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Chemical Elements, scandium to thorium,
Chart 7 of 8

scandium | seaborgium | selenium | silicon | silver | sodium | strontium | sulfur | tantalum | technetium | tellurium | terbium | thallium | thorium

This is the seventh of eight groups of chem elements available in these cross-reference searches.

The Chemical Elements Chart is here.

The Chemical-Elements Table Index is here.

Symbol: Sc
Atomic number: 21
Year discovered: 1879
Discovered by: Lars Fredrik Nilson (1840-1899), a Swedish chemist.

Additional information:
  • Scandium was discovered by Nilson, in 1879, in the minerals “euxenite” and “gadolinite”, which had not yet been found anywhere except in Scandinavia.
  • He and his coworkers were actually looking for rare earth metals.
  • By processing 10 kg of euxenite and other residues of rare-earth minerals, Nilson was able to prepare about 2 g of scandium oxide of high purity.
  • In 1871, Mendeléyev predicted that an element should exist that would resemble boron in its properties.
  • He therefore called it eka-boron, (symbol Eb).
  • Cleve found scandium oxide at about the same time.
  • He noted that the new element was the element eka-boron as predicted by Mendeléyev, in 1871; a second of his predicted elements had thus been discovered.
Name in other languages:
French: scandium
German: Scandium
Italian: scandio
Spanish: escandio

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Symbol: Sg
Atomic number: 106
Year discovered: 1974
Discovered by: Albert Ghiorso (born July 15, 1915) and co-workers at the Lawrence Berkeley Laboratory in California and the Livermore National Laboratory, USA.

