Nature of Elements
Nature of Elements
Noble Gases (2,10,18,36,54,86,118) – The noble gases are the opposite of reactive: their electron shells are full, and they do not give up any electrons without a fight. Noble gases can form compounds in a laboratory.
Semi Metals (5,14,32,33,34,51,52) – The semi metals are hard to nail down they have some properties of both metals and nonmetals. They are used in semiconductors because they are capable of conducting electricity. The conductivity can be controlled by a diode of a laser beam.
Non Metals (6-9,15-17,35,53,85,117) – The nonmetals are mostly gases. They are very reactive, have low melting points, and do not make good conductors. It can be combined to form compounds.
Alkali Metals (3,11,19,37,55,87) – The alkali metals are very reactive that single electron in their out shells is likely to jump to another atom.
Alkaline Earth Metals (4,12,20,38,56,88) – The alkaline earth metals have two electrons in their outer shells, so they are not as reactive as the alkali metals.
Transition Metals (21-30,39-48, 72,80,104-112) – The transition metals are strong hard, and shiny. They conduct electricity and heat well.
Poor Metals (13,31,49,81-84,113-116) The poor metals are soft and weak with low melting points. Poor metals are often mixed into alloys.
Lanthanide Series (58-71) – The lanthanide have so much in common that they are hard to tell apart. Samarium is a lanthanide that used to make powerful magnets.
Actinide Series (91-103) – The actinides are very radioactive elements. Some occur in nature others have been made in a laboratory.
Physics Artificial Transmutation (88-109)
Particle Accelerator (110-118)
Ninth most abundant element on Earth, it represents about 75% of all matter in the universe
Earth Atmosphere: 78% Nitrogen (N2), 20% Oxygen (O2),
.033% Carbon Dioxide (CO2) -> Ozonization (O3) 0.02-0.07 parts/million
Hydrogen,Lightest chemical element, chemical symbol H, atomic number 1. A colorless, odorless, tasteless, flammable gas, it occurs as the diatomic molecule H2. Its atom consists of one proton (the nucleus) and one electron; the isotopes deuterium and tritium have an additional one and two nuclear neutrons, respectively. Though only the ninth most abundant element on Earth, it represents about 75% of all matter in the universe. Hydrogen was formerly used to fill airships; nonflammable helium has replaced it. It is used to synthesize ammonia, ethanol, aniline, and methanol; to treat petroleum fuels; as a reducing agent (see reduction) and to supply a reducing atmosphere; to make hydrogen chloride (see hydrochloric acid) and hydrogen bromide; and in hydrogenation (e.g., of fats). Liquid hydrogen (boiling point −423 °F [−252.8 °C]) is used in scientific and commercial applications to produce extremely low temperatures and as a rocket propellant and a fuel for fuel cells. Combustion of hydrogen with oxygen gives water as the sole product. The properties of most acids, especially in water solutions, arise from the hydrogen ion (H+, also referred to as the hydronium ion, H3O+, the form in which H+ is found in a water environment). See also hydride; hydrocarbon.
It is the second most abundant and second-lightest element in the universe (after hydrogen). Helium makes up a tiny proportion of the atmosphere but as much as 7% of natural gas.
Helium, Chemical element, chemical symbol He, atomic number 2. A noble gas, it is colorless, odorless, tasteless, completely unreactive, and nontoxic. First found by spectroscopy of the Sun's atmosphere in 1868, it is the second most abundant and second-lightest element in the universe (after hydrogen). Helium makes up a tiny proportion of the atmosphere but as much as 7% of natural gas. It is the product of radioactive decay (see radioactivity) and is used in helium dating. It is used as an inert gas in welding, rocket propulsion, balloon flight, hyperbaric chambers, deep-sea diving (see nitrogen narcosis), gas chromatography, luminous signs, and cryogenics. Liquid helium, which exists only below −452 °F (−268.9 °C, about 4° C above absolute zero), is a “quantum fluid” (see fluid mechanics; quantum mechanics), with unique properties, including superfluidity, superconductivity, and near-zero viscosity.
