Name a chemical and its origin or where it comes from?

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Offline Chemistry4me

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Name a chemical and its origin or where it comes from?
« Reply #100 on: 14/01/2009 22:42:53 »
Silver, white, lustrous metallic element that conducts heat and electricity better than any other metal. Chemically silver is not very active. It is insoluble in dilute acids and in alkalis but dissolves in concentrated nitric or sulphuric acid, and it does not react with oxygen or water at ordinary temperatures. Sulphur and sulphides attack silver, and tarnishing is caused by the formation of silver sulphide on the surface of the metal. Eggs, which contain a considerable quantity of sulphur as a constituent of protein, tarnish silver extremely quickly. Small amounts of sulphide, which occurs naturally in the atmosphere and which, as hydrogen sulphide (H2S), is added to natural gas used domestically, tarnish silver. Silver ranks about 66th among elements in natural abundance in crustal rocks. It occurs in the pure state to a small extent. Pure silver is also found associated with pure gold in the form of an alloy known as electrum, and considerable amounts are recovered in the processing of gold.

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« Reply #101 on: 16/01/2009 02:03:56 »
Cadmium, silvery-white metallic element that can easily be shaped. The element ranks about 65th in natural abundance among the elements in the Earth's crust. When heated, cadmium burns in air with a bright light, forming the oxide CdO. Cadmium may be electrolytically deposited as a coating on metals, chiefly iron or steel, on which it forms a chemically resistant coating. Cadmium lowers the melting point of metals with which it is alloyed; it is used with lead, tin, and bismuth in the manufacture of fusible metals for automatic sprinkler systems, fire alarms, and electric fuses. An alloy of cadmium with lead and zinc is used as a solder for iron. Cadmium salts are used in photography and in the manufacture of fireworks, rubber, fluorescent paints, glass, and porcelain. Cadmium has been used as a control or shielding material in atomic energy plants because of its high absorption of low-energy neutrons. Cadmiun sulphate (3CdSO4•8H2O) is used as an astringent. Cadmium sulphide (CdS), formed as a bright yellow precipitate when hydrogen sulphide is passed through a solution of cadmium salt, is an important pigment known as cadmium yellow. The selenide CdSe is also used as a pigment. Cadmium and solutions of its compounds are highly toxic, with cumulative effects similar to those of mercury poisoning.

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« Reply #102 on: 16/01/2009 02:04:44 »
Indium, soft, malleable, silvery-white metallic element. The element is in group 13 of the periodic table. It ranks 63rd in order of abundance of the elements in the surface of the Earth. Indium never occurs as a free metal and is usually found as the sulphide In2S3; in certain zinc blendes; and in tungsten, tin, and iron ores. It is used as an alloying agent with non-ferrous metals, in bearing alloys, and in nuclear-reactor control rods. Certain indium compounds have unique semiconductor properties.

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« Reply #103 on: 17/01/2009 00:05:33 »
Tin, metallic element that has been used by people since ancient times. Tin is in group 14 of the periodic table. Tin forms stannic acid, H2SnO4, when heated in air or oxygen at high temperatures. It dissolves in hydrochloric acid to form stannous chloride, SnCl2, and in aqua regia to form stannic chloride, SnCl4, and it reacts with sodium hydroxide solution to form sodium stannite and hydrogen gas. In cold and very dilute nitric acid, tin dissolves to form stannous nitrate and ammonium nitrate; in concentrated nitric acid, it produces metastannic acid, H2SnO3. The two hydroxides of tin, Sn(OH)2 and Sn(OH)4, are produced by adding a soluble hydroxide to solutions of stannous and stannic salts. Stannous oxide, SnO, a black insoluble powder, is obtained by heating stannous oxalate in the absence of air. In the presence of air, stannous oxide burns to form the dioxide, or stannic oxide, SnO2, a white insoluble solid. Tin is a widely sought metal and is used in hundreds of industrial processes throughout the world. In the form of tinplate, it is used as a protective coating for copper vessels, various metals used in the manufacture of tin cans, and similar articles. Tin is important in the production of the common alloys bronze (tin and copper), solder (tin and lead), and type metal (tin, lead, and antimony). It is also used as an alloy with titanium in the aerospace industry and as an ingredient in some insecticides. Stannic sulphide, known also as mosaic gold, is used in powdered form for bronzing articles made of plaster of paris or wood.

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« Reply #104 on: 17/01/2009 00:06:57 »
Antimony, bluish-white, brittle, semi-metallic element. Antimony generally shows the properties of a metal, but sometimes shows those of a non-metal. It exists in several distinctly different physical forms, the most common of which is metallic in appearance. Antimony ranks about 64th in natural abundance among the elements in crustal rock. It occasionally occurs as a free element, usually associated with silver, arsenic, or bismuth. It crystallizes in the hexagonal system but crystals are rarely found. It has a hardness of 3. The principal ore of antimony is stibnite, a sulphide of antimony. Among the important compounds of antimony are tartar emetic, a double tartrate of antimony and potassium used as a medicinal agent; red antimony sulphide, used on safety matches and in vulcanizing rubber; glass of antimony, a mixture of antimony sulphide and oxide, used as a yellow pigment in glass and porcelain; and butter of antimony, antimony trichloride, used for bronzing steel, as a mordant in dyeing, and as a caustic in medicine.

