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radon
Columbia Encyclopedia entry: radon
Radonrā'dŏn, gaseous radioactive chemical element; symbol Rn; at. no. 86; mass no. of most stable isotope 222; m.p. about -71°C; b.p. -61.8°C; density 9.73 grams per liter at STP; valence usually 0. Radon is colorless and the most dense gas known. Chemically unreactive, it is classed as an inert gas in Group 18 of the periodic table. Synthesis of radon fluoride has been reported. Radon is highly radioactive and has a short half-life. The chief use of radon is in the treatment of cancer by radiotherapy. It has also found some use (mixed with beryllium) as a neutron source. All naturally occurring radon decays by the emission of alpha particles. The element is found in some spring waters, in streams, and to a very limited extent (about 1 part in 1021) in air. Radon is produced by the disintegration of its precursors in minerals, from which it diffuses in small amounts. In homes and other buildings in some areas of the U.S., radon produced by the radioactive decay of uranium-238 present in soil and rock can reach levels regarded as dangerous, but the seriousness of the problem is unclear. Twenty isotopes of radon are known, but only three occur naturally. Radon-222 (half-life 3.82 days) is produced by the decay of radium-226. Radon-220 (half-life 55 sec), also called thoron, is produced in the decay series of thorium-232. Radon-219 (half-life 4 sec), also called actinon, is produced in the decay series of uranium-235 (actinouranium). Ernest Rutherford discovered thoron in 1899. F. O. Dorn discovered radon-222 in 1900 and called it radium emanation. In about 1902, F. O. Giesel discovered actinon. In 1908 William Ramsay and R. W. Whytlaw-Gray isolated the element, which they called niton, and studied its physical properties. The name radon was adopted in the 1920s to refer to all the isotopes of the element, although the name emanation and symbol Em are sometimes used.

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Wikipedia search results for: Radon
From Wikipedia, the free encyclopedia
Radon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas, occurring naturally as the decay product of radium. It is one of the densest substances that remains a gas under normal conditions and is considered to be a health hazard due to its radioactivity. Its most stable isotope, 222 Rn, has a half-life of 3.8 days. Due to its high radioactivity, it has been less well-studied by chemists, but a few compounds are known. Radon is formed as part of the normal radioactive decay chain of uranium. Uranium has been around since the earth was formed and its most common isotope has a very...more »
Columbia Encyclopedia search results: radon
Results 1 - 10  of 10
  • Periodic Table of the Elements: Radon

    Periodic Table of the Elements: RadonAtomic Number:86Atomic Symbol:RnRadonAtomic Weight:(222)ElectronConfiguration:2 · 8 · 1832 · 18 · 8

  • Rn

    Rn, symbol for the element radon.

  • inert gas

    Inert gas or noble gas, any of the elements in Group 18 of the periodic table. In order of increasing atomic number they are: helium, neon, argon, krypton, xenon, and radon. They are colorless...

  • Redon, Odilon

    Redon, Odilon, 1840–1916, French painter and lithographer. He studied in Paris under Gérôme. Later his friend Fantin-Latour taught him lithography, but he was most influenced by Rodolphe Bresd...

  • argon

    Argon [Gr.,=inert], gaseous chemical element; symbol Ar; at. no. 18; at. wt. 39.948; m.p. -189.2°C; b.p. -185.7°C; density 1.784 grams per liter at STP; valence 0. Argon is a colorless, odorle...

  • fluorine

    Fluorine, gaseous chemical element; symbol F; at. no. 9; at. wt. 18.998403; m.p. -219.6°C; b.p. -188.14°C; density 1.696 grams per liter at STP; valence -1. Fluorine is a yellowish, poisonous,...

  • lung cancer

    Lung cancer, cancer that originates in the tissues of the lungs. Lung cancer is the leading cause of cancer death in the United States in both men and women. Like other cancers, lung cancer oc...

  • radium

    Radium [Lat. radius=ray], radioactive metallic chemical element; symbol Ra; at. no. 88; at. wt. 226.0254; m.p. 700°C; b.p. 1,140°C; sp. gr. about 6.0; valence +2. Radium is a lustrous white ra...

  • thorium

    Thorium [from Thor], radioactive chemical element; symbol Th; at. no. 90; at. wt. 232.0381; m.p. about 1,750°C; b.p. about 4,790°C; sp. gr. 11.7 at 20°C; valence +4.Thorium is a soft, ductile,...

  • Elements (table)

    ElementsElementSymbolAtomic NumberAtomic Weight1Melting Point(Degrees Celsius)Boiling Point(Degrees Celsius)1 Parentheses indicate most stable isotope.actiniumAc89227.02781050.3200....

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