Additional information:
  • It is the first time an element has been named for a living person.
  • This element was once named, unnilhexium; Symbol: Unh; which is the Latin equivalent for the number “106”.
  • Transuranium elements such as seaborgium can be created artificially in particle accelerators.
  • Isotopes of seaborgium have short half-lives of less than a second.
  • The first report of element 106 came in 1974 from the Soviet Joint Institute for Nuclear Research and these were followed later by others from Berkeley in California, USA.
  • Experiments at the same American institution confirmed the discovery in 1993.
  • The naming of a chemical element is influenced by national pride, professional rivalry and personal sensitivities; the picking of a single name can provoke as much back-room bickering and bargaining as the selection of the head of the United Nations.
  • The final court of appeals in this process is the International Union of Pure and Applied Chemistry (IUPAC), with member chemists from about 80 countries.
  • Within the Union, factions representing the United States, Germany, Russia and several other nations have bitterly disagreed about names.
  • A particularly sharp disagreement began when the Lawrence Berkeley Laboratory in Berkeley, California, backed by the American Chemical Society, tentatively named element 106, seaborgium, with the chemical symbol Sg.
  • The name honored Glenn T. Seaborg, an American chemist and Nobel laureate, whose team created 10 new elements during and after World War II.
  • In 1940, Seaborg’s research group at Berkeley used an accelerator to make neptunium, the first element heavier than uranium.
  • Before neptunium, the only element existing solely as a laboratory product was technetium, which is No. 43 on the periodic table. It was created in 1937 by the fusion of atomic nuclei.
  • Seaborg’s team went on to create plutonium, the element fueling the atomic bomb that destroyed Nagasaki, and eight other artificial elements.
  • The American Chemical Society believed that international confirmation of the name seaborgium would be mere formality, but instead the international chemists’ union provisionally named Element 106 rutherfordium honoring New Zealand-born physicist Ernest Rutherford.
  • Adding insult to injury, in the view of the Berkeley group, the international union proposed naming element 104, “dubnium”, recognizing achievements in nuclear physics by the Joint Institute for Nuclear Research at Dubna, Russia.
  • The Berkeley scientists and many other American physicists were skeptical of some of the claims made by the Dubna laboratory to having created new elements.
  • After years of debate, the international union in January, 1997, came up with a compromise list that most American chemists deemed acceptable.
  • David F. Eaton, a chemist at DuPont Corporation, who headed the American delegation throughout the bargaining, said in an interview that all of the American laboratories involved in the dispute were satisfied.
  • The union’s members at a meeting in Geneva in August, 1997, confirmed the following as the names of the six new elements: Element 104, rutherfordium (symbol Rf); Element 105, dubnium (symbol Db); Element 106, seaborgium (symbol Sg); Element 107, bohrium (symbol Bh); Element 108, hassium (symbol Hs).
  • Bohrium takes its name from Niels Bohr, a Dane, who was a founder of quantum physics.
  • Hassium is the Latin name for the German province Hessen, the seat of the laboratory where elements 109 and 110 were created, as well as a single atom of element 112 in 1996.
  • Meitnerium is named for the Austrian-born physicist Lise Meitner.
  • Dropped from the union’s previous list of provisional names were “joliotium” for Element 105, for the French physicist Frédéric Joliet-Curie, and “hahnium” for Element 108, honoring the German physicist Otto Hahn.
  • As far as naming element 106, seaborgium, the following will expand on this rare honor to, at the time of the naming, a living recipient.
  • “This is the greatest honor ever bestowed upon me—even better, I think, than winning the Nobel Prize,” said Seaborg, the co-discoverer of plutonium and nine other transuranium elements.
  • “Future students of chemistry, in learning about the periodic table, may have reason to ask why the element was named for me, and thereby learn more about my work.”
  • Seaborgium has a half-life of less than a second. It was first created and identified in 1974 in an experiment conducted at LBL (Lawrence Berkeley Laboratory) by a team of LBL and LNL (Livermore National Laboratory) researchers led by Hulet and LBL physicist Albert Ghiorso.
  • According to criteria proposed by nuclear science researchers in the 1970’s, the naming of a new element is the prerogative of the original discovery team, but proposal of a name should await independent confirmation of the discovery.
  • Seaborgium was finally confirmed in 1993 in an experiment at LBL’s 88-Inch Cyclotron that was designed by Ken Gregorich, a divisional fellow in LBL’s Nuclear Science Division, and carried out by a team including Gregorich and LBL faculty senior scientist Darleane Hofmann, plus postdoctoral fellows and students from LBL and the UC Berkeley Department of Chemistry.
  • Born in 1912 in Ishpeming, Michigan, Seaborg received a Ph.D. in chemistry from UC Berkeley in 1937.
  • He joined the UCB faculty in 1939 and served as chancellor from 1958 to 1961.
  • From 1961 through 1971, Seaborg served as chairman of the Atomic Energy Commission (predecessor of the U.S. Department of Energy) under U.S. Presidents Kennedy, Johnson, and Nixon.
  • He then returned to research at Berkeley, where he continued until 1998 in his search for new elements and isotopes.
  • In addition to his duties at LBL, Seaborg was a University Professor (UC’s highest academic position), and chairman of the Lawrence Hall of Science.
  • Seaborg was perhaps best known for his role in the discovery of plutonium.
  • This took place in 1940, when Seaborg, McMillan, Joseph Kennedy, and Arthur Wahl, using the 60-inch cyclotron built by Ernest Lawrence, bombarded a sample of uranium with deuterons and transmuted it into plutonium.
  • Seaborg and his co-workers used the discovery of plutonium as a stepping stone to the creation of a succession of transuranium elements—americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium, and then seaborgium.
  • Seaborg held more than 40 patents, including the only ones for chemical elements (americium and curium).
  • He was the author of numerous books and more than 500 scientific articles.
  • He has been awarded 50 honorary doctoral degrees and was recognized as a national advocate for science and math education.
  • In the March 1, 1999, issue of The International Herald Tribune, is the announcement: “Glenn Seaborg, 86, U. S. Physicist Who Created Plutonium, Dies”
  • The article goes on to say that Glenn Seaborg, 86, “died Thursday [February 25] at his home in Lafayette, California, following complications of a stroke he suffered in August while exercising on a flight of stairs”.
  • Although he was a chemist by training and occupation, Mr. Seaborg became one of the best known nuclear physicists in history.
  • He led the research that created nine artificial elements, all heavier than uranium. They were plutonium, americium (used today in smoke detectors), curium (used in medicine), berkelium, californium, einsteinium, fermium, mendelevium and nobelium.
  • Two years ago (1997) Element 106, which Mr. Seaborg did not create or discover, was formally named seaborgium in his honor.
  • Until then, no element had been named after a living person.
  • This is the end the synopsis of the Herald Tribune article, dated March 1, 1999.
Name in other languages:
French: seaborgium
German: Seaborgium
Italian: seaborgio
Spanish: seaborgio

