History
Morten Thrane Esmark found a black mineral on Løvøya island, Norway and gave a sample to his father Jens Esmark, a noted mineralogist. The elder Esmark was not able to identify it and sent a sample to Swedish chemist Jöns Jakob Berzelius for examination in 1828. Berzelius determined that it contained a new element, which he named thorium after Thor, the Norse god of thunder. He published his findings in 1829. Berzelius reused the name of a previous element discovery from a mineral from the Falun which later proved to be a yttrium mineral. The metal had no practical uses until Carl Auer von Welsbach invented the gas mantle in 1885.
Thorium was first observed to be radioactive in 1898, independently, by Polish-French physicist Marie Curie and German chemist Gerhard Carl Schmidt. Between 1900 and 1903, Ernest Rutherford and Frederick Soddy showed how thorium decayed at a fixed rate over time into a series of other elements. This observation led to the identification of half-life as one of the outcomes of the alpha particle experiments that led to their disintegration theory of radioactivity.
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.
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.
Thorium-232 is a primordial nuclide, having existed in its current form for over 4.5 billion years, predating the formation of the Earth; it was forged in the cores of dying stars through the r-process and scattered across the galaxy by supernovas. Its radioactive decay produces a significant amount of the Earth's internal heat.
Read more about this topic: Thorium Compounds
Famous quotes containing the word history:
“The steps toward the emancipation of women are first intellectual, then industrial, lastly legal and political. Great strides in the first two of these stages already have been made of millions of women who do not yet perceive that it is surely carrying them towards the last.”
—Ellen Battelle Dietrick, U.S. suffragist. As quoted in History of Woman Suffrage, vol. 4, ch. 13, by Susan B. Anthony and Ida Husted Harper (1902)
“It is the true office of history to represent the events themselves, together with the counsels, and to leave the observations and conclusions thereupon to the liberty and faculty of every man’s judgement.”
—Francis Bacon (1561–1626)
“I assure you that in our next class we will concern ourselves solely with the history of Egypt, and not with the more lurid and non-curricular subject of living mummies.”
—Griffin Jay, and Reginald LeBorg. Prof. Norman (Frank Reicher)