12/7/2023 0 Comments Thorium spontaneous fission![]() ![]() Other uses for thorium include heat-resistant ceramics, aircraft engines, and in light bulbs. Thorium is also used in strengthening magnesium, coating tungsten wire in electrical equipment, controlling the grain size of tungsten in electric lamps, high-temperature crucibles, and glasses including camera and scientific instrument lenses. It has been suggested as a replacement for uranium as nuclear fuel in nuclear reactors, and several thorium reactors have been built. It was also material in high-end optics and scientific instrumentation, used in some broadcast vacuum tubes, and as the light source in gas mantles, but these uses have become marginal. Thorium is still being used as an alloying element in TIG welding electrodes but is slowly being replaced in the field with different compositions. In the second half of the century, thorium was replaced in many uses due to concerns about its radioactivity. Thorium's radioactivity was widely acknowledged during the first decades of the 20th century. Its first applications were developed in the late 19th century. Thorium was discovered in 1828 by the Norwegian amateur mineralogist Morten Thrane Esmark and identified by the Swedish chemist Jöns Jacob Berzelius, who named it after Thor, the Norse god of thunder. Thorium is estimated to be over three times as abundant as uranium in the Earth's crust, and is chiefly refined from monazite sands as a by-product of extracting rare-earth metals. On Earth, thorium and uranium are the only elements with no stable or nearly-stable isotopes that still occur naturally in large quantities as primordial elements. The most stable isotope, 232Th, has a half-life of 14.05 billion years, or about the age of the universe it decays very slowly via alpha decay, starting a decay chain named the thorium series that ends at stable 208 Pb. Thorium is an electropositive actinide whose chemistry is dominated by the +4 oxidation state it is quite reactive and can ignite in air when finely divided.Īll known thorium isotopes are unstable. Thorium is light silver and tarnishes olive gray when it is exposed to air, forming thorium dioxide it is moderately soft and malleable and has a high melting point. Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90.
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