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Symbol: Se
Atomic number: 34
Year discovered: 1817
Discovered by: Jöns Jakob Berzelius (1779-1848), a Swedish chemist, who devised chemical symbols, determined atomic weights, contributed to the atomic theory, and discovered several new elements.

Additional information:
  • Jöns Jacob Berzelius reported that tellurium was present in sulfuric acid from a Swedish factory, but in the following year decided that the impurity was not tellurium but another closely related element that he subsequently identified as selenium.
  • Selenium is a chemical element that is closely allied in physical and chemical properties with sulfur.
  • In 1873, Willoughby Smith discovered that crystalline selenium developed a tremendous increase in electrical conductivity when exposed to light, regaining its resistance immediately when the light was shut off.
  • This property eventually was applied in motion-picture sound tracks, television, the telegraphic transmission of photographs, and many other devices depending on light-sensitive materials.
  • Some species of plants are not only tolerant of selenium, but actually require selenium for growth and development.
  • When used as food for animals or humans, the plants are toxic, causing either chronic or fatal poisoning.
  • Selenium poisoning in horses is accompanied by loss of hair from tail and mane and by abnormal hoof growth; extreme cases produce blind staggers or even death.
  • In humans, selenium may concentrate in the lungs, liver, kidney, or spleen.
  • Occupational dermatitis is a mild form of poisoning.
  • Few cases of death have been reported.
  • Recent studies indicate arsenic as a possible inhibitor for selenium poisoning.
  • It is known that soils which are leached by abundant ground water lose some selenium and that plants grown in areas of plentiful rainfall contain less selenium, even though the soil contains the element.
  • The Colorado river, for example, carries away selenium from certain irrigated areas in the western United States.
  • Bottom deposits and growths in the Gulf of California and the Gulf of Mexico contain notable amounts of selenium.
Name in other languages:

French: sélénium

German: Selen
Italian: selenio
Spanish: selenio

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Symbol: Si
Atomic number: 14
Year discovered: 1824
Discovered by: Baron Jöns Jakob Berzelius (1779-1848), a Swedish chemist, who devised chemical symbols, determined atomic weights, contributed to the atomic theory, and discovered several new elements.

Additional information:
  • Silicon is found in measurable amounts in practically every rock, in all natural waters, in sand, in glass, in the atmosphere (as siliceous dust), in many plants and in the skeletons, tissues, and in the body fluids of some animals.
  • It holds on to other atoms so tightly that it is not easy to isolate.
  • It is never found in a free state, but always in combination either with oxygen as silica, or with oxygen and aluminum, magnesium, calcium, sodium, potassium, iron, and other elements in the numerous silicate materials which comprise rocks, soils, and clays.
Name in other languages:
French: silicium
German: Silicium
Italian: silicio
Spanish: silicio

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Symbol: Ag
Atomic number: 47
Year discovered: Prehistoric; known since ancient times.
Discovered by: Unknown