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« Reply #105 on: 18/01/2009 04:26:56 »
Tellurium (Latin, tellus, “Earth”), silver-white, brittle, semimetallic element. Tellurium is a comparatively stable element, insoluble in water and hydrochloric acid but soluble in nitric acid and aqua regia. Tellurium reacts with an excess of chlorine to form tellurium dichloride, TeCl2, and tellurium tetrachloride, TeCl4. It is oxidized by nitric acid to produce tellurium dioxide, TeO2, and by chromic acid to produce telluric acid, H6TeO6. In combination with hydrogen or certain metals, it forms tellurides such as hydrogen telluride, H2Te, and sodium telluride, Na2Te. Tellurium ranks about 78th in natural abundance among the elements in the Earth's crust. It occurs in the pure state or is found in combination with gold, silver, copper, lead, and nickel in such minerals as sylvanite, petzite, and tetradymite. Occasionally it is found in rocks as tellurite (or tellurium dioxide), TeO2. The slime from lead and copper refineries and the flue dust from telluride-gold deposits are the principal commercial sources. It is also prepared by reduction of telluric oxide, forming a greyish-white, metallic powder. Tellurium is used in the manufacture of rectifiers and thermoelectric devices and in semiconductor research. With other organic substances, it is employed as a vulcanizing agent in the processing of natural and synthetic rubber; and in antiknock compounds for petrol. It is used also to impart a blue colour to glass. Colloidal tellurium is an insecticide, germicide, and fungicide.

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« Reply #106 on: 18/01/2009 04:28:42 »
Iodine, chemically reactive element, a blue-black solid at room temperature. In group 17 of the periodic table. Unlike the lighter halogens, iodine is a crystalline solid at room temperature. The lustrous, blue-black, soft substance sublimes when heated, giving off a violet vapour with a stinging odour like that of chlorine. The vapour rapidly condenses again on a cold surface. The only isotope that occurs in nature is stable, but several radioactive ones have been produced artificially. The element in its pure form is poisonous. Iodine, like all halogens, is chemically active. It is only slightly soluble in water, but it dissolves readily in an aqueous solution of potassium iodide. It is also soluble in alcohol, chloroform, and other organic reagents. Iodine is a relatively rare element, ranking about 62nd in abundance on Earth, but its compounds are widespread in sea water, soil, and rocks. Iodine is medicinally very important because it is an essential trace element, present in a hormone of the thyroid gland that is involved in growth-controlling and other metabolic functions. Without iodine, stunted growth and conditions such as goitre can result. Thus in areas where iodine is not sufficiently abundant naturally, iodine-containing salt serves to make up the deficit. In medicine, iodine-alcohol solutions and iodine complexes have been used as antiseptics and disinfectants. More broadly, various iodine compounds find use in photography, the making of dyes, and cloud-seeding operations. In chemistry, various iodine compounds serve as strong oxidizing agents, among other uses.

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« Reply #107 on: 19/01/2009 03:14:32 »
Xenon, symbol Xe, colourless, odourless gaseous element with an atomic number of 54. In group 18 of the periodic table, xenon is one of the noble gases. Xenon was discovered in England by William Ramsay and Morris Travers on July 12, 1898, shortly after their discovery of the elements krypton and neon. Naturally occurring xenon is made of nine stable isotopes, the most of any element with the exception of tin, which has ten. It was formerly believed to be chemically inert, but since 1962 several compounds of xenon have been prepared. Xenon hexafluoroplatinate was the first chemical compound of xenon. Xenon is used principally in such lighting devices as high-speed photographic tubes. Xenon is present in the atmosphere in minute amounts.

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« Reply #108 on: 19/01/2009 03:16:15 »
Caesium, symbol Cs, white, soft, chemically reactive metallic element. In group 1 of the periodic table, caesium is one of the alkali metals. Caesium ranks about 46th in natural abundance among the elements in crustal rocks. The natural source yielding the greatest quantity of caesium is the rare mineral pollux (or pollucite). Caesium also occurs in lepidolite, carnallite, and certain feldspars. It is extracted by separating the caesium compound from the mineral, transforming the compound thus obtained into the cyanide, and electrolysis of the fused cyanide. Caesium can also be obtained by heating its hydroxides or carbonates with magnesium or aluminium and by heating its chlorides with calcium. Commercial caesium usually contains rubidium, with which it usually occurs in minerals and which resembles it so closely that no effort is made to separate them. Like potassium, caesium oxidizes readily when exposed to air and is thus used to remove residual oxygen from radio vacuum tubes. Because of its property of emitting electrons when exposed to light, it is used in the photosensitive surface of the cathode of the photoelectric cell. The radioactive isotope caesium-137, which is produced by nuclear fission, is a useful by-product of atomic-energy plants. Caesium-137 emits more energy than radium and is used in medical and industrial research, for example as an Isotopic Tracer.

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Name a chemical and its origin or where it comes from?
« Reply #109 on: 19/01/2009 14:30:42 »
Rubidium and Caesium in water:
http://www.youtube.com/watch?v=sNdijknRxfU
« Last Edit: 19/01/2009 14:33:03 by lightarrow »

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« Reply #110 on: 19/01/2009 21:47:42 »
Barium, soft, silvery, highly reactive metal. Barium was first isolated in 1808 by the English scientist Sir Humphry Davy. The element reacts vigorously with water and rapidly corrodes in moist air. In fact, the element is so reactive that it only occurs in nature as a compound. Its most important compounds are the minerals barium sulphate and barium carbonate (witherite), BaCO3. An alkaline earth metal, barium is the 14th most common element, making up 1/2000th of the crust of the Earth. Barium metal has few practical applications, although it is sometimes used in coating electrical conductors in electronic apparatus and in car ignition systems. Barium sulphate (BaSO4) is used as a filler for rubber products, in paint, and in linoleum. Barium nitrate is used in fireworks, and barium carbonate in rat poisons. A form of barium sulphate, which is opaque to X-rays, is used for the X-ray examination of the gastrointestinal tract

