Chemistry editor plugin for Atto text editor, which is maintained by Geoffrey Rowland has been updated to a new version v2.9-1 which supports Moodle 2.7 to 2.9.
Chemistry Editor plugin for Atto allows you to edit chemistry equations in Moodle 2.7, or later, using the mhchem extension to the MathJax or TeX filter. Useful for full and ionic equations, isotopes, equilibrium reactions, thermochemistry and reaction kinetics. Includes a periodic table of element symbols.
You can download the latest version of the Chemistry editor plugin from the Moodle plugins database here: https://moodle.org/plugins/view/atto_chemistry
More information about using the Chemistry Editor plugin can be found here: https://docs.moodle.org/29/en/Chemistry_notation_using_mhchem