Additional information:
  • Together with gold, iridium, palladium, and platinum; silver is considered one of the so-called precious metals.
  • Because of its comparative scarcity, brilliant white color, malleability, and resistance to atmospheric oxidation, it has long been used in the manufacture of articles of value such as coins, ornaments, and jewelry.
  • In addition to uses as jewelry, etc., silver has a number of applications, most of which depend on its high thermal or electrical conductivity and corrosion resistance.
  • When it has been hardened by elements such as copper or gold, it is used in electrical contacts.
  • Early Roman records show that before the use of the term “argentum”, the word “Luna” and a crescent moon symbol were used for silver.
  • The actual use of silver dates far back into antiquity; however, it is believed that gold and copper were the first metals to be worked by man.
  • By 800 B.C. it is probable that both gold and silver were used as money in all countries between the Indus and the Nile.
  • The Romans probably advanced the art and science of metallurgy of silver further than any other people up to their time.
  • From about 1850, 65 per cent or more of the world production of silver was derived as a by-product in the smelting and refining of copper, lead, and zinc ores.
Name in other languages:
French: argent
German: Silber
Italian: argento
Spanish: plata

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Symbol: Na
Atomic number: 11
Year discovered: 1807
Discovered by: Sir Humphry Davy (1778-1829), an English chemist.

Additional information:
  • Until the 18th century no distinction was made between potassium and sodium.
  • This was because early chemists did not recognize that “vegetable alkali” (potassium carbonate, coming from deposits in the earth) and “mineral alkali” (sodium carbonate, derived from wood ashes) are distinct from each other.
  • Eventually a distinction was made. Sodium was isolated in 1807 by Sir Humphry Davy, who obtained it through the electrolysis of very dry molten sodium hydroxide.
  • It was known that an electric current would break up water molecules into hydrogen and oxygen when more customary chemical methods failed.
  • Metallic sodium is a soft silvery white material that tarnishes rapidly in air because of the formation of a film of the oxide.
  • Sodium is very widely distributed in the form of its compounds, of which ordinary salt, or sodium chloride, is the most familiar.
Name in other languages:
French: sodium
German: Natrium
Italian: sodio
Spanish: sodio

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Symbol: Sr
Atomic number: 38
Year discovered: First in 1790, by Adair Crawford of Scotland; then again in 1808, by Sir Humphry Davy, an English chemist.
Discovered by: Adair Crawford, of Scotland, in 1790 and Sir Humphry Davy (1778-1829), an English chemist, in 1808.

Additional information:
  • Adair Crawford in 1790 recognized a new mineral (strontianite) in samples of witherite (a mineral consisting of barium carbonate) at Strontian in Argyll, Scotland.
  • It was some time before it was recognized that strontianite contained a new element.
  • Strontianite is now known to consist of strontium carbonate.
  • The element itself was not isolated for a number of years after this when strontium metal was isolated by Davy by electrolysis of a mixture containing strontium chloride and mercuric oxide in 1808.
  • It is distributed in small quantities in many different rocks and soils.
  • Some is present in bones, in which it replaces small amounts of calcium.
  • Compounds of strontium are not as extensively used as those of calcium or barium.
Name in other languages:
French: strontium
German: Strontium
Italian: stronzio
Spanish: estroncio

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Symbol: S
Atomic number: 16
Year discovered: Prehistoric; known since ancient times.
Discovered by: Unknown

Additional information:
  • Sulfur got its name from the Latin word for brimstone (burning stone), and ignited sulfur is mentioned in the earlier records of many countries as having been used for religious ceremonies, for purifying (fumigating) buildings, and for bleaching cloth.
  • The Romans also used it in medicine and in warfare.
  • During the Middle Ages the alchemists regarded sulfur as the principle of combustibility.
  • It was first classified as an element by Lavoisier, in 1777, but many of his contemporaries considered it a compound of hydrogen and oxygen.
  • Joseph Gay-Lussac and Louis Thénard finally proved it was an element in 1809.
Name in other languages:
French: soufre
German: Schwefel
Italian: solfo
Spanish: azufre

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Symbol: Ta
Atomic number: 73
Year discovered: 1802
Discovered by: Anders Gustav Ekeberg (1767-1813), Swedish chemist.