Lightest alkali metal, It is soft, white, lustrous, and very reactive, forming compounds in which it has valence 1
Chemical element, lightest alkali metal, chemical symbol Li, atomic number 3. It is soft, white, lustrous, and very reactive, forming compounds in which it has valence 1. The metal is used in certain alloys, as a coolant in nuclear reactors, and (because of its reactivity) as a reagent, scavenger, and rocket fuel. Lithium hydride is used as a source of hydrogen; lithium hydroxide is used as an additive in storage batteries and to absorb carbon dioxide. Halides (see halogen) of lithium are used as moisture absorbents, and lithium soaps are used as thickeners in lubricating greases. Lithium carbonate is an important drug for treating depression and bipolar disorder.
It is found chiefly as the mineral beryl (of which emerald and aquamarine are gemstone varieties)
Chemical element, lightest of the alkaline earth metals, chemical symbol Be, atomic number 4. It does not occur uncombined in nature but is found chiefly as the mineral beryl (of which emerald and aquamarine are gemstone varieties). Beryllium metal, particularly in alloys, has many structural and thermal applications; it is used in nuclear reactors. Beryllium has valence 2 in all its compounds, which are generally colorless and taste distinctly sweet. All soluble beryllium compounds are toxic. Beryllium oxide is used in specialized ceramics for nuclear devices, and beryllium chloride is a catalyst for organic reactions.
Crystalline boron is a black, lustrous, very hard but brittle semiconductor, boron compounds are found widely dispersed as various minerals, including borax and the gemstone tourmaline
Semimetallic chemical element, chemical symbol B, atomic number 5. Pure crystalline boron is a black, lustrous, very hard but brittle semiconductor that does not occur naturally. Boron compounds are found widely dispersed as various minerals, including borax and the gemstone tourmaline. The element is used to harden certain steels, among other metallurgical uses, and is also used in semiconductor devices. Its borate compounds, in which it has valence 3, are essential to plant growth and have many uses in soaps, mild antiseptics, and eye ointments. Industrially, they are used as herbicides, fire retardants in fabrics, and catalysts in numerous organic chemical reactions. They are also used in electroplating and glass and ceramic formulations. The exceptional hardness and inertness of certain boron compounds, including boron carbide, aluminum boride, and boron nitride (which has an electronic structure resembling that of diamond), make them useful as abrasives and reinforcing agents, particularly for high-temperature applications.
The usual stable isotope is carbon-12; carbon-13, another stable isotope, makes up 1% of natural carbon
Earth Atmosphere: 78% Nitrogen (N2), 20% Oxygen (O2),
.033% Carbon Dioxide (CO2) -> Ozonization (O3) 0.02-0.07 parts/million
Nonmetallic chemical element, chemical symbol C, atomic number 6. The usual stable isotope is carbon-12; carbon-13, another stable isotope, makes up 1% of natural carbon. Carbon-14 is the most stable and best known of five radioactive isotopes (see radioactivity); its half-life of approximately 5,730 years makes it useful in carbon-14 dating and radio labeling of research compounds. Carbon occurs in four known allotropes: diamond, graphite, carbon black (amorphous carbon including coal, coke, and charcoal), and hollow cage molecules called fullness. Carbon forms more compounds than all other elements combined; several million carbon compounds are known. Each carbon atom forms four bonds (four single bonds, two single and one double bond, two double bonds, or one single and one triple bond) with up to four other atoms. Multitudes of chain, branched, ring, and three-dimensional structures can occur. The study of these carbon compounds and their properties and reactions is organic chemistry (see organic compound). With hydrogen, oxygen, nitrogen, and a few other elements whose small amounts belie their important roles, carbon forms the compounds that make up all living things: proteins, carbohydrates, lipids, and nucleic acids. Biochemistry is the study of how those compounds are synthesized and broken down and how they associate with each other in living organisms. Organisms consume carbon and return it to the environment in the carbon cycle. Carbon dioxide, produced when carbon is burned and from biological processes, makes up about 0.03% of the air, and carbon occurs in Earth's crust as carbonate rocks and the hydrocarbons in coal, petroleum, and natural gas. The oceans contain large amounts of dissolved carbon dioxide and carbonates.
