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.
Platinum had been noticed in South American gold ore since the
16th century. A number of chemists worked on platinum in the
18th century:
Priestley's work on atmospheric gases resulted\nin his preparation of oxygen. As he was a believer in
phlogiston, he didn't realise that he had prepared a new\nelement, and thought that he had managed to prepare air free from\nphlogiston ("de-phlogisticated air"). However, he
was the\nfirst to isolate oxygen, even if he didn't realise what he had:
The recent discovery of the new planet
Uranus by
William Herschel had caused a stir, so the newly discovered metallic\nelement was christened uranium in its honour.
The next element was discovered just after the discovery of a new\nclass of astronomical objects: the new element was named after the\nnewly discovered
asteroid,
Ceres. The element was\ndiscovered nearly simultaneously in two laboratories, though it was\nlater shown that Berzelius and Hisinger's cerium was actually a\nmixture of cerium, lanthanum and didymium.
At this point, Sir
Humphry Davy pioneered the use of
electricity\nfrom the
Voltaic pile to decompose the salts of alkali metals,\nand so a number of thse metals were first prepared as the pure\nelement: the beginning of the field of
electrochemistry.
The next element discovered when Mosander showed that the cerium\nisolated in
1803 by Berzelius was actually a mixture of cerium,\nlanthanum and so-called didymium (which was not actually one element,\nand was resolved into two in
1885).
Spectroscopic discoveries
A number of elements were first identified by their spectroscopic\nemission lines: caesium and rubidium were discovered by Bunsen and
Kirchhoff\nanalysing the spectrum of alkali salts. The unknown element with\nblue emission lines was named caesium; in purifying\nthe salts of this new element, another element was discovered with\na red emission line; this was called rubidium.. They were shortly\nafterwards prepared as the pure salts by Bunsen. The bright green\nline of thallium caused it to be named from the Greek
thallos,\nmeaning a green shoot, and the indigo-blue line from certain\nspecimens of zinc-blende gave the name indium to the new element so\ndiscovered:
Another spectroscopic discovery, helium was found by astronomers as\nan emission line in the spectrum of the sun, hence its name from\nthe Greek
helios meaning sun. It was at first thought to be an\nunknown metallic element, and so the name was given the ending -ium\nto signify a metal. By the time it had been found on Earth and\ndiscovered to be the lightest of the noble gases, the name was\nfixed; by analogy with the other noble gases, the name should have\nended in -on.
The Periodic table and the prediction of new elements
In 1871,
Mendeleev predicted,\nfrom the gaps in his newly-devised
periodic table, that there\nshould be three as yet undiscovered elements, which he named\neka-boron, eka-aluminium, and eka-silicon. With Mendeleev's\nprediction of their existence and approximate chemical properties,\nthe missing elements were found by French, Scandinavian, and German\nchemists, and named for their countries of discovery, as gallium,\nscandium, and germanium:
The 'didymium' isolated by Mosander in
1839 was shown to\nactually be two separate elements, praseodymium and neodymium:
Refrigeration technology advanced considerably during the
19th century, to the point where it was possible to liquefy atmospheric\ngases. A curious observation was made: Nitrogen prepared by\nchemical means from its compounds had a slightly lower molecular\nweight than nitrogen prepared by liquefaction from air. This was\nattributed as being due to the presence of a previously unsuspected\ngas, christened argon. This gas was the first representative found\nof a previously unsuspected new group in the periodic table, first\nknown as the inert gases, now more commonly known as the
noble gases.
Once liquid argon could be prepared in quantity from air, small\namounts of a further three noble gases could be separated from it\nby differences in boiling point. These new elements were named from\nthe Greek words for, respectively, 'new', 'hidden', and 'foreign'.
With the discovery of
radioactivity, we have the classic work\nby the Curies that isolated a number of previously unknown\nelements:
Another of the noble gases, radon had avoided discovery because its\nshort radioactive half-life had meant it was present in air in\nvanishingly tiny quantities. Once radium was available in\nmacroscopic quantities, the production of this radioactive noble\ngas was readily detected as a product of radium's radioactive\ndecay.