Additional information:
  • Niobium was discovered, in 1802, by Anders Gustaf Ekenberg (1767-1813), but many chemists thought niobium and tantalum were identical elements until Rose, in 1844, and Marignac, in 1866, indicated and showed that niobic and tantalic acids were not the same.
  • In the previous year, Charles Hachett (1765-1847), a British chemist, also had discovered a new element that he named columbium.
  • Because of the similarity of the compounds of the two elements, they were regarded as being the same until, in 1844, Heinrich Rose, a German chemist, discovered both tantalum and a new element that he named niobium (for Niobe, daughter of Tantalus) in the mineral columbite.
  • Later Rose realized that niobium and colombium were the same element.
  • In 1866, niobium and tantlum compounds were actually separated by Swiss chemist J. C. G. de Marignac, thus permitting studies of the compounds of each element.
  • Although some impure tantalum was produced by several early investigators, it was not until 1903 that the first ductile tantalum was produced by W. von Bolton in Germany.
  • This ductile tantalum was used for incandescent lamp filaments until tungsten began to replace it in 1909.
  • The first production of tantalum in the United States started in 1922.
  • About this time C. W. Balke discovered that intentionally oxidized tantalum made an excellent rectifier of alternating current and its use in radio receiving sets and capacitors was established.
  • Since then the use of tantalum in the electronics and chemical industries has grown steadily.
  • The most important uses for tantalum are in electrolytic capacitors and corrosion-resistant chemical equipment.
Name in other languages:
French: tantale
German: Tantal
Italian: tantalio
Spanish: tántalo

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Symbol: Tc
Atomic number: 43
Year discovered: 1937
Discovered by: Emilio Gino Segré (1905-1989), an Italian physicist, and Carlo Perrier of Italy.

Additional information:
  • Element 43 (technetium) was predicted on the basis of the periodic table by Mendeléyev.
  • He suggested that it should be very similar to manganese and gave it the name eka-manganese.
  • Technetium was erroneously reported as having been discovered in 1925, at which time it was named masurium.
  • The element was actually discovered by C. Perrier and Emilio Gino Segrè in Italy in 1937.
  • It was found in a sample of molybdenum bombarded by deuterons.
  • Technetium was the first element to be produced artificially and all its isotopes are radioactive.
  • It is named after the Greek word technetos, meaning “artificial”.
  • *** In the February, 2000, issue of Scientific American, page 9, there is an article titled, “An Elemental Mystery” (Who really discovered element 43?) by Alden M. Hayashi in which he states that In 1925 German chemist Ida Tacke and her colleagues (Walter Noddack [who would become her husband] and Otto Berg) made a stunning announcement:
  • Using x-ray spectroscopy, they had reportedly discovered element 43, which they named masurium.
  • Ernest O. Lawrence, the Nobel Prize-winning physicist, called the masurium investigators “apparently deluded.”
  • As stated earlier, credit for the discovery of element 43 went to Carlo Perrier and Emilio Segré in 1937, which they named technetium.
  • The Noddack team fired a beam of electrons at different materials, inducing them to emit x-rays.
  • With this technique, Noddack and her colleagues analyzed columbite ores—a black mineral consisting of niobium—and obtained faint x-ray spectral lines that appeared to correspond to the radioactive element 43.
  • “I thought it was impossible that they had discovered technetium. But after looking more closely into it, I decided that you couldn’t automatically throw out their claim,” says Albert Ghiorso of Lawrence Berkeley National Laboratory.
  • Ghiorso, by the way, worked with Glenn T. Seaborg to discover several of the transuranic elements that had eluded Enrico Fermi who thought he had synthesized transuranic elements and even won a Nobel Prize for his supposed discovery of transuranic elements.
  • So what we have here is a strong possibility that German chemist Ida Tacke, with Walter Noddack and Otto Berg, actually discovered element 43 in 1925, twelve years before the claim made by Carlo Perrier and Emilio Segré.
Name in other languages:
French: technétium
German: Technetium
Italian: tecneto
Spanish: tecnecio

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Symbol: Te
Atomic number: 52
Year discovered: 1782
Discovered by: Franz Joseph Müller von Reichstein (1740-1825), an Austrian mineralogist.

