Fluorine
Fluorine is a halogen group element known by the atomic symbol F. Its atomic number is 9, and its atomic weight is 18.998. It has a melting point of -363.3 °F (-219.6 °C), a boiling point of -306.6 °F (-188.1 °C), and typically occurs as a pale yellow, diatomic gas.
It is the most reactive of all elements and combines, often violently, with nearly all other elements. Even a compound such as water will burn with a bright flame in an atmosphere of fluorine gas. Many of the element's compounds are toxic and can cause deep, severe burns on contact. Yet fluorine exists in many harmless compounds as well. Most of it occurs in the mineral fluorspar, which is found throughout the world. In the United States, Illinois produces more than half the nation's fluorspar. Fluorine is also a constituent of the mineral cryolite, which is found in commercial quantities only in Greenland.
Fluorine possesses the smallest and lightest atoms of the halogen family, a group of elements that readily combines with metals to form salts. The element reacts with most inorganic compounds to form fluorides such as uranium hexafluoride. This compound, which is used to prepare uranium for atomic bombs and nuclear reactors, became important during World War II and spawned the commercial fluorine production industry.
The isolation of fluorine, one of the most reactive and dangerous elements known, was accomplished only after 75 years of continuing effort by scientists. At the turn of the nineteenth century, Sir Humphry Davy, who pioneered in the use of electrolysis to discover new elements, observed similarities between hydrogen chloride and hydrogen fluoride, which Karl Scheele had discovered in the 1770s. Deducing that the element fluorine must exist, Davy tried unsuccessfully to decompose hydrogen fluoride by using electrolysis and was poisoned as a result. In a similar experiment, Scottish scientist Thomas Knox suffered from inhaling toxic gas. Another investigator, Paulin Lauyet, died while trying to isolate fluorine.
In the 1870s French chemist Edmond Fremy (1814-1894), who was working with a number of fluoride compounds, came close to taming the element. Although Fremy's repeated attempts to isolate fluorine were unsuccessful, he laid the groundwork for his student, French chemist Ferdinand Frederic Henri Moissan (1852-1907). Moissan, who grew up in poverty, worked his way through college and was able to devote himself to scientific pursuits only through the financial support of his father-in-law. In 1886, Moissan succeeded in isolating fluorine, a pale yellow gas, by decomposing hydrogen fluoride electrolytically. The secret to his success, where so many others had failed, was the platinum-iridium alloy he used for his apparatus, which resisted attack from fluorine. Moissan also chilled the electrolytic solution to reduce the element's reactivity. In 1906, he won the Nobel Prize in part for his research on fluorine.
Since the turn of the century, scientists have developed techniques for handling fluorine safely and transporting it as a liquid. Today 's methods of manufacturing fluorine on a commercial scale are essentially variations of the process used by Moissan. Since World War II, fluorine and its compounds have been used in many industrial applications. For example, hydrofluoric acid is used to etch glass for products such as light bulbs. The oil industry uses hydrogen fluoride as a catalyst to increase the octane number of gasoline. Fluorine is also a constituent of polymers such as Teflon that are used to coat frying pans and other products. And the chemical industry uses crystals of calcium fluoride to analyze compounds by bending and focusing infrared light onto them.
Fluorine-containing compounds called CFCs (chlorofluorocarbons) have traditionally been used in refrigerators, air conditioners, and aerosol sprays. But these compounds have been linked to the depletion of the Earth's protective ozone layer, and their use is being phased out. Perhaps the most familiar form of the element is the compound stannous fluoride, a combination of fluorine and tin, which is used in toothpastes and dental treatments to prevent tooth decay. Fluoride, as it is better known, has also been added to the drinking water of several communities throughout the United States.
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