Wikipedia:Manual of Style (chemistry)

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This guideline is a part of the English Wikipedia's Manual of Style. Use common sense in applying it; it will have occasional exceptions. Please ensure that any edits to this page reflect consensus.

Shortcuts: WP:MOS (chemistry) WP:MOSCHEM WP:CHEMMOS

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Manual of Style for chemistry articles

Article titles Chembox Chemicals Compound classes InChI Nav. templates Nomenclature Structure drawing Safety Reactions Refs./Ext. links Ref. templates

This document aims to be brief, touching on the general aspects of chemistry-related articles. In-depth guides are found in the relevant sub-pages.

Contents 1 Scope 2 General 2.1 Nomenclature 2.2 Structure drawing 2.3 Safety 2.3.1 Toxicology 2.4 Current events 2.5 References and external links 3 Article types 3.1 Compounds 3.2 Compound classes 3.3 Reactions 3.3.1 Line equations 3.3.2 Sectioning 4 Other issues 4.1 Nuclear chemistry 4.2 Laboratory/industrial apparatus and equipment 4.3 Analytical techniques 4.4 Chemists 4.5 Safety sections

[edit] Scope

Since Wikipedia is an encyclopedia, not all articles are suitable for inclusion, see WP:NOTABILITY. The field is so large that it is not reasonable to anticipate the full range of coverage, but important topics include compounds, reactions, methods of analysis, instrumentation/apparatus, techniques, significant chemists, branches of chemistry, and theories and principles.

[edit] General

[edit] Nomenclature

Per WP:ENGVAR, the type of English used to write the articles does not matter, but it should be consistent. The following exceptions apply for chemical names:

• "sulfur" (and related "sulfuric", etc)., "caesium", and "aluminium" should be spelled this way regardless of the English variation used in the article, being the IUPAC names for these elements
• "phosphine" is preferred over "phosphane", being predominantly used in the chemical literature

Systematic nomenclature, while being precise, can be cumbersome. Commonly accepted trivial or alternative names are preferred over systematic names. In particular, IUPAC recommends the use of non-systematic names for some organic compounds, and these recommendations should be followed in article titles.[1] Examples include acetic acid over ethanoic acid, toluene over methylbenzene, lysine over 2,6-diaminohexanoic acid.

Stock nomenclature (e.g. iron(III) chloride: there should be no space between the words and the oxidation state in parentheses (between "iron" and (III)). The oxidation numbers are stated only for cations, not for anions. Where the oxidation number is obvious, it is not included. Compounds with a substantial degree of covalency do not use Stock nomenclature.

Isotopes should be labelled by their mass number, e.g. ¹⁴C and ¹⁸F. Deuterium and tritium may be labelled "D", "²D", or "²H" and so on. Deuterated solvents for NMR use are customarily described variously as: CD₃OD, methanol-d₄; CD₃SOCD₃, DMSO-d₆. These established systems are all acceptable, but should remain consistent within an article.

For organic radicals denoted by "R", indices used for numbering must be superscript: R¹-CH₂-R² (not R₁-CH₂-R₂).

[edit] Structure drawing

Appropriate formats are PNG and SVG. ACS settings have been adopted as the convention. Images should be legible at 450 pixels wide, to avoid interference from the chembox on the right.

Hydrogens should be implied (hidden), except for the benefit of the target audience. The use of Me to denote methyl may be confusing. The use of Et, Pr, etc., is discouraged. When Ph is used to denote phenyl and X for halogen or any atom, it should be clearly defined within the image.

[edit] Safety

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.

[edit] Toxicology

Depending on the extent and nature of the information, toxicological 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.

[edit] Current events

From WP:NOT#JOURNALISM:

Journalism. Wikipedia should not offer first-hand news reports on breaking stories. Wikipedia is not a primary source. However, our sister project Wikinews does exactly that, and is intended to be a primary source. Wikipedia does have many encyclopedia articles on topics of historical significance that are currently in the news, and can be updated with recently verified information.

Accidents and incidents occur all the time. While their scale and magnitude may merit inclusion in Wikipedia on grounds of notability, that such an accident has occurred is not sufficient justification for inclusion in the context of an article about chemicals. Wikipedia does not attempt to dispense advise on what to do in the event of a (...) incident, either. (See WP:NOTGUIDE) Historic accidents and incidents may only be contextualized in the discussion on the specific hazards of certain chemicals, without serving as case studies in itself. To reiterate, if such accidents are sufficiently notable, they should have their own article (e.g. discussion in Bhopal disaster, not in methyl isocyanate).