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« Reply #111 on: 19/01/2009 21:49:48 »
Lanthanum (Greek lanthanein, “to escape notice”). Lanthanum is often regarded as the first member of the lanthanide series, to which it gives its name. It burns in air at about 450° C to form lanthanum oxide, La2O3. It forms colourless trivalent salts, including one of the strongest trivalent bases, which is used by analytical chemists. It generally occurs with other rare earth elements in such minerals as apatite and monazite and in certain kinds of calcite and fluorspar. It is fairly common, ranking 28th in order of abundance of the elements in the Earth's crust. Impure lanthanum is used in alloys such as misch metal, of which lanthanum is a major constituent. Cigarette-lighter flints are made from this alloy. Lanthanum oxide is used in certain types of optical glass.

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« Reply #112 on: 20/01/2009 23:55:24 »
Cerium, soft, grey metallic element that is the most abundant of the rare earth elements. Cerium ranks 26th in natural abundance among the elements in the Earth's crust. It occurs with other rare earth metals in monazite, which is found widely distributed worldwide. It also occurs in the minerals cerite, found in Sweden, and allanite, found in Greenland and the United States. Metallic cerium is chiefly found in an iron alloy that composes the flints used in cigarette lighters. Ceric oxide was formerly employed in the manufacture of gas mantles. Compounds of cerium are employed in small quantities in the manufacture of glass, ceramics, arc-lamp electrodes, and photoelectric cells. Cerous nitrate has been used medicinally in the treatment of seasickness and chronic vomiting. Ceric sulphate is used as an oxidizing agent.

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« Reply #113 on: 20/01/2009 23:56:33 »
Praseodymium, silvery metallic element with an atomic number of 59. Praseodymium is one of the rare earth elements in the lanthanide series of the periodic table. Praseodymium was discovered in 1885 by the German chemist Carl Auer von Welsbach, who separated it from neodymium. A mixture of the two elements had formerly been considered a single element, called didymium. Praseodymium is a paramagnetic metal that corrodes rapidly in moist air. It forms green trivalent salts. Praseodymium is widely distributed in nature and ranks 37th in order of abundance of the elements in the crust of the Earth. It is found in cerite and other rare earth minerals. It is used, with small amounts of other rare earth metals, in magnesium alloys and in misch metal, an alloy used for cigarette-lighter flints and as a deoxidizer in alloys and vacuum tubes. A mixture of praseodymium and neodymium is used to tint goggles for welders.

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« Reply #114 on: 21/01/2009 22:38:02 »
Neodymium, silvery metallic element with an atomic number of 60. Neodymium is one of the rare earth elements in the lanthanide series of the periodic table. Neodymium and praseodymium had previously been regarded as a single element, called didymium. Neodymium ranks 27th in order of abundance of the elements in the Earth's crust. It forms trivalent salts, which are rose-red or reddish-violet in colour. The metal's oxide, Nd2O3, is used in the glass of colour-television tubes to increase contrast, and in lasers

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« Reply #115 on: 21/01/2009 22:38:48 »
Promethium, radioactive metallic element with an atomic number of 61. Promethium is one of the rare earth elements in the lanthanide series of the periodic table. Promethium was one of the last elements to be identified. In 1926 evidence from spectroscopic analysis indicated the existence of the element in various minerals, and the names illinium and florentium were proposed for the element. The fission of uranium is known to produce several radioactive isotopes with atomic number 61. Isotopes with mass numbers from 134 to 155 have been investigated. The most stable isotope of promethium, which has a mass number of 147, has a half-life of 2.6 years; visible amounts of this isotope have been prepared. The metal has been used in atomic batteries and as a beta-particle source in thickness gauges.

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« Reply #116 on: 22/01/2009 00:36:47 »
Please stick to the order the elements appear in the periodic table..

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Offline erickejah

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« Reply #117 on: 22/01/2009 01:48:08 »
Please stick to the order the elements appear in the periodic table..
done

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« Reply #118 on: 22/01/2009 20:49:22 »
Samarium, hard, brittle, lustrous metallic element. Samarium is one of the rare earth elements in the lanthanide series of the periodic table. The metal ignites in air at about 150°C. Like other rare earth metals, it is found in minerals such as cerite, gadolinite, and samarskite. It is 40th in order of abundance of the elements in the Earth's crust. Samarium forms chiefly trivalent compounds; the salts are pale yellow in colour. Samarium oxide is used in the control rods of some nuclear reactors.

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« Reply #119 on: 22/01/2009 20:50:01 »
Europium, soft, silvery metallic element that is among the least abundant of the rare earth elements. Europium is in the lanthanide series of the periodic table.It ranks 50th in order of abundance of the elements in the Earth's crust; it occurs in monazite, bastnaesite, and other rare earth minerals, as well as in fission products of uranium, thorium, and plutonium. Europium is used as a phosphor activator. The screen of a colour-television tube is treated with europium, which, when bombarded with electrons, produces the colour red. Because it readily absorbs neutrons, europium is used in the control of nuclear fission in reactors

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« Reply #120 on: 22/01/2009 23:12:17 »
Rubidium and Caesium in water:
http://www.youtube.com/watch?v=sNdijknRxfU
I wonder how much Caesium cost??