A colorless, odorless, tasteless gas, it makes up 78% of Earth's atmosphere and is a constituent of all living matter
Gaseous chemical element, chemical symbol N, atomic number 7. A colorless, odorless, tasteless gas, it makes up 78% of Earth's atmosphere and is a constituent of all living matter. As the nearly unreactive diatomic molecule N2, it is useful as an inert atmosphere or to dilute other gases. Nitrogen is commercially produced by distillation of liquefied air. Nitrogen fixation, achieved naturally by soil microbes and industrially by the Haber-Bosch process, converts it to water-soluble compounds (including ammonia and nitrates). Industrially, ammonia is the starting material for most other nitrogen compounds (especially nitrates and nitrites), whose main uses are in agricultural fertilizers and explosives. In compounds, nitrogen usually has valence 3 or 5. It forms several oxides including nitrous oxide (N2O; laughing gas), nitric oxide (NO), nitrogen dioxide (NO2), and other forms (such as N2O3 and N2O5). Some of the nitrogen oxides, often referred to generically as NOx, are notorious as contributors to urban air pollution. Other compounds include the nitrites, exceptionally hard materials made from nitrogen and a metal; cyanides; azides, used in detonators and percussion caps; and thousands of organic compounds containing nitrogen in functional groups or in a linear or ring structure (see hetero-cyclic compound). See also nitrogen cycle.
Earth Atmosphere: 78% Nitrogen (N2), 20% Oxygen (O2),
.033% Carbon Dioxide (CO2) -> Ozonization (O3) 0.02-0.07 parts/million
Gaseous chemical element, chemical symbol O, atomic number 8. It constitutes 21% (by volume) of air and more than 46% (by weight) of Earth's crust, where it is the most plentiful element. It is a colorless, odorless, tasteless gas, occurring as the diatomic molecule O2. In respiration, it is taken up by animals and some bacteria (and by plants in the dark), which give off carbon dioxide (CO2). In photosynthesis, green plants assimilate carbon dioxide in the presence of sunlight and give off oxygen. The small amount of oxygen that dissolves in water is essential for the respiration of fish and other aquatic life. Oxygen takes part in combustion and in corrosion but does not itself burn. It has valence 2 in compounds; the most important is water. It forms oxides and is part of many other molecules and functional groups, including nitrate, sulfate, phosphate, and carbonate; alcohols, aldehydes, carboxylic acids, and ketones; and peroxides. Obtained for industrial use by distillation of liquefied air, oxygen is used in steel-making and other metallurgical processes and in the chemical industry. Medical uses include respiratory therapy, incubators, and inhaled anesthetics. Oxygen is part of all gas mixtures for manned spacecraft, scuba divers, workers in closed environments, and hyperbaric chambers. It is also used in rocket engines as an oxidizer (in liquefied form) and in water and waste treatment processes.
Its chief source is fluorite; it also occurs in cryolite, fluorapatite, seawater, bones, and teeth.
Sodium Floride (0.25%)
Anticavity, Antigingivitis, Stengthens Enamel
Nonmetallic chemical element, chemical symbol F, atomic number 9. The lightest halogen, it is the most reactive element, forming compounds with all others except helium, neon, and argon (the lighter noble gases). Its only valence is 1, in F2 (the diatomic molecule) and fluorides. A toxic, pale yellow gas with a pungent odor, it can be produced only by electrolysis under special conditions. Its chief source is fluorite; it also occurs in cryolite, fluorapatite, seawater, bones, and teeth. Hydrogen fluoride (HF) is a raw material for many other fluorides. Its water solution, hydrofluoric acid, is used to clean metals and to polish, etch, or frost glass. Other fluorides are useful catalysts and raw materials. Sodium fluoride (NaF) is added to water and tin fluoride (SnF2) to dental-care products to reduce dental caries (see fluoridation of water). Fluorocarbons are hydrocarbons in which some hydrogen atoms have been replaced by fluorine atoms; examples include Freons and Teflon.
