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Fluorine is an univalent poisonous gaseous halogen, it is pale yellow-green and it is the most chemically reactive and electronegative of all the elements. Fluorine readily forms compounds with most other elements, even with the noble gases krypton, xenon and radon. It is so reactive that glass, metals, and even water, as well as other substances, burn with a bright flame in a jet of fluorine gas. In aqueous solution, fluorine commonly occurs as the fluoride ion F-. Fluorides are compounds that combine fluoride with some positively charged counterpart. == Applications == Atomic fluorine and molecular fluorine are used for plasma etching in semiconductor manufacturing, flat panel display production and MEMs fabrication. Fluorine is indirectly used in the production of low friction plastics such as teflon and in halons such as freon, in the production of uranium. Fluorochlorohydrocarbons are used extensively in air conditioning and in refrigeration. Fluorides are often added to toothpaste and, somewhat controversially, to municipal water supplies to prevent dental cavities. Fluorine-18 (18F) is a fluorine radioisotope which is an important source of positrons. It has a mass of 18.0009380(6) u and its half-life is 109.771(20) minutes. It decays by positron emission 97% of the time and electron capture 3% of the time. Both modes of decay yield stable oxygen-18. Fluorine-18 is an important isotope in the radiopharmaceutical industry, and is primarily synthesized into fluorodeoxyglucose (FDG) for use in positron emission tomography (PET scans). It is substituted for hydroxyl and used as a tracer in the scan. Its significance is due to both its short half-life and the emission of positrons when decaying. In the radiopharmaceutical industry, it is made using either a cyclotron or linear particle accelerator to bombard a target, usually of pure or enriched oxygen-18-water 〔Fowler J. S. and Wolf A. P. (1982) The synthesis of carbon-11, fluorine-18 and nitrogen-13 labeled radiotracers for biomedical applications. Nucl. Sci. Ser. Natl Acad. Sci. Natl Res. Council Monogr. 1982.〕 with high energy protons (typically ~18 MeV protons). Fluorine also has many uses in Daltons theory of atoms. Fluorine-18 is often substituted for a hydroxyl group in a radiotracer parent molecule, due to similar steric and electrostatic properties. This may however be problematic in certain applications due to possible changes in molecule polarity. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Fluorine-18」の詳細全文を読む スポンサード リンク
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