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« Reply #121 on: 22/01/2009 23:15:24 »
Have a look here

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« Reply #122 on: 23/01/2009 20:54:08 »
Gadolinium, silvery-white metallic element. Gadolinium is one of the rare earth elements in the lanthanide series of the periodic table. Gadolinium occurs with other rare earth elements in many minerals, such as samarskite, gadolinite, monazite, and some varieties of Norwegian ytterspar. It is the 41st element in order of abundance in the crust of the Earth. Gadolinium oxide was first separated from other rare earth elements by the Swiss chemist Jean de Marignac in 1880. The oxide and many salts of gadolinium have been prepared. Gadolinium oxide is white and the salts are colourless. Because gadolinium has the largest known cross section, or stopping power, for neutrons of any element, it is used as a component of control rods in nuclear reactors. Like the other rare earth elements, it is used in electronic apparatus such as capacitors and masers; in metal alloys; in high-temperature furnaces; and in apparatus for magnetic cooling.

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« Reply #123 on: 23/01/2009 20:55:12 »
Terbium is one of the rare earth elements in the lanthanide series of the periodic table. It ranks about 58th in natural abundance among the elements in crustal rock. It occurs in minute quantities as a white oxide known as terbia, Tb2O3, in such minerals as gadolinite. Terbium has potential applications in alloys, refractory (high-temperature) materials, and electronic apparatus.

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« Reply #124 on: 25/01/2009 01:06:47 »
Dysprosium, metallic element. Dysprosium is one of the rare earth elements in the lanthanide series of the periodic table. Dysprosium is 42nd in abundance among the elements in the Earth's crust. The compounds of dysprosium are found in gadolinite, xenotime, euxenite, and fergusonite in Norway, the United States, Brazil, India, and Australia. Its salts are either yellow or yellow-green in colour, the most common being a chloride (DyCl3), a nitrate (Dy(NO3)3•5H2O), and a sulphate (Dy2(SO4)3•8H2O). The salts of dysprosium have an extremely high magnetic susceptibility. Dysprosium usually occurs as the white oxide dysprosia (Dy2O3), with erbium and holmium, two other rare earth elements. Dysprosia is sometimes used in the control rods of nuclear reactors

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« Reply #125 on: 25/01/2009 01:07:23 »
Holmium, silver-coloured metallic element. Holmium is one of the most paramagnetic substances known. The element has few practical applications, though it has been used in some electronic devices and as a catalyst in industrial chemical reactions. Holmium is one of the least abundant of the rare earth metals, ranking 55th in order of abundance of the elements in the Earth's crust. Holmium occurs in gadolinite and other minerals containing rare earths. Holmium oxide, Ho2O3, a greyish-white powder, and a few salts, such as the sulphate, have been prepared.

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« Reply #126 on: 26/01/2009 00:22:20 »
Erbium, metallic element. The Swedish chemist Carl Gustav Mosander discovered erbium in 1843. Erbium occurs mostly in the same minerals and in the same areas as dysprosium. One of the rare earth elements, erbium is 43rd in abundance among the elements of the Earth's crust. The atomic weight of erbium is 167.26. The element melts at about 1530°C , boils at about 2870°C , and has a relative density of 9.1. Metallic erbium has a bright silvery lustre. Erbium oxide, Er2O3, is a rose-red compound slowly soluble in many mineral acids, forming a series of rose-coloured salts, solutions of which have a sweet, astringent taste. Erbium is used in experimental optical amplifiers that amplify light signals sent along fibre-optic cables

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« Reply #127 on: 26/01/2009 00:24:21 »
Thulium, silver-grey metallic element that is the rarest of the rare earth elements. Thulium is in the lanthanide series of the periodic table the atomic number of thulium is 69. Thulim was discovered in 1879 by the Swedish chemist Per Teodor Cleve. Thulium ranks 61st in abundance among the elements in the crust of the Earth and is found in small quantities in such rare earth minerals as euxenite, gadolinite, and blomstrandine. The metal can be isolated by reduction of its oxide, Tm2O3, and is soft, malleable, and ductile. Thulium had little practical application until the development in the 1950s of a small, portable X-ray machine that utilizes artificially radioactive thulium as its X-ray source. Thulium melts at about 1545°C, boils at about 1950°C, and has a relative density of 9.34.

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« Reply #128 on: 26/01/2009 21:44:09 »
Ytterbium, soft, malleable, ductile metallic element that has a bright, silvery lustre. Ytterbium is one of the rare earth elements in the lanthanide series of the periodic table. Ytterbium is reasonably stable but reacts slowly with water to liberate hydrogen. Ytterbium occurs in combination with such minerals as xenotime, euxenite, monazite, and gadolinite. It ranks about 44th in natural abundance among the elements in the Earth's crust. Ytterbium has potential applications in alloys, electronics, and magnetic materials.

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« Reply #129 on: 26/01/2009 21:46:32 »
Lutetium, silvery-white metallic element with an atomic number of 71. Lutetium was discovered independently by two investigators, the French chemist Georges Urbain in 1907 and the Austrian chemist Carl Auer von Welsbach about the same time. It was named by Urbain, who derived the word from Lutetia, the ancient name of Paris. Lutetium occurs in various rare earth minerals, usually associated with yttrium. It was the rarest of the rare earth elements when classified in that group and it ranks 59th in order of abundance of the elements in the Earth's crust. Several trivalent salts are known. A natural radioactive isotope of lutetium that has a half-life of about 30 billion years is used in determining the age of meteorites in relation to the age of the Earth. Lutetium melts at about 1665°C, boils at about 3400°C and has a relative density of 9.84.

