Discovery of the chemical elements

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The discovery of the chemical elements, in chronological order. These are listed generally in the order in which they were first isolated as the pure element, rather than as a compound (it was known that 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

Phosphorus 1670 Hennig Brandt, later described by Robert Boyle
Cobalt     1732

Platinum had been noticed in South American gold ore since the 16th century, a number of chemists worked on Platinum in the 18th century:

Platinum    ca. 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   M.H. Klaproth
Zirconium
Strontium  1793   M.H. Klaproth
Titanium   1797   M.H. 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    M.H. Klaproth; Jöns Jacob Berzelius and Hisinger 
Rhodium
Palladium
Osmium
Iridium
Magnesium

At this point, Humphrey 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

Potassium   1807   Humphrey Davy
Calcium
Sodium      1807   Humphrey Davy                    
Barium      1808   Humphrey Davy
Iodine
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   Jöns Jacob Berzelius
Silicon
Aluminium   1825   Hans Christian Ørsted
Bromine     1826    A.J. Balard
Thorium            Jöns Jacob Berzelius
Beryllium   1828   Friedrich Wöhler

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 `Didymium' (didymium was not actually one element, and was resolved into two in 1885)

Lanthanum   1839-41 Mosander
Terbium
Erbium
Ruthenium

Spectroscopic discoveries

A number of elements were first identified by their spectroscopic emission lines: Cesium and Rubidium were discovered by Bunsen and Kirchhoff analysing the spectrum of alkali salts. The unknown element with blue emission lines was named caesium (later cesium); 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:

Cesium      1860   Bunsen 
Rubidium    1860   Bunsen
Thallium    1861   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

Helium      1868           


Boron       1868   J.L. 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     1871     de Boisbaudran 
Ytterbium
Thulium     1879   P.T. Cleve
Scandium    1879   Nilson 
Holmium
Samarium
Gadolinium

The 'didymium' isolated by Mosander in 1839 was shown to actually be two separate elements, praseodymium and neodymium:

Praseodymium 1885  Carl Auer von Welsbach
Neodymium    1885  Carl Auer von Welsbach
Dysprosium
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
Europium

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
Krypton      1898   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              Pierre and Marie Curie
Polonium            Pierre and Marie Curie
Actinium     1899   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                Pierre and Marie Curie
Lutetium
Protactinium
Hafnium
Rhenium

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.

Technetium                                   Synthetic                    
Francium                                  

All subsequent elements after this are synthetic elements:

Astatine       1940     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 at Berkeley
Plutonium      1941     Glenn T. Seaborg, Arthur C. Wahl, Joseph W. Kennedy Elilijo Segre
Curium                    
Americium                      
Promethium           
Berkelium      1949     Stanley. Albert Ghiorso, Kennerth Stret Jnr, Glenn T. Seaborg
Californium    1950     Stanley. Albert Ghiorso, Kennerth Stret Jnr, Glenn T. Seaborg
Einsteinium         
Fermium                       
Mendelevium    1955     Glenn T. Seaborg, Evans G. Valens
Nobelium       1958
Lawrencium     1961      
Rutherfordium  1964          
Dubnium              
Seaborgium
Bohrium
Hassium
Meitnerium
              

see also periodic table


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