If I write a 2000 character answer that has one reference to the molecular formula H2O, is it necessary for this to be changed to $\ce{H2O}$?

Already the above sentence looks a bit weird because the font is all uniform, then suddenly there's a different font.

Should we enforce ChemJax usage here, or is it only appropriate when there's a clear benefit (e.g. for longer chemical formulas, or when the post already contains so much MathJax/ChemJax that whatever disadvantages of using ChemJax are already so heavily present that they don't matter much anymore)?

I'll add a minor note. This question: Check whether a simple molecule is Raman-active or IR-active using PySCF was migrated from Stack Overflow which does not support MathJax in its posts. When migrating away from MMSE, we need to ensure that the target site allows ChemJax or that we've un-done all ChemJax/MathJax that won't be supported on the target site.

  • $\begingroup$ How is different ChemJax from MathJax with mhchem extension? ( $\require{mhchem}$ outside of Chemistry SE where it is active by default, bringing \ce{} and \pu{} ) $\endgroup$
    – Poutnik
    Aug 13, 2022 at 15:34
  • 1
    $\begingroup$ @Poutnik it's not actually called ChemJax, hahaha. I just like calling it that instead of "MathJax with mchem extension". We use it more for the \ce than for math, so it's ChemJax! We also have it on MMSE too (not just Chem.SE). $\endgroup$ Aug 13, 2022 at 15:59
  • $\begingroup$ I think the point below is valid - but certainly if I see H2O or other case in which the subscripts / superscripts aren't formatted, or set in italics, I'm going to add an edit. Generally, the mchem extension helps with search because it still "looks like H2O" to a search engine. $\endgroup$ Dec 30, 2022 at 15:56
  • $\begingroup$ That's a very good point about search engines, I hadn't thought of that! About Italic font, do you meant H2O is okay, but H2O is not? $\endgroup$ Dec 30, 2022 at 16:01

1 Answer 1


For example, if I write a 2000 character answer that has one reference to the molecular formula H2O, is it necessary for this to be changed to $\ce{H2O}$?

In my opinion, no. As long as the chemical formulas in the answer are readable, correct and formatted consistently, I see no reason to edit them. After all, edits are supposed to be substantial and improve the post. Whether or not one considers changing H2O to $\ce{H2O}$ an improvement, it is hard to argue that it is a substantial one. It might also be instructive to recall two common options chosen when reviewing suggested edits (emphasis mine):

  • Approve. This edit clearly improves the post.
  • Reject. The edit does not improve the quality of the post. Changes to the content are unnecessary or make the post more confusing.

On the other hand, I think changing $H_2O$ to H$_2$O or $\ce{H2O}$ is more justified, as the first form is incorrect (individual elements are not variables!). For a simple molecule like water H2O might be fine, but for more complicated ones I think it is clearly beneficial to add subscripts.


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