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« Reply #130 on: 27/01/2009 21:49:56 »
Hafnium, metallic element that closely resembles zirconium. Hafnium is one of the transition elements of the periodic table. On the basis of a prediction by the Danish physicist Niels Bohr that element 72 would resemble zirconium in structure, they looked for the element in zirconium ores. Hafnium is found in nearly all ores of zirconium and is 45th in order of abundance of the elements in the crust of the Earth. It resembles zirconium so closely in chemical properties and crystal structure that separation of the two elements is extremely difficult. Separation is accomplished most efficiently by means of the ion-exchange technique. Hafnium is used in the manufacture of tungsten filaments. Because of its resistance to high temperatures, it is used with zirconium as a structural material in nuclear power plants.

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« Reply #131 on: 27/01/2009 21:51:42 »
Tantalum, white, ductile, malleable metallic element. Tantalum is one of the transition elements of the periodic table. Tantalum belongs to the group of metals that includes vanadium and niobium. It occurs mainly in the mineral tantalite, FeTa2O6. Tantalum ranks about 53rd among the elements in natural abundance in the Earth's crust. Principal deposits of the metal occur in Australia and Scandinavia. Most tantalum minerals contain some niobium metal, which is separated by solvent extraction or selective-crystallization procedures. Commercially, tantalum is prepared by the electrolysis of fused potassium tantalifluoride or of tantalum compounds dissolved in dilute sulphuric acid. Because it is more resistant than platinum to many corrosive agents, tantalum has largely replaced platinum in standard weights and in laboratory ware. The largest use of tantalum is for capacitors in electronic circuits and rectifiers in low-voltage circuits, such as railway-signalling systems. Because of its resistance to attack by acids of the human body and its compatibility with body tissue, it is used to pin together broken bones. Tantalum is also used in surgical and dental instruments and in chemical heat exchangers. The oxide is an ingredient in special optical glass for aerial camera lenses.

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« Reply #132 on: 28/01/2009 22:53:27 »
Tungsten, symbol W (from the earlier name, wolfram), metallic element that has the highest melting point of any metal. Tungsten is one of the transition elements of the periodic table. Pure tungsten is silver-white in colour and is ductile; the more easily obtained impure form is steel-grey and is hard and brittle. Tungsten is insoluble in hot and cold water and in alcohol, slightly soluble in ammonia and nitric acid, and soluble in hot, concentrated potassium hydroxide. Tungsten ranks 57th in abundance among the elements in the crust of the Earth. It is never found free in nature, but occurs in combination with other metals, notably in the minerals scheelite and wolframite, which are the important tungsten ores. Mines in South Korea, Portugal, Austria, and Australia produce more than half of the world's supply of these ores. To separate the element from its ore, the ore is first fused with sodium carbonate to give sodium tungstate, Na2WO4. The soluble sodium tungstate is then extracted with hot water and treated with hydrochloric acid to yield tungstic acid, H2WO4. The latter compound is washed and dried to produce the oxide WO3, which is reduced by hydrogen in an electric furnace. The resulting fine powder is reheated in moulds in an atmosphere of hydrogen and pressed into bars, which are hammered and rolled at high temperature to compact them and make them ductile. The principal uses of tungsten are as filaments in incandescent lamps, as wires in electric furnaces, and in the production of hard, tenacious alloys of steel. It is used also in the manufacture of spark plugs, electrical contact points, and cutting tools, and as a target in X-ray tubes.

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« Reply #133 on: 28/01/2009 22:54:18 »
Rhenium, rare, silvery-white, metallic element. Rhenium is one of the transition elements of the periodic table. The existence of rhenium and the similarity of its chemical properties to those of the element manganese were predicted in 1871 by the Russian chemist Dmitry Ivanovich Mendeleyev, who named it dvi-manganese. Rhenium metal is very hard; with the exception of tungsten, it is the least fusible of all common metals. Overall, it ranks about 79th in natural abundance among elements in crustal rocks. Rhenium is used in electrical filaments, welding rods, thermocouples, cryogenic magnets, and photographic flashbulb filaments; it is also used as a catalyst.

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« Reply #134 on: 29/01/2009 21:56:04 »
Osmium, bluish-white, brittle metallic element that has a density second only to iridium (although uncertainty has been expressed as to this and claims have been made for osmium having the highest relative density). The element is one of the transition elements of the periodic table. Osmium is not attacked by ordinary acids, but dissolves in aqua regia or fuming nitric acid. The metal occurs naturally in platinum ores and as an alloy, osmiridium, with iridium. Osmium ranks about 74th in natural abundance among the elements in crustal rock. The chief use of the metal is in the alloy osmiridium. Alloyed with platinum, it is used for standard weights and measures.

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« Reply #135 on: 29/01/2009 21:57:19 »
Iridium, white, brittle, extremely hard, metallic element. Iridium is extremely inert chemically, resisting even the action of aqua regia. In its chemical compounds it forms tetravalent and trivalent salts. It is an extremely rare metal, ranking 77th in order of abundance of the elements in the crust of the Earth. Iridium is found in alluvial deposits alloyed with platinum as platiniridium and with osmium as osmiridium. Iridium is used chiefly as an alloying material for platinum; the alloy, which contains about 10 per cent iridium, is much harder than pure platinum. Platinum-iridium alloys containing larger percentages of iridium are used in making precision instruments, surgical tools, pen points, and standard weights and lengths. Iridium was discovered by the British chemist Smithson Tennant in 1804 and was named after the iridescent nature of some of its compounds.

