When MathType is used with the chemistry toolbar we shall refer to it as ChemType. The scope of ChemType is limited to chemistry formulas that can be encoded with MathML.
MathType APPs and MathType Integrations do typically include two icons for MathType, one for the generic math toolbar and another for ChemType.

In mathematical notation, variable names are typically presented in italics. For chemical elements, this is not the expected behavior. In ChemType, elements appear as upright (Roman) letters.
The main tab of ChemType includes the most useful symbols to create chemical notation. The other tabs and icons in the toolbar are the same as in MathType.

Even if ChemType is not loaded, you can find some chemistry-related symbols in MathType's main tabs. For example, you can find arrows for reactions in MathType's Arrows tab.

There are symbols for chemical elements in MathType's Greek, letters, and numbers tab. The most frequent symbols are on display, and all others are in an extra section, arranged in a periodic table.
