 Discovery Information
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| Who: Jöns Berzelius |
| When: 1828 |
| Where: Sweden |
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| Name Origin
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| From the Scandinavian god Thor. |
| "Thorium" in different languages. |
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| Sources
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| Found in various minerals like monazite and thorite ((Th,U)SiO4). Thorium is found in small amounts in most rocks and soils (about 6ppm), where it is three times more abundant than uranium and about as common as lead.
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| Primary producers are the USA, Brazil, India, Sri Lanka, Madagascar, Russia and Australia. Annual production is around 31 thousand tons.
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| Abundance
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| Universe: 0.0004 ppm (by weight) |
| Sun: 0.0003 ppm (by weight) |
| Carbonaceous meteorite: 0.04 ppm |
| Earth's Crust: 12 ppm |
| Seawater: 9.2 ppm |
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| Uses
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| Used in making strong alloys, ultraviolet photoelectric cells, mantles in portable gas lights and for coating tungsten wire in electronic equipment. Bombarded with neutrons make uranium-233, a nuclear fuel.
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| Thorium dioxide (ThO2) is used in producing high-temperature laboratory crucibles. When added to glass it helps create glasses of a high refractive
index and with low dispersion. Consequently, they find application in high-quality lenses for cameras and scientific instruments.
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| History
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| M. T. Esmark found a black mineral on Lovoy Island, Norway and gave a sample to Professor Jens Esmark, a noted mineralogist who was not able to identify it so he sent a sample to the
Swedish chemist Jöns Jakob Berzelius for examination in 1828. Berzelius analysed it and named it after Thor, the Norse god of thunder. The metal had virtually no uses until the invention of the
gas mantle in 1885.
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| The crystal bar process (or Iodide process) was discovered by Anton Eduard van Arkel and Jan Hendrik de Boer in 1925 to produce
high-purity metallic thorium.
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| The name ionium was given early in the study of radioactive elements to the 230Th isotope produced in the decay chain of 238U before it was realized that ionium and thorium were chemically identical. The symbol Io was used for this supposed element.
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| Notes
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| Thorium dioxide (ThO2), also called thoria, has one of the highest melting points of all oxides (3300°C).
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