 10 Pa·s
  • Volume: cm3, but not cc

The formal non-SI units accepted for use with SI may be used as well. Examples include:

  • Right angle: 90° (no &nbsp; is used for the angular units °, ′, and ″)
  • Volume: (US spelling article) 5 L for five liters, and (GB spelling article) 5 l or 5 L for five litres
  • Mass: 5 kt/a for annual bulk production of 5 thousand tonnes

It may be appropriate to include conversions in some cases, such as when there is more than one unit in common use or when the commonly-used unit is not well known. For example, kcal/mol and kJ/mol are both commonly used in the literature, so it may be beneficial to readers to include values in both systems. Another common case is pm or nm vs Å.

Chemical reactions[edit]

Chemical reactions in articles should be properly balanced and correct. Formulae in the reactions should not be wikilinked (do that in the introductory text), nor should the atoms in the formulae be wikilinked. Reactions may be numbered for referencing in the text.

The use of phase indication (s), (l), (g), and hydration (aq) should only be used if emphasis on the phase transition in a reaction is intended. Generally, they should be avoided. If used, the first occurrence of the phase indication should be wikilinked. Note that they are not subscripts.

Inorganic reactions and text reactions should be left-aligned, with one indent (wiki-markup ':'). Organic reactions are mostly presented in a graphical way, and treated as images, wrapping around text or centered.

The Bamberger rearrangement

Good examples:

H+(aq) + OH(aq) → H2O(l)
Na2SO4 + H2SO4 ⇌ 2 NaHSO4
  1. Dissolving pure iron in a solution of iron(III) chloride
    Fe(s) + 2 FeCl3(aq) → 3 FeCl2(aq)
  2. Dissolving iron ore in hydrochloric acid
    Fe3O4(s) + 8 HCl(aq) → FeCl2(aq) + 2 FeCl3(aq) + 4 H2O
  3. Upgrading the iron(II) chloride with chlorine
    2 FeCl2(aq) + Cl2(g) → 2 FeCl3(aq)

Bad examples:

Na2SO4(aq) + H2SO4(aq) ⇌ 2 NaHSO4(aq)
H+(aq) + OH(aq) → H2O(l)

See also[edit]


  1. ^ Panico, R.; & Powell, W. H. (Eds.) (1994). A Guide to IUPAC Nomenclature of Organic Compounds 1993. Oxford: Blackwell Science. ISBN 0-6320-3488-2.{{cite book}}: CS1 maint: multiple names: authors list (link)
  2. ^ Leigh, G. J. (Ed.) (1990). Nomenclature of Inorganic Chemistry. Recommendations 1990. Oxford: Blackwell Science. ISBN 0-6320-2494-1.

External links[edit]



Safety information[edit]