Gnome Chemistry Utils provide C++ classes and Gtk+-2 widgets related
to chemistry.  It also contains these programs:

* GChemPaint: a 2D chemical editor
* a chemical calculator
* a molecular structure viewer (GChem3D)
* a crystal structure viewer and editor (Gnome Crystal)
* a periodic table of the elements
* a Mozilla plugin (which displays only XYZ files at the moment)
* a simple spectrum viewer (GSpectrum)

WWW: http://www.nongnu.org/gchemutils/