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« Reply #136 on: 30/01/2009 21:32:14 »
Platinum, relatively rare, chemically inert metallic element that is more valuable than gold. The element is one of the transition elements in group 10 of the periodic table. Platinum is a greyish-white metal with a hardness of 4.3. It has a high fusing point, is malleable and ductile, expands slightly upon heating, and has high electrical resistance. Chemically the metal is relatively inert and resists attack by air, water, single acids, and ordinary reagents. It dissolves slowly in aqua regia, forming chloroplatinic acid (H2PtCl6); is attacked by halogens; and combines upon ignition with sodium hydroxide, sodium nitrate, or sodium cyanide. Platinum ranks about 72nd in natural abundance among the elements in crustal rock. Except for the mineral sperrylite, which is platinum arsenide and is found only sparingly in a few localities, platinum occurs in the metallic state, often alloyed with other platinum metals. Nuggets of the metal weighing up to 9.5 kg have been found. Because of its chemical inertness and high fusing point, platinum is valuable for laboratory apparatus, such as crucibles, tongs, funnels, combustion boats, and evaporating dishes. Small amounts of iridium are usually added to increase its hardness and durability. Platinum is also used for contact points in electrical apparatus and in instruments used for measuring high temperatures. Finely divided platinum in the form of platinum sponge or platinum black is used extensively as a catalyst in the chemical industry. A considerable amount of platinum goes into jewellery, in which it is often alloyed with gold. It is also used for dental fillings.


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« Reply #137 on: 30/01/2009 21:35:14 »
Gold, Au, (from Latin aurum, “gold”), soft, dense, bright yellow metallic element. Pure gold is the most malleable and ductile of all the metals. It can easily be beaten or hammered to a thickness of 0.000013 cm, and 29 g could be drawn into a wire 100 km long. It is one of the softest metals (hardness, 2.5 to 3) and is a good conductor of heat and electricity. Finely divided gold, like other metallic powders, is black; colloidally suspended gold ranges in colour from ruby red to purple. Gold is extremely inactive. It is unaffected by air, heat, moisture, and most solvents. It will, however, dissolve in aqueous mixtures containing various halogens such as chlorides, bromides, or some iodides. It will also dissolve in some oxidizing mixtures, such as cyanide ion with oxygen, and in aqua regia, a mixture of hydrochloric and nitric acids. Gold is found in nature in quartz veins or seams, nuggets, flakes, and secondary alluvial deposits as a free metal or in a combined state. There are several chemical and physical processes that may cause these formations, and it is also likely that colonies of soil bacteria and fungi play a part in gold agglomerations. Gold is widely distributed although it is rare, being 75th in order of abundance of the elements in the crust of the Earth. It is almost always associated with varying amounts of silver; the naturally occurring gold-silver alloy is called electrum. Gold occurs, in chemical combination with tellurium, in the minerals calaverite and sylvanite along with silver, and in the mineral nagyagite along with lead, antimony, and sulphur. It occurs with mercury as gold amalgam. It is generally present to a small extent in iron pyrites; galena, the lead sulphide ore that usually contains silver, sometimes also contains appreciable amounts of gold. Gold also occurs in sea water to the extent of 5 to 250 parts by weight to 100 million parts of water. Although the quantity of gold present in sea water is more than 9 billion tonnes, the cost of recovering the gold would be far greater than the value of the gold that could thus be recovered. The major portion of the gold produced is used in coinage and jewellery. For these purposes it is alloyed with other metals to give it the necessary hardness. The gold content in alloys is expressed in carats. Coinage gold is composed of 90 parts gold to 10 parts silver. Green gold used in jewellery contains copper and silver; white gold contains zinc and nickel, or platinum metals. Gold is also used in dentistry. Radioisotopes of gold are used in biological research and in the treatment of cancer.

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« Reply #138 on: 31/01/2009 21:44:01 »
Mercury, (Latin, hydrargyrum, “liquid silver”), metallic element that is a free-flowing liquid at room temperature. Mercury, once known as liquid silver and as quicksilver, was studied in alchemy. At ordinary temperatures mercury is a shining, mobile liquid, silvery-white in colour. Slightly volatile at room temperature, mercury becomes solid when subjected to a pressure of 7,640 atmospheres (5.8 million torrs), and this pressure is used as a standard in measuring extremely high pressures. The metal dissolves in nitric or concentrated sulphuric acid but is resistant to alkalis. Mercury is acutely hazardous as a vapour and in the form of its water-soluble salts, which corrode membranes of the body. Chronic mercury poisoning, which occurs when small amounts of the metal or its fat-soluble salts, particularly methylmercury, are repeatedly ingested over long periods of time, causes irreversible brain, liver, and kidney damage. Because of increasing water pollution, significant quantities of mercury have been found in some species of fish, which has aroused concern regarding uncontrolled discharge of the metal into the environment.

