Gnome Chemistry Utils - The Gnome Chemistry Utils include six chemistry related programs:
ChemDraw - ChemDraw - The Gold Standard for Chemical Structure Drawing and Research Publications.
Kalzium - Kalzium (German for: Calcium) is a periodic table of the elements for KDE SC 4.
ImageJ - and Other Health Care
Avogadro - Avogadro is a free, fantastically easy to use molecule editor.
Periodic-table.io - Interactive periodic table of the chemical elements in 38 languages - Includes properties, history, name origin, facts, applications, hazards, isotopes and more