Chemical Elements, cadmium to einsteinium,
Chart 2 of 8

cadmium | calcium | californium | carbon | cerium | cesium | chlorine | chromium | cobalt | copper | curium | dubnium | dysprosium | einsteinium

This is the second of eight groups of chem elements available in this cross-reference searches.

The Chemical Elements Chart is here.

The Chemical-Elements Table Index is here.

Symbol: Cd
Atomic number: 48
Year discovered: 1817
Discovered by: Friedrich Strohmeyer (1776-1835), a German chemist.

Additional information:
  • Cadmium was discovered by Friedrich Stromeyer in 1817 from an impurity in zinc carbonate.
  • He analyzed a bottle in an apothecary’s shop that contained zinc caronate.
  • He noted that these particular samples turned yellow when heated, while pure zinc carbonate does not.
  • He was persistent enough to follow this observation through and he eventually isolated some cadmium metal.
  • Storage batteries using cadmium as one element have much longer lives than those using lead elements; and they have other advantages with respect to weight and the ability to be stored in a discharged condition.
Name in other languages:
French: cadmium
German: Cadmium
Italian: cadmio
Spanish: cadmio

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Symbol: Ca
Atomic number: 20
Year discovered: 1808
Discovered by: Sir Humphry Davy (1778-1829), an English chemist.

Additional information:
  • Compounds such as lime (calcium oxide) were prepared by the Romans in the first century under the name calx.
  • Literature dating back to about 975 A.D. notes that plaster of Paris (calcium sulphate, dehydrated gypsum) was useful for setting broken bones.
  • Other calcium compounds used in early times include limestone (calcium carbonate).
  • Calcium metal was not isolated until 1808.
  • After learning that Berzelius and Pontin prepared calcium amalgam by electrolyzing lime in mercury, Sir Humphry Davy was able to isolate the impure metal.
  • He did this by the electrolysis of a mixture of lime and mercuric oxide.
  • Calcium metal was not available in large amounts until the beginning of the 20th century.
Name in other languages:
French: calcium
German: Calcium
Italian: calcio
Spanish: calcio

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Symbol: Cf
Atomic number: 98
Year discovered: 1950
Discovered by: Glenn Theodore Seaborg (1912-1999), American physicist, Albert Ghiorso (born July 15, 1915), and Kenneth Street, in Berkeley, California.

Additional information:
  • Metallic californium should be electropositive, reactive, and silver-colored like other actinide metals.
  • Californium is a synthetic chemical element not found in nature.
  • The discoverers suggested the name californium to honor the state and the university where the work was done.
Name in other languages:
French: californium
German: Californium
Italian: californio
Spanish: californio

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Symbol: C
Atomic number: 6
Year discovered: Known since ancient times although not recognized as an element until much later.
Discovered by: Unknown

Additional information:
  • Most of the energy of our bodies, as well as that which drives our machines, is supplied by the oxidation of carbon and its compounds.
  • Every form of animal and plant life requires carbon for survival.
  • Plants obtain it from the carbon dioxide in the air, converting carbon dioxide and water into carbohydrates in the process of photosynthesis.
  • Animals consume the carbohydrates, returning carbon dioxide to the atmosphere by the processes of exhalation and excretion and the decomposition of their bodies under bacterial action after death.
  • This endless chain linking animal and plant life is known as the carbon cycle.
  • Three of the important forms of carbon are diamond, graphite, and black carbon.
  • Diamond is the hardest substance found in nature, but in 1957, a new substance, borazon (cubic boron nitride), was synthesized.
  • It is as hard as diamond and scratches it with ease.
  • More than 1 000 000 compounds of carbon are believed to have been discovered; the exact number never has been determined.
  • It is definitely known; however, that there are more compounds of carbon than of all other elements combined.
  • Carbon as charcoal, soot, and coal has been used since prehistoric times.
Name in other languages:
French: carbone
German: Kohlenstoff
Italian: carbonio
Spanish: carbono

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Symbol: Ce
Atomic number: 58
Year discovered: 1803
Discovered by: Baron Jöns Jakob Berzelius (1779-1848), a Swedish chemist, and Wilhelm Hisinger (1766-1852), a Swedish mineralogist, working together; and independently by Martin Heinrich Klaproth (1743-1817), a German chemist.

