• noun a yellowish gas
  • A chemical element whose atomic number is 9. It is a pale yellow diatomic gas which is poisonous and highly corrosive. It is the most electronegative element, and among the nonmetallic elements is the most reactive. It reacts spontaneously and vigorously with most elements, thus it is never found uncombined in nature. It has about 10 known isotopes, of which one is stable. Fluorine has various applications, including its use in ceramics, glass etching, low-friction materials, and lasers. It is a halogen, and its chemical symbol is F.

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