At this point, all the stable elements existing on earth had been\ndiscovered, and most of the periodic table had been filled. A few\ngaps remained amongst the higher mass elements, but there remained\na troublesome gap at element number 43, just below manganese in the\ntable. The gaps were filled by the synthetic elements.\nWalter Noddack and Ida Tacke (later Ida Noddack) also believed to have found Technetium, which they called Masurium (after Masurien, an area in Germany).\nThey were later proved wrong.
The synthetic elements
The so-called "synthetic" elements are unstable, with \n
half-lives so "short" relative to the age of the earth that any\natoms of that element that may have been present when the earth\nformed have long since completely decayed away. Hence they are\nonly known on earth as the product of
nuclear reactors, \n
particle accelerators, or in the byproducts from nuclear explosions. The discovery of technetium finally\nfilled in a puzzling gap in the
periodic table, and the\ndiscovery that there were no stable isotopes of technetium\nexplained its absence on earth: its
4.2 million years\nhalf-life meant that none remained from the time of formation of\nthe earth.
All elements after this are synthetic:
\n\n| Astatine | \n1940 | \nDale R. Corson, K.R.Mackenzie, Emilio Segre' | \n
\n
The next two elements were the first of the
transuranic (beyond uranium) elements and were named\nafter the planets beyond
Uranus,
Neptune and
Pluto:
\n\n| Neptunium | \n1940 | \nE.M. McMillan & Philip H. Abelson,\nUniversity of California, Berkeley | \n
\n| Plutonium | \n1941 | \nGlenn T. Seaborg, Arthur C. Wahl, Joseph W. Kennedy Emilio\nSegré | \n
\n| Curium | \n1944 | \nGlenn T. Seaborg | \n
\n| Americium | \n1945 | \nGlenn T. Seaborg | \n
\n| Promethium | \n1945 | \nJ.A. Marinsky | \n
\n| Berkelium | \n1949 | \nAlbert Ghiorso, Glenn T. Seaborg, Stanley G. Thompson, Kenneth Street Jr | \n
\n| Californium | \n1950 | \nAlbert Ghiorso, Glenn T. Seaborg, Stanley G. Thompson, Kenneth Street Jr | \n
\n| Einsteinium | \n1952 | \nArgonne Laboratory, Los Alamos Laboratory, and University of California | \n
\n| Fermium | \n1953 | \nArgonne Laboratory, Los Alamos Laboratory, and University of California | \n
\n| Mendelevium | \n1955 | \nGlenn T. Seaborg, Evans G. Valens | \n
\n| Nobelium | \n1958 | \nAlbert Ghiorso, Glenn T. Seaborg, John R. Walton and Torbørn Sikkeland | \n
\n| Lawrencium | \n1961 | \n Albert Ghiorso, Torbjorn Sikkeland, Almon Larsh and Robert M. Latimer | \n
\n| Rutherfordium | \n1964 | \nJoint Nuclear Research Institute at Dubna, U.S.S.R. | \n
\n| Dubnium | \n1970 | \nAlbert Ghiorso | \n
\n| Seaborgium | \n1974 | \n Joint Nuclear Research Institute and University of California, Berkeley | \n
\n| Bohrium | \n1976 | \nY. Oganessian et al, Dubna and confirmed at GSI (1982) | \n
\n| Meitnerium | \n1982 | \nPeter Armbruster and Gottfried Münzenberg, GSI | \n
\n| Hassium | \n1984 | \n Peter Armbruster and Gottfried Münzenberg | \n
\n| Darmstadtium | \n1994 | \nS. Hofmann, V. Ninov et al, GSI | \n
\n\n| Unununium | \n1994 | \nS. Hofmann, V. Ninov et al, GSI | \n
\n\n| Ununbium | \n1996 | \nS. Hofmann, V. Ninov et al, GSI | \n
\n| Ununquadium | \n1999 | \nJoint Nuclear Research Institute at Dubna | \n
\n| Ununtrium | \n2004 | \n Joint Nuclear Research Institute at Dubna and Lawrence Livermore National Laboratory | \n
\n| Ununpentium | \n2004 | \n Joint Nuclear Research Institute at Dubna and Lawrence Livermore National Laboratory | \n
\n
See also
\n* Periodic table\n*
Elements song\n*
Timeline of chemical element discovery
Category:History of science\nCategory:Chemical elements
