Science / Periodic Table of Elements / Fluorine (F): Atomic number: 9, Atomic mass: 18.998403 g.mol -1, Electronegativity: 4, Density: 1.8*10-3 g.cm-3 at 20°C, Melting point: -219.6 °C, Boiling point: -188 °C, Vanderwaals radius: 0.135 nm, Ionic radius: 0.136 nm (-1) ; 0.007 (+7), Isotopes: 2, Electronic shell: [ He ] 2s22p5, Energy of first ionisation: 1680.6 kJ.mol -1, Energy of second ionisation: 3134 kJ.mol -1, Energy of third ionisation: 6050 kJ mol-1, Standard potential: - 2.87 V, Discovered by: Moissan in 1886. 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. Fore more information visit our page on mineral water. Fluorine in the environment: Annual world production of the mineral fluorite in around 4 million tonnes, and there are around 120 million tonnes of mineral reserves. The main mining areas for fluorite are China, Mexico and Western Europe. Fluorine occurs naturally in the earth's crust where it can be found in rocks, coal and clay. Fluorides are released into the air in wind-blown soil. Fluorine is the 13th most aboundant element in the Earth's crust: 950 ppm are contanined in it. Soils contain approximatively 330 ppm of fluorine, ranging from 150 to 400 ppm. Some solis can have as much as 1000 ppm and contaminated solis have been found with 3500 ppm. Hydrogen fluorides can be released into air through combustion processes in the industry. Fluorides that are found in air will eventually drop onto land or into water. When fluorine is attached to very small particles it can remain in the air for a long period of time. In the atmosphere 0.6 ppb of fluorine are present as salt spray and organicochloride compounds. Up to 50 ppb has been recorded in city environments.
Science / Tides and Currents / Node Factor (F): A factor depending upon the longitude of the Moon's node which, when applied to the mean coefficient of a tidal constituent, will adapt the same to a particular year for which predictions are to be ma MORE
Science / Periodic Table of Elements / Fluorine (F): Atomic number: 9, Atomic mass: 18.998403 g.mol -1, Electronegativity: 4, Density: 1.8*10-3 g.cm-3 at 20°C, Melting point: -219.6 °C, Boiling point: -188 °C, Vanderwaals radius: 0.135 nm, Ionic radi MORE