Chemical element, chemical symbol Ne, atomic number 10. One of the noble gases, neon is colorless, odorless, tasteless, and completely unreactive. It occurs in minute amounts in the atmosphere and is obtained by fractional distillation of liquefied air. When under low pressure, it glows a bright orange-red if an electric current is passed through it. It was discovered in 1898, and since the 1920s its chief use has been in luminous tubes and bulbs.
The sixth most abundant element on Earth, it occurs mainly as halite
Its sodium salt is the food, used as a flavor enhancer, and salt water helps gill function.
Chemical element, one of the alkali metals, chemical symbol Na, atomic number 11. A very soft, silvery white metal, the sixth most abundant element on Earth, it occurs mainly as halite, never free. Extremely reactive, it is used as a chemical reagent and raw material, in metallurgy, as a heat exchanger (in nuclear power generators and certain types of engines), and in sodium-vapor lamps (see electric discharge lamp). Sodium is essential for life but rarely deficient in diets; high intake is linked to hypertension. Sodium in compounds, many of great industrial importance (including bicarbonate of soda, caustic soda, sodium nitrate [Chile saltpeter], and sodium chloride), has valence 1. Sodium carbonate, one of the four most important basic chemical commodities, is used in making glass, detergents, and cleansers. Sodium hypochlorite, familiar as household bleach, is also used to bleach paper pulp and textiles, to chlorinate water, and in some medicines. The sulfate is used in the craft process and also used to make paperboard, glass, and detergents. The thiosulfate (hyposulfite, or “hypo”) is used to developed photographs.
Manganese is essential to plants for growth and to higher animals to promote the action of many enzymes.
Do not exceed 10 mg daily
400 mcg (20%)
Chemical element, one of the alkaline earth metals, chemical symbol Mg, atomic number 12. The silvery white metal does not occur free in nature, but compounds such as the sulfate (Epsom salts), oxide (magnesia), and carbonate (magnesite) have long been known. The metal, which burns in air with a bright white light, is used in photographic flash devices, bombs, flares, and pyrotechnics; it is also a component of lightweight alloys for aircraft, spacecraft, cars, machinery, and tools. The compounds, in which it has valence 2, are used as insulators and refractories and in fertilizers, cement, rubber, plastics, foods, and pharmaceuticals (antacids, purgatives, laxatives). Magnesium is an essential element in human nutrition; it is the co factor in enzymes of carbohydrate metabolism and in chlorophyll.
A lightweight, silvery white metal, it is so reactive chemically that it always occurs in compounds. It is the most abundant metallic element in Earth's crust, chiefly in bauxite (its principal ore), feldspars, micas, clay minerals, and laterite. It also occurs in gemstones, such as topaz, garnet, and chrysoberyl; emery, corundum, ruby, and sapphire are crystalline aluminum oxide.
Uses: Aluminum Foil
Metallic chemical element, chemical symbol Al, atomic number 13. A lightweight, silvery white metal, it is so reactive chemically that it always occurs in compounds. It is the most abundant metallic element in Earth's crust, chiefly in bauxite (its principal ore), feldspars, micas, clay minerals, and laterite. It also occurs in gemstones, such as topaz, garnet, and chrysoberyl; emery, corundum, ruby, and sapphire are crystalline aluminum oxide. Aluminum was first isolated in 1825, became commercially available in the late 19th century, and is now the most widely used metal after iron. Its surface oxidizes at once to a hard, tough film, deterring further corrosion. Uses include building and construction, corrosion-resistant chemical equipment, auto and aircraft parts, power transmission lines, photoengraving plates, cookware and other consumer goods, and tubes for ointments and pastes. Important compounds include alums; alumina (aluminum oxide), useful as corundum and as a carrier for many catalysts; aluminum chloride, a widely used catalyst for organic syntheses; and aluminum hydroxide, used to waterproof fabrics.
Second only to oxygen in abundance in Earth's crust, it never occurs free but is found in almost all rocks and in sand, clay, and soils, combined with oxygen as silica (silicon dioxide, SiO2) or with oxygen and metals as silicate minerals. It occurs in many plants and some animals.
