If you’re hosting a Chemistry course in Moodle and need to upgrade how you enter and display equations, the Chemistry Editor for Atto might be your solution. The plugin which was adapted by Geoffrey Rowland to enable Chemistry TeX syntax (an extension of MathJax) to be displayed via a filter. According to Mr. Rowland,
The mhchem syntax is fairly intuitive, even for direct text entry. So, the Chemistry editor may act as a useful aid memoir. There are tabs for Formulae (full and ionic equations, isotopes etc), Symbols and units, Bonds and arrows (including equilibria), Greek, Italics and a Periodic table for elements H-Cn together with the lanthanoids and actinoids.
You can download the plugin from Git via this discussion forum: https://moodle.org/mod/forum/discuss.php?d=269149
Or download it from the Moodle.org Plugin Repository: https://moodle.org/plugins/view.php?plugin=atto_chemistry