Crossword clues for fluorine
Longman Dictionary of Contemporary English
The Collaborative International Dictionary
Fluorine \Flu"or*ine\ (fl[=u]"[o^]r*[i^]n or fl[=u]"[o^]r*[=e]n; 104), n. [NL. fluorina: cf. G. fluorin, F. fluorine. So called from its occurrence in the mineral fluorite.] (Chem.) A non-metallic, gaseous element of atomic number 9, strongly acid or negative, and associated with chlorine, bromine, and iodine, in the halogen group of which it is the first member. It always occurs combined, is very active chemically, and possesses such an avidity for most elements, and silicon especially, that it can neither be prepared nor kept in glass vessels, but may be contained in lead vessels. If set free it immediately attacks a containing glass vessel, so that it was not isolated until 1886. It is a pungent, corrosive, colorless gas. Symbol F. Atomic weight 19.00.
Note: Fluorine unites with hydrogen to form hydrofluoric acid, which is the agent employed in etching glass. It occurs naturally, principally combined as calcium fluoride in fluorite, and as a double fluoride of aluminium and sodium in cryolite.
Douglas Harper's Etymology Dictionary
n. 1 (context uncountable English) The chemical element (''symbol'' F) with an atomic number of 9. 2 (context chemistry countable English) A fluorine atom.
n. 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 [syn: F, atomic number 9]
Fluorine is a chemical element with symbol F and atomic number 9. It is the lightest halogen and exists as a highly toxic pale yellow diatomic gas at standard conditions. As the most electronegative element, it is extremely reactive: almost all other elements, including some noble gases, form compounds with fluorine.
Among the elements, fluorine ranks 24th in universal abundance and 13th in terrestrial abundance. Fluorite, the primary mineral source of fluorine, was first described in 1529; as it was added to metal ores to lower their melting points for smelting, the Latin verb meaning "flow" became associated with it. Proposed as an element in 1810, fluorine proved difficult and dangerous to separate from its compounds, and several early experimenters died or sustained injuries from their attempts. Only in 1886 did French chemist Henri Moissan isolate elemental fluorine using low-temperature electrolysis, a process still employed for modern production. Industrial production of fluorine gas for uranium enrichment, its largest application, began during the Manhattan Project in World War II.
Owing to the expense of refining pure fluorine, most commercial applications use fluorine compounds, with about half of mined fluorite used in steelmaking. The rest of the fluorite is converted into corrosive hydrogen fluoride en route to various organic fluorides, or into cryolite which plays a key role in aluminium refining. Organic fluorides have very high chemical and thermal stability; their major uses are as refrigerants, electrical insulation and cookware, the last as PTFE (Teflon). Pharmaceuticals such as atorvastatin and fluoxetine also contain fluorine, and the fluoride ion inhibits dental cavities, and so finds use in toothpaste and water fluoridation. Global fluorochemical sales amount to more than US$15 billion a year.
Fluorocarbon gases are generally greenhouse gases with global-warming potentials 100 to 20,000 times that of carbon dioxide. Organofluorine compounds persist in the environment due to the strength of the carbon–fluorine bond. Fluorine has no known metabolic role in mammals; a few plants synthesize organofluorine poisons that deter herbivores.
Usage examples of "fluorine".
Actually, that makes sense: neutrons decaying into protons and pions would transmute some of the calcium to scandium, the oxygen to fluorine, and the carbon to nitrogen.
The more outrŽ science-fictional speculations about extraterrestrial biochemistries—silicon in place of carbon, chlorine or fluorine in place of oxygen, and so forth—were all very clever, but for various reasons they just didn't work.
To cite one case, a steroid that differs from the natural corticoids in possessing a fluorine atom attached to carbon-g is an unusually active glycocorticoid, ten times as active as the natural ones.
A few hours later, the somewhat chastened scientist admitted that he had also found two bottles of elemental fluorine, used to power the lasers which could zap passing celestial bodies at thousand-kilometre ranges for spectrographic sampling.
It sometimes appears combined with fluorine in chlorine trifluoride.
Polyvinylidene difluoride was a special polymer in that respect—carbon atoms were linked to hydrogen and fluorine atoms in such a way that the resulting substance was even more piezoelectric than quartz.
But there are abundant microbes on Zaranai that metabolize fluorides and release fluorine gas as a waste product.
Lithium five doesn't exist on Earth, or glucinium eight, or nitrogen fifteen or 'oxygen seventeen or fluorine eighteen or sulphur thirty-four - or thirty-five!
Even the halogens were still frozen across its flat top, thousands of square miles of fluorine ice with near-vacuum above.
Some other molecules--hydrogen fluoride, for example--might approach water in their ability to dissolve other molecules, but the cosmic abundance of fluorine is extremely low.
As pure fluorine was about the most vicious substance known to man, it was high on the list of prohibited materials - but, like the rockets which drove the penetrometers down to their targets, it was essential for the mission.