Additional information:
  • Contracted from cereium, a name coined by the Swedish chemist Baron Jöns Jakob Berzelius who, at first, thought this element should be Atomic Number 72.
  • Cerium is malleable and ductile and is used in porcelain, glass, and alloys.
  • It reacts rapidly with boiling water, liberating hydrogen; and in wire form, it burns brilliantly when heated.
  • Cerium and its compounds have a number of practical applications.
  • Tetravalent (ceric) salts, that are powerful but stable oxidizing agents, are used in analytical chemistry to determine oxidizable substances such as ferrous iron.
  • The dioxide is employed in the optics industry for fine polishing of glass and as an opacifier in porcelain coatings.
  • Cerium nitrate is used in the manufacture of Welsbach incandescent gas mantles; while other salts are used in the ceramic, photographic, and textile industries.
Name in other languages:
French: cérium
German: Cer
Italian: cerio
Spanish: cerio

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Symbol: Cs
Atomic number: 55
Year discovered: 1860
Discovered by: Gustav Robert Kirchhoff (1824-1887), a German physicist, and Robert Wilhelm Bunsen (1811-1899), a German chemist.

Additional information:
  • Cesium was discovered spectroscopically by Robert Wilhelm Bunsen and Gustav Robert Kirchhoff in 1860 in mineral water from Durkheim, Germany.
  • Their identification was based upon two bright blue lines of unknown origin in the flame spectra of certain mineral water concentrates.
  • Chemically, it is very similar to the other members of the alkali group (lithium, sodium, potassium, and rubidium); and as such, its earlier discovery was overlooked not merely because of its scarcity but through confusion with potassium.
  • Its principal value is in photoelectric cells where advantage is taken of the fact that cesium, in common with other alkali metals, emits electrons when illuminated by visible light.
  • For the same reason it is widely used in the pickup tubes of television cameras.
  • Cesium is the most reactive of all metals, melting and inflaming spontaneously on exposure to air and decomposing water with explosive violence.
  • Each element on the periodic table is known to vibrate at a distinct frequency.
  • The steady pulse of atomic vibrations can keep time far more accurately than any other kind of clock.
  • Cesium is the element used in atomic clocks. In one second, a cesium atom vibrates more than nine billion times.
  • In 1949, scientists at the U. S. National Bureau of Standards used previous research to build the first atomic clock.
  • Now there is an eighth model of the atomic clock that is being constructed at the National Institute of Standards and Technology in Boulder, Colorado.
  • In the quest for greater time precision, physicists have made a quantum leap forward with the discovery that the oscillations of cesium-133 atoms, subjected to microwave radiation, could be manipulated to allow a time calculation with an error of one second every 1.4 million years.
  • The vibrations in an atom are far more consistent and accurate than any other time-keeping device known to scientists.
  • Atomic clock vibrations are said to be incomprehensibly fast. In fact, the unit of time we know as a “second” was defined in 1967 using the cesium atomic clock.
  • The inherent frequency of cesium atoms became the official international unit of time, now called Universal Coordinated Time (UCT).
  • No longer was time measured on the movements of the earth, a second being a fraction of a day, but by the vibrations of an atom; a second being the time it took a cesium atom to oscillate precisely 9 192 631 770 times.
  • The second quickly became the physical quantity most accurately measured by scientists.
  • Atomic time has replaced “earth time” as the world’s official timekeeper.
  • The first atomic clock was based on the ammonia atom, which quickly was replaced with the much more accurate cesium atom.
  • Research aimed at developing an atomic clock focused first on microwave resonances in the ammonia molecule.
  • Attention shifted almost immediately to more-promising, atomic-beam devices based on cesium.
  • Just five grams of cesium, a metal with a low melting point, will last about 10 years.
  • Clocks are improving in accuracy at better than a factor of ten every ten years which means that today’s atomic clock is considered “a million times more accurate than the one built in 1949.”
  • GPS, Global Positioning System, technology is based on atomic clock technology. Every GPS unit has an atomic clock on board, and the unit uses satellites and ground stations to orient and determine its precise location.
  • The U.S. Air Force started launching satellites for the GPS in the late 1970’s so they could increase rocket and artillery accuracy, and to improve precise land, sea and air navigation regardless of weather conditions.
  • Twenty-four satellites, some equipped with three atomic clocks, others with four, rocketed into orbit 12 000 miles above the earth where they remain to this day, transmitting their positions earthward with precise timing signals generated by the atomic clocks on board.
  • Far below, GPS receivers can pick up the signals, then electronically calculate latitude, longitude, altitude, speed and compass direction anywhere in the world.
  • Fully operational for military use by 1994, the basic system has since become available to the general public resulting in practical use for supertanker captains and recreational boaters, commercial and private aircraft pilots, surveyors, hikers, and even in automobiles.
  • Without the atomic clocks at each location, the GPS unit would be useless. Extremely accurate time measurements are required to triangulate between satellites, and to determine an exact location.
  • As for telecommunications, people are edging along a continuum of sending more and more data through telecommunications lines, faster and faster.
  • If the channel the data pass through is synchronized in time at both ends, the data can travel much more swiftly. The only way to synchronize these optical fibers with absolute precision is to use atomic clocks.
  • Scientists have long realized that atoms (and molecules) have resonances; each chemical element and compound absorbs and emits electromagnetic radiation at its own characteristic frequencies.
  • These resonances are inherently stable over time and space. It is said that an atom of hydrogen or cesium here today is exactly like one a million years ago or in another galaxy.
  • As we continue our “Walk Through Time”, we will see how agencies such as the National Institute of Standards and Technology, the U.S. Naval Observatory, and the International Bureau of Weights and Measures in Paris assist the world in maintaining a single, uniform time system.
  • In fact, it is claimed that within the next few years, new clocks, based on a process that uses supercooled atoms, and achieving an accuracy of just one second lost in 313 million years, will be operational.
  • At the National Institute of Standards and Technology, in Bolulder, Colorado, scientists are working on an even more advanced atomic clock, one that functions independently of gravity, a distorting variable in this system of time management.
  • In order to accomplish this, a working model of this clock will operate outside gravity in space.
  • The clock is slated to be placed aboard the Internatioinal Space Station in 2004.
  • Horologists agree that even with a clock that will miss no more than a second every trillion years, unbuilt as yet but conceivable, time will remain elusive and mysterious.
  • Some of the information for this section came from the article, “Taking the Measure of Time”, by Per Ola and Emily D’Aulaire in the December, 1999, issue of Smithsonian, pages 52-64 (specifically from page 64).
Name in other languages:
British: caesium
French: césium
German: Cäsium
Italian: cesio
Spanish: cesio

