atomic number 9

Noun

1.

atomic number 9 - a nonmetallic univalent element belonging to the halogens; usually a yellow irritating toxic flammable gas; a powerful oxidizing agent; recovered from fluorite or cryolite or fluorapatite Synonyms: fluorine, F

chemical element, cryolite, element, F, fluor, fluorapatite, fluorine, fluorite, fluorspar, gas, Greenland spar, halogen