5.3 KiB
created, up, title, source, author, published, topics, tags
| created | up | title | source | author | published | topics | tags | |
|---|---|---|---|---|---|---|---|---|
| 2026-01-21T22:39:55 |
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mhchem for MathJax, mhchem for KaTeX | https://mhchem.github.io/MathJax-mhchem/ |
mhchem is a tool for writing beautiful chemical equations easily.
This is the manual for mhchem’s input syntax (as implemented in JavaScript display engines for mathematics).
Chemical Equations (ce)
\ce{CO2 + C -> 2 CO}
\ce{CO2 + C -> 2 CO}
\ce{Hg^2+ ->[I-] HgI2 ->[I-] [Hg^{II}I4]^2-}
\ce{Hg^2+ ->[I-] HgI2 ->[I-] [Hg^{II}I4]^2-}
Chemical Formulae
Charges
Stoichiometric Numbers
Nuclides, Isotopes
It might be ambiguous whether a superscript belongs to the left or right element. There is automatic detection (digits only = mass number = belongs to right side), but to make sure you can type {} as a separator.
Reaction Arrows
not to be used according to IUPAC and ACS
Each arrow can take two optional arguments: one for above and one for below. The arrow arguments use the same input syntax as the \ce command.
$\ce{
upright text, see below
$\ce{
italic math, see below
Unfortunately, MathJax cannot stretch <-->, <=>, <=>> and <<=> arrows properly. All the arrows do stretch in LaTeX and KaTeX.
Parentheses, Brackets, Braces
Use parentheses ( ) and brackets [ ] normally. Write braces as \{ \}.
For large parentheses, \left and \right macros need to be in the same math environment, so you might have to put \ce into $ into \ce, but that’s fine.
$\ce{
States of Aggregation (not fully supported for LaTeX yet)
not IUPAC-conform, not ACS-conform
Crystal Systems (not fully supported for LaTeX yet)
Variables like x, n, 2n+1**
Typographical conventions say that variables are typeset in an italic font, while other entities (like chemical elements) are typeset in an upright font. mhchem tries to recognize common patterns and use the correct (italic) font, like the x and n in the following examples.
$\ce{
If a more complex term is not properly recognized, you can switch to math mode (= italics) explicitly.
Greek Characters
Just write \alpha etc. Typographical conventions say that variables are typeset in an italic font, while other entities (like chemical elements) are typeset in an upright font. In the following examples, the Greek character is not a variable that stands for a number, therefore an upright font should be used. Unfortunately, neither MathJax nor KaTeX support upright lower-case Greek characters.
$\ce{
Spaces after a greek character are ignored. This is standard TeX behavior. Insert {} to get the desired output.
$\ce{
(Italic) Math
By using $...$ you can escape to math mode.
$\ce{
(With mhchem for LaTex there is a difference between $...$ and ${...}$. But because neither MathJax nor KaTeX have a text font, both inputs will yield identical results there.)
Italic Text
With the same mechanism you can mimic an italic text font.
$\ce{
Spaces will be ignored. Use a ~ when you need to typeset a space.
Upright Text, Escape Parsing
Enclose upright text with {...}.
$\ce{
With the same mechanism, you can escape parsing, for instance if you need a simple hyphen (that should not become a bond).
$\ce{
Bonds
mhchem tries to differentiate whether \ce{-} should be a bond, a charge or a hyphen.
$\ce{
$\ce{
$\ce{
$\ce{
$\ce{
$\ce{
Addition Compounds
$\ce{
Oxidation States
$\ce{
Unpaired Electrons, Radical Dots
Kröger-Vink Notation (not supported for LaTeX yet)
$\ce{
$\ce{
upright V = Vanadium, italic V = vacancy
Equation Operators
not to be confused with bonds
not to be confused with bonds
Precipitate and Gas
$\ce{
$\ce{
Other Symbols and Shortcuts (not fully supported for LaTeX yet)
Complex Examples
$\ce{
$\ce{
$\ce{
$\ce{
Physical Units (pu) (MathJax or KaTeX only, not for LaTeX)
There are two conventions regarding the multiplication within units.
There are four conventions regarding divisions.
There are four main conventions for writing numbers in scientific notation.
If you need more control than is offered here, take a look at the siunitx extension.
Compatibility with mhchem for LaTeX
Most of these examples work identically for mhchem for MathJax, mhchem for KaTeX and mhchem and LaTeX. Exceptions are indicated. Also, some edge-cases may render differently. I will try to minimize the differences in the future. But even then, the MathJax and KaTeX versions will always be more tolerant of sloppy input (e.g. a missing space) than mhchem for LaTeX.
Contact and Support
If you have a question and cannot find an answer—neither here nor with a web search—then
- mail me (mhchem@MartinHensel.de) or
- create an GitHub issue (https://github.com/mhchem/MathJax-mhchem/issues) or
- ask at StackExchange (http://meta.chemistry.stackexchange.com/) with the mhchem tag.