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Symbol: Cl
Atomic number: 17
Year discovered: 1774 or 1810
Discovered by: Karl Wilhelm Scheele (1742-1786), a Swedish chemist, and credit is given to Sir Humphry Davy for showing that chlorine was an element not an oxygen compound.

Additional information:
  • Karl Wilhelm Scheele discovered many simple compounds from plants and animals, to say nothing of such poisonous gases as hydrogen fluoride, hydrogen sulfide, and hydrogen cyanide.
  • Scheele was also involved in the discovery of a number of elements, though he never managed to get undisputed credit for a single one of them.
  • By 1774, he had done most of the preliminary work that led to the discovery of the element manganese.
  • His friend, the Swedish mineralogist Johan Gottlieb Gahn (1745-1818); however, completed the final step and got credit for the discovery.
  • Again, in 1774, Scheele isolated the gas chlorine, which was unusual in that it was not colorless.
  • Chlorine is greenish-yellow and its name is derived from the Greek word for “green”.
  • Scheele’s problem was that he didn’t recognize chlorine to be an element because he thought it was a combination of some substance with oxygen.
  • Since Scheele thought the resulting gas contained oxygen, Sir Humphry Davy proposed and confirmed chlorine to be an element in 1810, and he also named the element.
  • Scheele obtained chlorine through the reaction of the mineral pyrolusite (manganese dioxide) with hydrochloric acid (then known as muriatic acid).
  • Davy had worked with hydrochloric acid (a strong acid) and he showed that it contained no oxygen.
  • This was the final blow to the general assumption that oxygen was essential to acids.
  • Hydrochloric acid did contain chlorine, and Scheele thought chlorine was an oxygen-containing compound.
  • In 1810, Davy showed this was not true, and that chlorine was an element.
  • For this reason, Davy, rather than Scheele usually receives credit for the discovery of chlorine.
Name in other languages:
French: chlore
German: Chlor
Italian: cloro
Spanish: cloro