Uses: Electronic circuits and switching devices, including computer chips, transistors, and diodes.
Nonmetallic to semimetallic chemical element, chemical symbol Si, atomic number 14. Second only to oxygen in abundance in Earth's crust, it never occurs free but is found in almost all rocks and in sand, clay, and soils, combined with oxygen as silica (silicon dioxide, SiO2) or with oxygen and metals as silicate minerals. It occurs in many plants and some animals. Pure silicon is a hard, dark gray solid with a metallic lustre and the same crystal structure as diamond. It is an extremely important semiconductor; doped (see dopant) with boron, phosphorus, or arsenic, it is used in various electronic circuit and switching devices, including computer chips, transistors, and diodes. Silicon is also used in metallurgy as a reducing (see reduction) agent and in steel, brass, and bronze. Its usual valence in compounds is 4. Silica is used in the form of sand and clay for many purposes; as quartz, it may be heated to form special glasses. Silicates are used in making glass, enamels, and ceramics; sodium silicates (water glass) are used in soaps, wood treatment, cements, and dyeing. See also silane; silicone.
Nonmetallic chemical element, chemical symbol P, atomic number 15. The ordinary allotrope, called white phosphorus, is a poisonous, colorless, semitransparent, soft, waxy solid that glows in the dark
Nonmetallic chemical element, chemical symbol P, atomic number 15. The ordinary allotrope, called white phosphorus, is a poisonous, colorless, semitransparent, soft, waxy solid that glows in the dark (see phosphorescence) and combusts spontaneously in air, producing dense white fumes of the oxide P4O10; it is used as a rodenticide and a military smokescreen. Heat or sunlight converts it to the red phosphorus allotrope, a violet-red powder that does not phosphorescence or ignite spontaneously. Much less reactive and soluble than white phosphorus, it is used in manufacturing other phosphorus compounds and in semiconductors, fertilizers, safety matches, and fireworks. Black phosphorus, made by heating the white form under pressure, is flaky like graphite. Phosphorus seldom occurs uncombined in nature. As the phosphate ion, it is abundant and widely distributed, in apatite, phosphorite, and many other minerals. Phosphorus has valence 3 or 5 in compounds, which have many uses in industry. Phosphine (PH3) is a chemical raw material and a doping agent (deliberately added impurity) for solid-state electronics components. Organic phosphorus compounds are used as plasticizers, gasoline additives, insecticides (e.g., parathion), and nerve gases. In living organisms the role of phosphorus is essential; it is a component of DNA and RNA, ATP, and bone.
Nonmetallic chemical element, chemical symbol S, atomic number 16. Sulfur crystals from Sicily (greatly enlarged). It is very reactive but occurs native in deposits, as well as combined in various ores (e.g., pyrite, galena, cinnabar); in coal, petroleum, and natural gas; and in the water in sulfur springs. Sulfur is the third most abundant constituent of minerals and one of the four most important basic chemical commodities.
Uses: amino acids, the sulfa drugs, and many insecticides, solvents, and substances used in making rubber and rayon.
Nonmetallic chemical element, chemical symbol S, atomic number 16. Sulfur crystals from Sicily (greatly enlarged). It is very reactive but occurs native in deposits, as well as combined in various ores (e.g., pyrite, galena, cinnabar); in coal, petroleum, and natural gas; and in the water in sulfur springs. Sulfur is the third most abundant constituent of minerals and one of the four most important basic chemical commodities. Pure sulfur, a tasteless, odorless, brittle yellow solid, occurs in several crystalline and amorphous allotropes, including brimstone and flowers of sulfur. It combines, with valence 2, 4, or 6, with nearly all other elements. Its most familiar compound is hydrogen sulfide, a poisonous gas that smells like rotten eggs. All metals except gold and platinum form sulfides, and many ores are sulfides. The oxides are sulfur dioxide and sulfur trioxide, which when dissolved in water make sulfurous acid and sulfuric acid, respectively. Several sulfur compounds with halogen elements are industrially important. Sodium sulfite (Na2SO3) is a reducing agent used to pulp paper and in photography. Organic compounds with sulfur include several amino acids, the sulfa drugs, and many insecticides, solvents, and substances used in making rubber and rayon.
