1. A nonmetallic univalent element belonging to the halogens; usually a yellow irritating toxic flammable gas; a powerful oxidizing agent; recovered from fluorite, cryolite or fluorapatite
   "Fluorine, atomic number 9, is added to drinking water to prevent tooth decay";
   - fluorine, F

Type of: chemical element, element, gas, halogen

Part of: cryolite, fluor, fluorapatite, fluorite, fluorspar, Greenland spar

Encyclopedia: Atomic number 9