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Symbol: Cr
Atomic number: 24
Year discovered: 1797
Discovered by: Nicolas Louis Vauquelin (1763-1829), a French chemist; Count Antoine-Fransois de Klein, French chemist; and René-Just Haüy (1743-1822), a French mineralogist.

Additional information:
  • In a mid 18th century analysis of “red lead” (crocoite) from Siberia showed that it contained a great deal of lead, but there was also another material that was eventually identified as chromium oxide.
  • Chromium oxide was discovered in 1797 by Louis-Nicholas Vauquelin, who produced the metal itself in the following year.
  • Starting from crocoite, the procedure was to powder the mineral and to precipitate the lead out through its reaction with hydrochloric acid. The residue was chromium oxide.
  • Heating this oxide in an oven resulted in the metal itself.
Name in other languages:
French: chrome
German: Chrom
Italian: cromo
Spanish: cromo

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Symbol: Co
Atomic number: 27
Year discovered: 1735
Discovered by: Georg Brandt (1694-1768), a Swedish chemist.

Additional information:
  • Minerals containing cobalt were of value to the early civilizations of Egypt and Mesopotamia for coloring glass deep blue.
  • In China, cobalt ores were used to produce the blue colors of the porcelains of the Ming dynasty.
  • Cobalt was announced to be an element by Georg Brandt about 1735 (or possibly 1739).
  • In 1737, a Swedish chemist, Georg Brandt (1694-1768), investigated the blue ore and managed to obtain a metal from it but one that was definitely not copper.
  • He had been trying to demonstrate that the blue color of glass was the result of a new element, called cobalt, rather than bismuth, an element often found in the same locations as cobalt.
  • It puzzled miners that blue mineral resembling copper ore did not yield copper when smelted.
  • The miners assumed that it was copper ore that had been bewitched by kobolds; that is, earth spirits who were thought to be malevolent at times.
  • Brandt gave it the name of the earth spirit, spelling it “cobalt”, and that is still the name of the element.
  • This was the first new element discovered since Brand’s discovery of phosphorus previously in 1669.
  • Since phosphorus is not a metal, cobalt was also the first metal to be discovered that was not known to the ancients or to the medieval alchemists.
  • Brandt was perhaps the first important chemist to be completely free of any alchemical taint, and after him the discovery of new elements has continued until recent times.
  • Cobalt is now being used to impart a blue color to structural glass, pharmaceutical, perfume, and decorative bottles, as well as optical filter glasses.
  • Another principal use is in alloys, particularly in “superalloys”, as those in jet engines.
  • It is also used in the preparation of alloys of high magnetic strength for permanent magnets. and in high-speed tool steels, hot-work tool steels, and high-carbon, high-chromium, and cold-work steels.
  • Small quantities of cobalt salts are used to correct mineral deficiencies in livestock and additives in varnish and inks.
Name in other languages:
French: cobalt
German: Cobalt
Italian: cobalto
Spanish: cobalto

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Symbol: Cu
Atomic number: 29
Year discovered: Known since ancient times
Discovered by: Unknown

Additional information:
  • The discovery of copper dates from prehistoric times.
  • There are reports of copper beads dating back to 9000 B.C. found in Iraq.
  • Methods for refining copper from its ores were discovered around 5000 B.C. and a 1000 or so years later it was being used in pottery in North Africa.
  • Part of the reason for use so early in history is simply that it was relatively easy to shape.
  • It is somewhat too soft for many tools so about 5000 years ago it was discovered that when copper is mixed with other metals the resulting alloys are harder than copper itself.
  • As examples, brass is a mixture of copper and zinc while bronze is a mixture of copper and tin.
  • About 3000 B.C., copper was produced extensively on the island of Cyprus.
  • These copper deposits were so great and so highly prized that control of the island passed in succession to the Egyptians, Assyrians, Phoenicians, Greeks, Persians, and the Romans.
  • The Roman supply of the metal came almost entirely from that island, and the material was known as aes cyprium (“ore of Cyprus”), which was shortened to cyprium and later corrupted to cuprum.
  • From this term comes the English name “copper”.
  • The first two letters of the Latin name, of course, constitute the chemical symbol Cu.
Name in other languages:
French: cuivre
German: Kupfer
Italian: rame
Spanish: cobre