Additional information:
  • Tellurium was discovered in gold ores by Franz Joseph Müller von Reichenstein, the chief inspector of mines in Trannsylvania, in 1782.
  • While examining the Transylvanian gold minerals, Müller suspected the presence of a new element and called it “metallum problematicum” or “aurum paradoxum”.
  • Feeling inadequate to the task of settling the matter, he sent the substance to a German chemist, Martin Heinrich Klaproth, for further research.
  • In 1784, Klaproth confirmed that the material was a new element, named it tellurium (from a Latin word for "earth"), and was careful to give full credit for the discovery to Müller.
  • In 1798, Klaproth extracted tellurium from white gold ore, and named it, and established its identity as differing from antimony, with which it had been confused.
  • Although comparatively large supplies of tellurium are available, there are not any significant uses that create a big demand for it.
Name in other languages:
French: atellure
German: Tellur
Italian: tellurio
Spanish: teluro

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Symbol: Tb
Atomic number: 65
Year discovered: 1843
Discovered by: Carl Gustav Mosander (1797-1858), a Swedish scientist.

Additional information:
  • Terbium was discovered by Carl Gustav Mosander in 1843.
  • He detected it as an impurity in yttria which is yttrium oxide.
  • Its existence was not confirmed for at least 30 years and pure compounds were not prepared until 1905.
Name in other languages:
French: terbium
German: Terbium
Italian: terbio
Spanish: terbio

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Symbol: Tl
Atomic number: 81
Year discovered: 1861
Discovered by: Sir William Crookes (1832-1919), a British physicist.

Additional information:
  • Thallium was discovered spectroscopically, in 1861, by Crookes as he examined the flue dust produced in the roasting of seleniferous pyrites.
  • The element was named after the green spectral line, that identified it and was foreign to all of the then known spectra and so he concluded that the mineral contained a new element, which he named thallium, from Greek for “a green twig”.
  • Crookes presumed that his thallium was something of the order of sulfur, selenium, or tellurium; but the French chemist Claude-Auguste Lamy, who anticipated him in isolating the new element (1862), found it to be a metal.
  • They had expected to isolate tellurium after removing selenium from the by-products of a commercial sulfuric acid factory, but instead found the new element thallium.
  • The pure metal is not commercially important, but thallium salts have a number of laboratory and industrial uses.
  • Thallium forms two series of salts: thallous, in which the metal is univalent; and thallic, in which it is trivalent.
  • All thallium salts are poisonous, producing symptoms somewhat resembling those of lead poisoning.
Name in other languages:
French: thallium
German: Thallium
Italian: tallio
Spanish: talio

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Symbol: Th
Atomic number: 90
Year discovered: 1828
Discovered by: Baron Jöns Jakob Berzelius (1779-1848), a Swedish chemist, who devised chemical symbols, determined atomic weights, contributed to the atomic theory, and discovered several new elements.

Additional information:
  • Thorium was discovered by Berzelius, in 1828, in a mineral given to him by the Reverend Has Morten Thrane Esmark.
  • In electronic devices thorium oxide is widely used as a source of primary electron emission.
  • The advent of atomic energy, jet turbines, and rockets brought an unusual demand for new metals and alloys.
  • Important alloys containing thorium were developed for improving the high-temperature strength of metals, in particular the magnesium base alloys.
  • Thorium powder is relatively stable in air, but spontaneous combustion has occurred and the storage of large quantities is hazardous.
  • In 1898, Marie Curie showed that thorium also produced radiations, and she coined the term radioactivity for the phenomenon, so that it can be said that both uranium and thorium are radioactive.
Name in other languages:
French: thorium
German: Thorium
Italian: torio
Spanish: torio