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« Reply #139 on: 31/01/2009 21:46:13 »
Thallium (Greek, thallos, “young shoot”), soft, malleable metallic element that acquires a bluish-grey colour upon exposure to the atmosphere. Thallium forms a hydroxide in water, and is soluble in nitric acid and sulphuric acid. Thallous oxide, Tl2O, a black solid that, when molten, attacks glass and porcelain, is made by heating thallium in air at very high temperatures. Thallium has a high index of refraction and is therefore important in the manufacture of several types of optical glass. Thallium ranks 60th in abundance among the elements in the crust of the Earth and is a member of the aluminium family of metals. Thallium sulphate, which is odourless, tasteless, and very poisonous, is used to exterminate rodents and ants. Thallium-activated sodium iodide crystals mounted in photomultiplier tubes are used in some portable scintillation counters to detect gamma radiation. The abilities of thallium bromoiodide crystals to transmit infrared radiation and of thallium oxysulphide crystals to detect the same radiation have been employed extensively in military communication systems. Thallium alloyed with mercury forms a fluid metal that freezes at -60°C; it is used in low-temperature thermometers, relays, and switches. Thallium salts, which burn with a bright green flame, are used in rockets and flares.

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« Reply #140 on: 02/02/2009 00:33:34 »
Lead, symbol Pb (Latin, plumbum, a lead weight), dense, bluish-grey metallic element that was one of the first known metals. Metallic lead is a soft, malleable, ductile metal. When gently heated it can be forced through annular holes or dies. It has a low tensile strength and is a poor conductor of electricity. A freshly cut surface has a bright silvery lustre, which quickly turns to the dull, bluish-grey colour characteristic of the metal. Lead is used in enormous quantities in storage batteries and in sheathing electric cables. Large quantities are used in industry for lining pipes, tanks, and X-ray apparatus. Because of its high density and nuclear properties, lead is used extensively as protective shielding for radioactive material. Among numerous alloys containing a high percentage of lead are solder, type metal, and various bearing metals. A considerable amount of lead is consumed in the form of its compounds, particularly in paints and pigments. Lead is widely distributed all over the world in the form of its sulphide, the ore galena. Lead ranks about 36th in natural abundance among elements in the Earth's crust. Ores of secondary importance are cerussite and anglesite. The principal method of extracting lead from galena is to roast the ore—that is, convert it to the oxide, and reduce the oxide with coke in a blast furnace. Lead is also used in ceramic glazes and in making other pigments. In recent years, however, because of the dangers of lead poisoning, the use of lead-based paints for interior use has largely been discontinued. The so-called Dutch process is the oldest method still in use for making white lead. In this process earthenware pots containing lead gratings and ethanoic acid are wrapped in tanbark (small pieces of bark that are rich in tannin); the reaction of the fermenting tanbark and the ethanoic acid is allowed to process the lead over a period of 90 days. More rapid processes, such as electrolysis or forcing hot air and carbon dioxide through large rotating cylinders containing powdered lead and ethanoic acid, are now industrially important. Lead monoxide, or litharge (PbO), a yellow, crystalline powder formed by heating lead in air, is used in making flint glass, as a drier in oils and varnishes, and in the manufacture of insecticides. Red lead, or minium (Pb3O4), a scarlet, crystalline powder formed by oxidizing lead monoxide, is the pigment in paint used as a protective coating for structural ironwork and steelwork. Lead(II) ethanoate (Pb(C2 H3O2)2•3H2O), a white, crystalline substance called sugar of lead because of its sweet taste, is prepared commercially by dissolving litharge in ethanoic acid. It is used as a mordant in dyeing, as a paint and varnish drier, and in making other lead compounds.

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« Reply #141 on: 02/02/2009 00:35:00 »
Bismuth, rare metallic element that has a pinkish tinge. Ranking about 73rd in natural abundance among the elements in the Earth's crust, it is about as rare as silver. Most industrial bismuth is obtained as a by-product. There are several nitrates, notably bismuth nitrate, Bi(NO3)3, or bismuth trinitrate; and bismuth nitrate pentahydrate, Bi(NO3)3•5H2O. The latter form decomposes into bismuth nitrate. Bismuth nitrate is also known as bismuth oxynitrate, bismuthyl nitrate, pearl white, and Spanish white, and may be used in medicine and cosmetics. Bismuth expands on solidifying; this unusual property makes it useful for castings. Some of its alloys have unusually low melting points. One of the most strongly diamagnetic (difficult to magnetize) of all substances, bismuth tends to turn at right angles to a magnetic field. It is a poor conductor of heat and electricity, and its electrical resistance is further increased in a magnetic field; because of this property, it is used in instruments for measuring the strength of such fields. Bismuth is opaque to X-rays and can be used in fluoroscopy.

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« Reply #142 on: 02/02/2009 20:19:31 »
Polonium, rare, radioactive metallic element. Polonium is one of the elements in the uranium-radium series of radioactive decay, the first member of which is uranium-238. Polonium occurs in radium-containing ores and is found in isotopic forms with mass numbers ranging from 192 to 218. Polonium 210 (also called radium-F), the only naturally occurring isotope, has a half-life of 138 days. Because most polonium isotopes disintegrate by emitting alpha particles, the element is a good source of pure alpha radiation. It is also used in nuclear research with elements such as beryllium that emit neutrons when bombarded by alpha particles. In printing and photography equipment, polonium is used in devices that ionize the air to eliminate accumulation of electrostatic charges.

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« Reply #143 on: 02/02/2009 20:20:33 »
Astatine (Greek, astatos, “unstable”), symbol At, radioactive element that is the heaviest of the halogens. The first isotope synthesized had an atomic weight of 211 and a half-life of 7.2 hours. Subsequently, astatine-210 was produced and found to have a half-life of about 8.3 hours. Isotopes of astatine with mass numbers from 200 to 219 have been catalogued, some with half-lives measured in fractions of a second. Astatine is the halogen that behaves most like a metal and that has only radioactive isotopes. It is highly carcinogenic.