Nonmetallic chemical element, chemical symbol Cl, atomic number 17. It is a toxic, corrosive, greenish yellow gas (as the diatomic molecule Cl2) that severely irritates the eyes and respiratory system (and was used for that purpose as a chemical-warfare agent in World War I). As the chloride ion and in the hypochlorite ion, it has valence 1; in the chlorite, chlorate, and perchlorate ions, it has higher valences. Chlorine and its compounds are important industrial materials with myriad uses in the manufacture of other chlorinated compounds (e.g., PVC, hydrochloric acid, ethylene dichloride, trichloroethylene, PCBs), in water purification (municipal systems, swimming pools), in textile industries, in flame retardants, in special batteries, and in food processing. Sodium chloride (table salt) is by far the most familiar of its compounds. See also bleach.
Chemical element, chemical symbol Ar, atomic number 18. Colorless, odorless, and tasteless, it is the most abundant of the noble gases on Earth and the one most used in industry. It constitutes about 1% of air and is obtained by distillation of liquid air. Argon provides an inert gas shield in welding and brazing, in light bulbs and lasers, in Geiger counters, and in the production and fabrication of certain metals. Because a radioactive form of argon is produced by decay of a naturally occurring radioactive potassium isotope, it can be used to date rocks and samples more than 100,000 years old.
Potassium is essential for life and is present in all soils. Potassium ions (K+) and sodium ions act at cell membranes in electrochemical impulse transmission and in transport.
60 mg (1.4%)
Chemical element, one of the alkali metals, chemical symbol K, atomic number 19. It is a soft, silvery white metal, not found free in nature and rarely used as the metal (except as a chemical reagent) because of its extreme reactivity. Potassium is essential for life and is present in all soils. Potassium ions (K+) and sodium ions act at cell membranes in electrochemical impulse transmission and in transport. Potassium in compounds has valence 1. The chloride is used as a fertilizer and a raw material for producing other compounds, and the hydroxide for making liquid soaps and detergents and in preparing various salts. The iodide is added to table salt to protect against iodine deficiency. The nitrate is also called saltpeter, and the carbonate is called potash.
Do not exceed 2,500 mg daily
Chemical element, one of the alkaline earth metals, chemical symbol Ca, atomic number 20. The most abundant metallic element in the human body, it is an essential part of bones and teeth and has many physiological functions (see calcium deficiency; tooth). It is the fifth most abundant element in Earth's crust but does not occur naturally in the free state. In its compounds calcium has valence 2. It occurs in limestone, chalk, marble, dolomite, eggshells, pearls, coral, and many marine shells as calcium carbonate, or calcite; in apatite as calcium phosphate; in gypsum as calcium sulfate; and in many other minerals. It is used as an alloying agent and in other metallurgical applications; its alloy with lead is used in cable sheathing and grids for batteries. Calcite is used as a lime source, a filler, a neutralizer, and an extender; in pure form it is used in baking powder and as an antacid and calcium supplement. Calcium oxide (lime) and its product after water addition, calcium hydroxide (slaked lime), are important industrially. Other significant compounds are calcium chloride (a drying agent), calcium hypochlorite (a bleach), calcium sulfate (gypsum and plaster of Paris), and calcium phosphate (a plant food and stabilizer for plastics).
Sc45 occurs naturally
A chemical element, Sc, atomic number 12, and atomic weight 44.965. it is the first transtion element of the first long period. Some physical properties of scandium are listed in the table. Isotopes of scandium include Sc40 and Sc51 and one corresponding to every intermediate value. Except for Sc45, which occur naturally, the isotope occur when generated artificially.
Metallic chemical element, one of the transition elements, chemical symbol Ti, atomic number 22. A silvery gray, lightweight, high-strength, low-corrosion structural metal, it is found combined in almost all rocks and soils and in plants and animals, natural waters, and deep-sea dredging.