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Symbol: Cn
Atomic number: 96
Year discovered: 1944
Discovered by: Glenn Theodore Seaborg (1912-1999), American physicist, Ralph A. James, and Albert Ghiorso (born July 15, 1915) at the University of Chicago.

Additional information:
  • Curium was identified by Seaborg and others in 1944 as a result of helium ion bombardment of the plutonium isotope.
  • Three years later visible amounts of the hydroxide were isolated by Werner and Perlman.
  • In 1951, the same workers prepared curium in its elemental form for the first time.
Name in other languages:
French: curium
German: Curium
Italian: curio
Spanish: curio

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Symbol: Db
Atomic number: 105
Year discovered: 1967 in Russia and at Berkeley, California.
Discovered by: Workers at the Nuclear Institute at Dubna, Russia; and the University of California, Berkeley, USA.

Additional information:
  • At one time, dubnium had the proposed name of “hahnium” in honor of Otto Hahn (1879-1968), a German physical chemist.
  • Dubna is one of Russia's planned “science cities”, its existence depends on the Joint Institute for Nuclear Research which consists of seven laboratories, employing scientists from many countries.
  • Dubnium apparently was synthesized by Russian and American workers independently by bombardment technologies.
  • Its actual isolation as a free element has not been accomplished.
  • In 1967, Flerov reported element 105 after experiments at the Joint Research Institute in Russia.
  • In 1970, Ghiorso and others announced their synthesis of dubnium at Berkeley, California.
  • This element was previously named, unnilpentium, (Unp) and is the Latin equivalent of “105”; but it was changed because scientists, and others, thought it was too complicated to remember.
  • In addition to unnilpentium (Unp), the proposed names for Element 105 before the official name was chosen by the International Union of Pure and applied Chemistry were hafnium (Ha) and nielsbohrium (Ns).
Name in other languages:
French: dubnium
German: Dubnium
Italian: dubnio
Spanish: dubnio

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Symbol: Dy
Atomic number: 66
Year discovered: 1866
Discovered by: Paul-Émile Lecoq de Boisbaudran (1838-1912), a French chemist.

Additional information:
  • A little dysprosium oxide was identified in 1886 by Paul-Émile Lecoq de Boisbaudran as an impurity in erbia (erbium oxide), but the element itself was not isolated at that time.
  • Boisbaudran, who had already isolated gallium and samarium, was working on a rare earth ore containing holmium when he discovered that it contained small amount of still another rare earth element, which he named “dysprosium”, from a Greek word meaning “hard to get at”.
  • Neither the oxide nor the metal was available in relatively pure form until the 1950’s following the development of ion-exchange separation and metallographic reduction techniques.
  • Its compounds have been used as catalysts in the oil refining industry, as compounds in some electronic equipment, and as phosphor activators.
Name in other languages:
French: dysprosium
German: Dysprosium
Italian: disprosio
Spanish: disprosio

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Symbol: Es
Atomic number: 99
Year discovered: 1952
Discovered by: Albert Ghiorso (born July 15, 1915) and co-workers; at Argonne, Los Alamos, New Mexico and the University of California at Berkeley.

Additional information:
  • Einsteinium was identified by Ghiorso and others at the University of California in Berkeley, California, in 1952.
  • It was found in radioactive debris from the first large thermonuclear bomb explosion, which took place in the Pacific on November, 1952.
  • In 1961, a sufficient amount of einsteinium was produced to permit separation of a macroscopic amount of isotope Es.
Name in other languages:
French: einsteinium
German: Einsteinium
Italian: einsteinio
Spanish: einsteinio

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