Fluorine is a chemical element known by the chemical symbol F. It is classified as a halogen in the periodic table. It is perhaps best known as the most electronegative element, which as a result will readily react with other elements to form various compounds. The acid states of the element are quite dangerous and chemists must treat work containing fluorine very carefully. The element is quite useful to the human population and is used in a variety of ways. Most people will be familiar with fluoride. The chemical is added to dental products like toothpaste and mouthwash to prevent tooth decay. In many areas, including the US, water goes through a fluoridation process which adds the chemical to drinking water.
At room temperature, fluorine forms gaseous diatomic molecules. Diatomic molecules are molecules made up of two atoms; these atoms can be different or the same and in fluorine's case they are the same. At this gaseous state, fluorine's density is about 1.3 times that of air's. Fluorine gas appears to the human eye as both yellow-green and pale yellow; the appearance somewhat depends on how the gas is contained when one views it. The halogen's odor has been described as pungent; this odor can be noticed in concentrations as low as 20 ppb (parts per billion). At -188 degrees Celsius, or -377 degrees Fahrenheit, fluorine will condense into a bright yellow liquid. The condensing temperature is similar to those of oxygen and nitrogen. At -220 degrees Celsius, or -363 degrees Fahrenheit, Fluorine solidifies into beta-fluorine, which is a cubic structure. In this structure the fluorine is soft and transparent; there is also significant molecular disorder. At even colder temperatures, -228 degrees Celsius or -378 degrees Fahrenheit, fluorine becomes a monoclinic structure known as alpha-fluorine. This change is a solid-solid phase transition and the alpha-fluorine is opaque and hard, full of layers filled with close packed molecules. This transition needs more energy than the other transitions and can create violent explosions. The solid state of fluorine is related more to oxygen's than other halogens'.   
Though fluorine is an abundant mineral on earth, coming in as the thirteenth most common element in the crust, it is never occurs as a free element. The element always occurs in compounds because of its high electronegativity. Fluorite or fluorspar (CaF), fluorapatite (Ca5(PO4)3F), and cyrolite (Na2AF6) are the three most well known and most frequently occurring compounds containing fluorine. Along with these compounds, topaz also contains fluorine. Cosmology suggests that fluorine is somewhat rare in the universe. It is said that there are 400 ppb (parts per billion). If any fluorine is produced in stars, nuclear fusion quickly eradicates it. Because of the only temporary existence in some stars, it is difficult to determine clearer data regarding fluorine in space. Fluorine in space is known to combine with hydrogen, making hydrogen fluoride.  
One of fluorine's main uses is the production of uranium. Fluorine and its compounds are used to produce many other chemicals including some strong plastics. In drinking water, sodium fluoride can be harmful if it is at a 2 ppm level. Mottled tooth enamel, skeletal fluorosis, cancer, and other diseases may be caused by fluoride. On the other hand, fluoride in toothpastes and mouthwashes (topically applied fluoride) may aid in reducing dental problems. 
Fluorine that is utilized for commercial purposes mainly comes from fluorite. China leads fluorite production; the US was a large producer but closed down its last mine in Illinois in 1995 because of harmful effects on the ozone layer. In 2002, China produced fifty-four percent of the world fluorite production which equaled about 2.45 million tons (world total was 4.51 million tons). There are two different grades of fluorite or fluorspar: acid grade and metallurgical grade. In 2002, fluorspar consumption was 588,000 metric tons. About 91% of this was acid grade and about 9% was metallurgical grade. Acid grade fluorspar is mainly purposed for the making of hydrofluric acid (HF) and aluminum flouride (AlF3). Uses for hydrofluric acid include manufacturing of various chemicals that are utilized in refrigerants, foam-blowing agents, solvents, and the production of high-performance plastics. Aluminum fluoride is utilized in the smelting of aluminum. The compound is added to molten batches of cyrolite and fluorspar to cool down the operating temperature and to hold back the production of unwanted sodium that harms production efficiency. The other, less popular metallurgical grade fluorspar is used as a flux for steel-making and in cements, enamels, glass and fiberglass, and welding rod coatings. 
Fluorine is also used in the treatment of water. The US government claims that fluoridation of water prevents tooth decay. Though the fluoridation of water has been going on for over sixty-five years, many people strongly oppose the process. They do not want the chemical being put in their water. It is generally regarded as a beneficial process but the issue is not cut and dry. 
Discovery of Fluorine
Georgius Agricola, a German mineralogist, described the use of mineral fluorspar in the metal refining process. The year was 1520 and the compound was already being utilized for production efficiency. Fluorspar helped metal refiners by allowing pure metal to be collected without the unwanted metal ores. It bound to this junk ore, letting the valuable material be obtained easier. Though fluorine had not truly been discovered, the compound was called fluorspar due to the Latin word "fluere" which means 'to flow.' In turn, the name fluorine would be derived from this word and the same Latin root. Gay Lussac, Louis Jacques Thenard, Humphry Davy, Carl Wilhelm Scheele, and Joseph Priestley all worked on experiments with fluorspar in the early 1800s. The common result of their experiments was the highly dangerous hyrdrofluoric acid, or what they called fluoric acid. The acid is so deadly that even a small splash on skin could prove fatal. When chemists tried to isolate fluorine, they were sometimes blinded or killed. The famous English chemist Humphry Davy once stated, “[fluoric acid] is a very active substance, and must be examined with great caution." Frenchmen Andre-Marie Ampere hypothesized that fluoric acid was a compound that contained hydrogen and some other, unknown element. He corresponded with Davy and in 1813 Humphry announced his discovery of fluorine. Davy wrote, “… it appears reasonable to conclude that there exists in the fluoric compounds a peculiar substance, possessed of strong attractions for metallic bodies and hydrogen… it may be denominated fluorine, a name suggested to me by M. Ampere.” In 1886, the element was at last isolated by French chemist Henri Moissan. Moissan was severely affected by poison four times during his dangerous work. But the hard work paid off and in 1906 the Frenchman won the Nobel Prize in Chemistry. 
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