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