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Discoveries of the chemical elements

The story of the discoveries of the chemical elements is presented here in chronological order. The elements are listed generally in the order in which they were first isolated as the pure element, rather than as a compound (some such as boron were known to be elements decades before they could be isolated from their compounds). The first few predate any written record. Carbon from antiquity Gold from antiquity Silver from antiquity Copper from antiquity Sulphur from antiquity Tin from antiquity Lead from antiquity Mercury from antiquity Iron from antiquity Arsenic Antimony - Bismuth 15th century? May have been described in writings attributed to Basil Valentinus Phosphorus1669 Hening Brand, later described by Robert Boyle Cobalt 1732 George Brandt Platinum had been noticed in South American gold ore since the 16th century. A number of chemists worked on platinum in the 18th century: Platinumca. 1750s Zinc Nickel Hydrogen Fluorine Nitrogen Priestley's work on atmospheric gases resulted in his preparation of oxygen. As he was a believer in phlogiston, he didn't realise that he had prepared a new element, and thought that he had managed to prepare air free from phlogiston ("de-phlogisticated air"). However, he was the first to isolate oxygen, even if he didn't realise what he had: Oxygen 1771 Joseph Priestley Chlorine 1774 Karl Wilhelm Scheele Manganese 1780? Hjelm Molybdenum Tellurium 1782 Mueller von Reichenstein Tungsten 1783 The recent discovery of the new planet Uranus by William Herschel had caused a stir, so the newly discovered metallic element was christened uranium in its honour. Uranium 1789 Martin Heinrich Klaproth Zirconium Strontium1793 Martin Heinrich Klaproth Titanium 1797 Martin Heinrich Klaproth Yttrium Chromium Columbium Tantalum The next element was discovered just after the discovery of a new class of astronomical objects: the new element was named after the newly discovered asteroid, Ceres. The element was discovered nearly simultaneously in two laboratories, though it was later shown that Berzelius and Hisinger's cerium was actually a mixture of cerium, lanthanum and didymium. Cerium 1803 Martin Heinrich Klaproth; Jšns Jacob Berzelius and Hisinger Rhodium Palladium Osmium Iridium Magnesium At this point, Sir Humphry Davy pioneered the use of electricity from the Voltaic pile to decompose the salts of alkali metals, and so a number of thse metals were first prepared as the pure element: the beginning of the field of electrochemistry. Potassium1807 Humphry Davy Calcium 1808 Humphry Davy Sodium 1807 Humphry Davy Barium 1808 Humphry Davy Iodine 1811 Bernard Courtois Lithium 1817 Arfvedson (metal prepared by Bunsen using electrolysis in 1855) [This is unclear] Cadmium 1817 Friedrich Strohmeyer Independently discovered by K.S.L Hermann Selenium 1817 Jšns Jacob Berzelius Silicon 1823 Jšns Jacob Berzelius Aluminium1825 Hans Christian Żrsted Bromine 1826 Antoine Jerome Balard Thorium 1828 Jšns Jacob Berzelius Beryllium1828 Friedrich Wšhler Independently discovered by A.A.B. Bussy Vanadium The next element discovered when Mosander showed that the cerium isolated in 1803 by Berzelius was actually a mixture of cerium, lanthanum and so-called didymium (which was not actually one element, and was resolved into two in 1885). Lanthanum1839-41 Carl Mosander Terbium 1843 Carl Mosander Erbium 1843 Carl Mosander Ruthenium1844 Karl Klaus Spectroscopic discoveries A number of elements were first identified by their spectroscopic emission lines: caesium and rubidium were discovered by Bunsen and Kirchhoff analysing the spectrum of alkali salts. The unknown element with blue emission lines was named caesium; in purifying the salts of this new element, another element was discovered with a red emission line; this was called rubidium.. They were shortly afterwards prepared as the pure salts by Bunsen. The bright green line of thallium caused it to be named from the Greek thallos, meaning a green shoot, and the indigo-blue line from certain specimens of zinc-blende gave the name indium to the new element so discovered: Caesium 1860 Bunsen Rubidium1860 Bunsen Thallium1861 Sir William Crookes Indium 1863 Reich and Richter Another spectroscopic discovery, helium was found by astronomers as an emission line in the spectrum of the sun, hence its name from the Greek helios meaning sun. It was at first thought to be an unknown metallic element, and so the name was given the ending -ium to signify a metal. By the time it had been found on Earth and discovered to be the lightest of the noble gases, the name was fixed; by analogy with the other noble gases, the name should have ended in -on. Helium1868 Boron 1868 Joseph Louis Gay-Lussac & L.J. Thenard The Periodic table and the prediction of new elements In 1871, Mendeleev predicted, from the gaps in his newly-devised periodic table, that there should be three as