[edit] References and external links

See /References and external links

[edit] Article types

[edit] Compounds

All articles on chemicals, real or hypothetical, should have a Chembox. Formula should be readily available, variables like n, x, or y are permissible for substances of variable composition such as polymers. For compounds of defined composition, the molar masses should be available as well. The article should cover these aspects as appropriate:

• Introductory paragraph (WP:lede)
• Properties
• Occurrence
• Preparation
• Uses and/or reactions
• History
• Safety
• Toxicology
• Suppliers should not be listed unless the compound is rare and only available from one or two suppliers
• References

[edit] Compound classes

These articles belong to one of these categories:

• monoatomic ions (chloride, bromide; oxide, sulfide)
• polyatomic ions (nitrates, perchlorates, triflates, tetrafluoroborates)
• functional groups (alcohols, aldehydes, acids, nitriles)
• "backbone" moieties, both organic and inorganic
  • steroids, aldohexoses, terpenes
  • metal oxo compounds, metal carbonyl compounds, metal clusters

Where a compound class does not have sufficient detail to merit a full article, it should be merged to the parent article (usually that of the acid). Articles discussing compound classes should be clearly distinguished from the compound for which the class is named. An example is quinoline versus quinoline (compound class).

Aspects to be covered include:

• Nomenclature
• Structure and bonding
• Properties
• Characterization
• Applications
• Occurrence
• Preparation
• Reactions
• History
• Safety

[edit] Reactions

Simple reactions can be typed out in text. Separate the number of molecules from the molecule symbol by a space (i.e 3 H₂ instead of 3H₂). Reactions should be indented with a colon (:), and not centered. This applies for reactions in the form of images as well. For example:

2 Na + 2 H₂O → 2 NaOH + H₂

Although many organometallic reagents have complex structures involving solvation or clusters, these reagents are ordinarily depicted in simplified structures (RMgX with two-coordinate Mg, BuLi with one coordinate Li, etc). To facilitate sharing of drawings between different language wikis, reagents above and below arrows should consist of formulas, not words.

[edit] Line equations

Avoid the use of <math> notation: the existing character set is adequate to enter reaction data; the change in size and font from is very jarring to the reader. Ionic equations are preferred. State symbols are omitted unless they are relevant (e.g. thermochemistry, to illustrate precipitation for chemical separation). "Heat" should not be a reaction product; stating ΔH_r, or giving its sign is preferable:

C₂H₅OH (g) + 3 O₂ (g) → 2 CO₂ (g) + 3 H₂O (l) (ΔH_r = −1409 kJ/mol)

Instead of:

C₂H₅OH (g) + 3 O₂ (g) → 2 CO₂ (g) + 3 H₂O (l) + heat

Compounds and/or atoms should not be wikilinked in the reaction. These links should be in the surrounding text.

[edit] Sectioning

Each reaction article should include the following sections:

• A brief overview

This section should include a broad description of the reaction in both text and reaction scheme. Please include references to review articles and key references.

• Reaction mechanism

The reaction mechanism should include a reaction scheme, which is described in the accompanying text. Non-obvious statements should be referenced.

• Scope (optional)

Reaction details such as temperature requirements, order of addition, or side reactions can be included.

• Variations (optional)

If one can vary the outcome of the reaction by small changes, such descriptions should go in this section.

• See also (optional)

This is a nice place to put related reactions that are not mentioned in the above text.

• References

This entire section should only be the following text:

==References==
{{reflist}}

Additional notes:

• Reaction schemes are best aligned left without borders as follows:

[[Image:Horner-Wadsworth-Emmons_Reaction_Example.png|350px|The Horner-Wadsworth-Emmons reaction]]

Result being:

(Taken from the Horner-Wadsworth-Emmons reaction, which is a good example of a quality organic reaction article.)

• Please become familiar with the reaction category heirarchy and categorize the article appropriately.
• Please upload all images to Wikimedia Commons, so other language Wikipedias can use the same images.

[edit] Other issues

The following sections are excluded from the March 2009 ratification of this style guide.

[edit] Nuclear chemistry

Nuclear reactions should follow the same convention as regular chemical reactions, but the isotope and element number should always be specified using {{Nuclide}}. {{SubatomicParticle}} and {{PhysicsParticle}} can be used to write the symbols for subatomic particles. For example, the beta decay of carbon-14 should be written as:

146C → 147N + e⁻ + ν_e

[edit] Laboratory/industrial apparatus and equipment

A description of the function and the design of the piece. References tend to come in the form of product brochures and catalogs. Niche items should be mentioned in the next larger set.

[edit] Analytical techniques

Principles behind these techniques should be used. For example, atomic absorption spectroscopy should describe spectral lines; NMR spectroscopy should describe the spin of nuclei. Simple calculations may be used to illustrate certain concepts; detailed calculations should be omitted.

[edit] Chemists

• Nobel prize winners
• People who have a reaction named after them
• etc. etc.

See notability for people

[edit] Safety sections

The general principle is that safety sections should only be use when they add something to an article, and should be based (where at all possible) on peer-reviewed or otherwise highly reliable sources.