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« Reply #144 on: 03/02/2009 21:12:35 »
Radon, colourless, odourless radioactive gaseous element that is the heaviest of the noble gases of the periodic table. Radon-222, which is the most abundant isotope of radon, is formed by the radioactive decay of radium-226. Radon-222 has a half-life of 3.8 days, decaying by the emission of alpha particles into an isotope of the element polonium. Small quantities, formed by the decay of uranium minerals, are found in rock and soil, and radon makes up most normal background radioactivity. Concentrations of the gas, however, are believed to pose a serious health hazard. Radon-222 is obtained by passing air through a solution of radium salt and collecting the air and the radon gas that was present in the solution. This isotope can be used in the treatment of malignant tumours. The gas is enclosed in a tube, usually made of glass or gold, called a radon seed, which is inserted in the diseased tissue. Nineteen other isotopes of radon are known. The isotope of mass 220, discovered in 1899 by Ernest Rutherford, is a product of the radioactive decay of an isotope of thorium and is known as thoron; it has a half-life of 55 seconds. The isotope of mass 219, with a half-life of 4 seconds, is a product of the radioactive decay of an isotope of actinium and is known as actinon.

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« Reply #145 on: 03/02/2009 21:13:31 »
Francium, symbol Fr, radioactive metallic element that closely resembles caesium in chemical properties. Francium is produced when the radioactive element actinium disintegrates. Francium is naturally radioactive; its longest-lived isotope, francium-223, or actinium-K, has a half-life of 22 minutes. It emits a beta particle of 1,100,000 electronvolts (eV) energy. Isotopes ranging in mass number from 204 to 224 are known. Francium is the heaviest of the alkali metals; it is the most electropositive element. All its isotopes are radioactive and short-lived.

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« Reply #146 on: 04/02/2009 21:54:36 »
Radium (Latin, radius, “ray”), chemically reactive, silvery-white, radioactive metallic element. The element oxidizes immediately upon exposure to air. The element is used and handled in the form of radium chloride or radium bromide and practically never in the metallic state. Radium is formed by the radioactive disintegration of uranium and is consequently found in all uranium ores. Radium is present in uranium ore to the extent of one part of radium to three million of uranium. Radiation from radium has a harmful effect upon living cells, and radium burns are caused by overexposure to the rays. Cancerous cells, however, are often more sensitive to radiation than normal cells, and such cells may be killed without seriously injuring healthy tissue by controlling the intensity and direction of the radiation. Radium is now used in the treatment of only a few kinds of cancer; radium chloride or radium bromide is enclosed in a sealed tube and inserted in the diseased tissue. When a radium salt is mixed with a substance such as zinc sulphide, the substance is caused to luminesce by the bombardment of the alpha rays emitted by the radium. Small amounts of radium were once used in the production of luminous paint, which was applied to clock dials, doorknobs, and other objects, to make them glow in the dark.

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« Reply #147 on: 04/02/2009 21:56:00 »
Actinium, radioactive metallic element found in all uranium ores. The element is found in uranium ores to the extent of 2 parts to every 10 billion parts of uranium. Two naturally occurring isotopes of actinium are known. Actinium-227 is a member of the actinium series, called the actinium decay series, resulting from the radioactive decay of uranium-235. It has a half-life of 21.8 years. The other isotope, actinium-228, is a member of the thorium series resulting from the decay of thorium-232. This isotope, known also as mesothorium-2, has a half-life of 6.13 hours. Isotopes ranging in mass number from 209 to 234 are known. Actinium melts at about 1050° C, boils at about 3200° C, and has a relative density of about 10.

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« Reply #148 on: 05/02/2009 21:22:50 »
Thorium, radioactive metallic element with an atomic number of 90. The element is dark in colour, slowly attacked by water, soluble in hydrochloric and sulphuric acids, and slightly soluble in nitric acid. It ranks 39th in abundance among the elements in the crust of the Earth. Small quantities of thorium are found in thorite, or thorium silicate; in orangite, a variety of thorite; and in thorianite, a radioactive mineral composed of thorium oxide and uranium. The larger deposits occur mainly as thorium oxide, ThO2, in the monazite sands of India and Brazil. Thorium-232 occurs naturally, has a half-life of about 14 billion years, and is the first member of the radioactive-decay series, ending with the stable lead isotope lead-208. Thorium is currently important as a potential atomic-fuel source, because bombardment of thorium-232 by slow neutrons yields the fissile isotope uranium-233. This process is comparable to the process by which fast neutrons “breed” fissile plutonium-239 from non-fissile uranium-238. The thorium-uranium fuel cycle is being studied by scientists as an alternative to the uranium-plutonium fuel cycle. Two types of reactors, the molten-salt breeder reactor and the light-water breeder reactor, are being considered. Thorium metal is used in magnesium alloys and as a stabilizing component of electronic tubes. Thorium oxide is used in light filaments and electrodes and also as a catalyst.

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« Reply #149 on: 06/02/2009 22:29:47 »
Protactinium, formerly protoactinium, symbol Pa, radioactive metallic element with an atomic number of 91. It was discovered in 1918 by the Austrian-Swedish physicist Lise Meitner and the German physical chemist Otto Hahn. Protactinium is a member of the uranium-actinium radioactive-decay series and is found in uranium ores. Isotopes of protactinium ranging in mass number from 215 to 238 are known. Protactinium-233 has a half-life of 27 days. Protactinium-231, the most stable isotope, has a half-life of more than 32,000 years; by emission of an alpha particle it decays to actinium. Protactinium melts at about 1550° C, boils at about 4230° C, and has a relative density of about 15.37.