yet undiscovered elements, which he named eka-boron, eka-aluminium, and eka-silicon. With Mendeleev's prediction of their existence and approximate chemical properties, the missing elements were found by French, Scandinavian, and German chemists, and named for their countries of discovery, as gallium, scandium, and germanium: Gallium 1875 de Boisbaudran Ytterbium 1878 Jean de Marignac Thulium 1879 P.T. Cleve Scandium 1879 Nilson Holmium 1879 J.L. Soret Samarium 1879 Paul Emile Lecoq de Boisbaudran Gadolinium1880 Jean de Marignac The 'didymium' isolated by Mosander in 1839 was shown to actually be two separate elements, praseodymium and neodymium: Praseodymium1885 Carl Auer von Welsbach Neodymium 1885 Carl Auer von Welsbach Dysprosium 1886 Paul Emile Lecoq de Boisbaudran Germanium 1886 Winkler Refrigeration technology advanced considerably during the 19th century, to the point where it was possible to liquefy atmospheric gases. A curious observation was made: Nitrogen prepared by chemical means from its compounds had a slightly lower molecular weight than nitrogen prepared by liquefaction from air. This was attributed as being due to the presence of a previously unsuspected gas, christened argon. This gas was the first representative found of a previously unsuspected new group in the periodic table, first known as the inert gases, now more commonly known as the noble gases. Argon 1894 Rayleigh & Sir William Ramsay Europium1901 Eugene Demarcay Once liquid argon could be prepared in quantity from air, small amounts of a further three noble gases could be separated from it by differences in boiling point. These new elements were named from the Greek words for, respectively, 'new', 'hidden', and 'foreign'. Neon 1898 Sir William Ramsay Krypton1898 Sir William Ramsay Xenon 1898 Sir William Ramsay With the discovery of radioactivity, we have the classic work by the Curies that isolated a number of previously unknown elements: Radium 1898 Pierre Curie and Marie Curie Polonium1898 Pierre Curie and Marie Curie Actinium1899 A Debierne Another of the noble gases, radon had avoided discovery because its short radioactive half-life had meant it was present in air in vanishingly tiny quantities. Once radium was available in macroscopic quantities, the production of this radioactive noble gas was readily detected as a product of radium's radioactive decay. Radon 1898 Fredrich Ernst Dorn who called it nitron Lutetium 1907 Georges Urbain Protactinium1917 Kasimir Fajans, O. Gšhring, Fredrich Soddy, John Cranston, Lise Meitner and Otto Hahn Hafnium 1923 Dirk Coster Rhenium 1925 Walter Noddack At this point, all the stable elements existing on earth had been discovered, and most of the periodic table had been filled. A few gaps remained amongst the higher mass elements, but there remained a troublesome gap at element number 43, just below manganese in the table. The gaps were filled by the synthetic elements. The synthetic elements The elements labelled as "synthetic" are unstable, with a half-life so "short" relative to the age of the earth that any atoms of that element that may have been present when the earth formed, have long since completely decayed away. Hence they are only known on earth as the product of nuclear reactors or particle accelerators. The discovery of technetium finally filled in a puzzling gap in the periodic table, and the discovery that there were no stable isotopes of technetium explained its absence on earth: its 4.2 million years half-life meant that none remained from the time of formation of the earth. Technetium1937 Carlo Perrier (Synthetic) Francium 1939 Marguerite Derey All elements after this are synthetic: Astatine1940 Dale R. Corson, K.R.Mackenzie, Emilio Segre' The next two elements were the first of the transuranic (beyond uranium) elements and were named after the planets beyond Uranus, Neptune and Pluto: Neptunium 1940 E.M. McMillan & Philip H. Abelson, University of California, Berkeley Plutonium 1941 Glenn T. Seaborg, Arthur C. Wahl, Joseph W. Kennedy Emilio SegrŽ Curium 1944 Glenn T. Seaborg Americium 1945 Glenn T. Seaborg Promethium 1945 J.A. Marinsky Berkelium 1949 Stanley. Albert Ghiorso, Kennerth Stret Jr., Glenn T. Seaborg Californium 1950 Stanley. Albert Ghiorso, Kennerth Stret Jr., Glenn T. Seaborg Einsteinium 1952 Argonne Laboratory, Los Alamos Laboratory, and University of California Fermium 1953 Argonne Laboratory, Los Alamos Laboratory, and University of California Mendelevium 1955 Glenn T. Seaborg, Evans G. Valens Nobelium 1958 Lawrencium 1961 Rutherfordium1964 Dubnium 1970 Albert Ghiorso Seaborgium 1974 Bohrium 1976 Y. Oganessian et al, Dubna and confirmed at GSI (1982) Hassium 1984 Meitnerium 1982 Peter Armbruster and Gottfried Mźnzenberg, GSI Darmstadtium 1994 S. Hofmann, V. Ninov et al, GSI Unununium 1994 S. Hofmann, V. Ninov et al, GSI Ununbium 1996 S. Hofmann, V. Ninov et al, GSI Ununquadium 1999
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