Metallic chemical element, one of the transition elements, chemical symbol Ti, atomic number 22. A silvery gray, lightweight, high-strength, low-corrosion structural metal, it is found combined in almost all rocks and soils and in plants and animals, natural waters, and deep-sea dredging. Its chief commercial ores are ilmenite and rutile. Its alloys are used for parts for high-speed aircraft, spacecraft, missiles, and ships; in electrodes; in chemical, desalination, and food-handling equipment; and in prostheses. Its compounds, in which it has valence 2, 3, or 4, include titanium trichloride (used as a catalyst in polypropylene production), titanium dioxide (extensively used as a pigment—with the greatest hiding power of all white pigments—in paints, enamels, and lacquers), and titanium tetrachloride (used in skywriting, smoke screens, and as a catalyst).
Metallic chemical element, one of the transition elements, chemical symbol V, atomic number 23. A silvery white, soft metal found (always combined) in various minerals, coal, and petroleum, it is used in alloys with steel and iron for high-speed tool steel, high-strength low-alloy steel, and wear-resistant cast iron. Unalloyed, it is used in high-temperature applications, as a target in X-ray applications, and as a catalyst. Its compounds, in which it has various valences, have many beautiful colors in solution and are used as catalysts and mordants (see dye).
Metallic chemical element, one of the transition elements, chemical symbol Cr, atomic number 24. A hard, steel-gray metal that takes a high polish, it is used in alloys (e.g., ferrochromium, steel, stainless steel) to increase strength and corrosion resistance. It usually has valence 2, 3, or 6 and always occurs combined with other elements, especially oxygen; chromite is its only commercial source. Various colored gemstones (e.g., ruby, emerald, serpentine) owe their color to chromium. Sodium chromate and dichromate are used in leather tanning, in metal surface treatment, and as catalysts. Chromium trioxide is used in chrome plating and as a colorant for ceramics. Chromium oxide, lead chromate, and various other chromium compounds are used as pigments. Chromium dioxide, strongly magnetic, is used in recording tapes and as a catalyst.
Metallic chemical element, one of the transition elements, chemical symbol Mn, atomic number 25. It is a silvery white, hard, brittle metal, widely distributed in Earth's crust in combination with other elements. Nodules rich in manganese occur in huge quantities on the seafloor, but no economical way to mine them has been devised. More than 95% of the manganese produced is used in iron and steel alloys and much of the rest in nonferrous aluminum and magnesium alloys to improve their corrosion resistance and mechanical properties. Manganese compounds, in which it has various valences, are used in fertilizers and textile printing and as reagents and raw materials. Potassium permanganate is used for disinfecting, deodorizing, and bleaching and as a reagent in analysis. Manganese is essential to plants for growth and to higher animals to promote the action of many enzymes.
Metallic chemical element, one of the transition elements, chemical symbol Fe, atomic number 26. Iron is the most used and cheapest metal, the second most abundant metal and fourth most abundant element in Earth's crust. It occurs rarely as a free metal, occasionally in natural alloys (especially in meteorites), and in hundreds of minerals and ores, including hematite, magnetite, limonite, and siderite. The human body contains about one-sixth of an ounce (4.5 g) of iron, mostly in hemoglobin and its precursors; iron in the diet is essential to health. Iron is ferromagnetic (see ferromagnetism) at ordinary temperatures and is the only metal that can be tempered (see tempering). Its uses in steels of various types, as well as in cast and wrought iron (collectively, “ferrous metals”), are numerous. Alteration of its properties by impurities, especially carbon, is the basis of steel making. Iron in compounds usually has valence 2 (ferrous) or 3 (ferric). Ferrous and ferric oxides (FeO and Fe2O3, respectively) are used as pigments and the latter as jewelers' rouge. Rust is ferric oxide containing water; ferric oxide is widely used as a magnetic recording material in computer data-storage devices and magnetic tapes. Ferrous and ferric sulfates and chlorides are all of industrial importance as mordants, reducing agents, flocculating agents, or raw materials and in inks and fertilizers.
Metallic chemical element, one of the transition elements, chemical symbol Co, atomic number 27. Widely dispersed in small amounts in many minerals and ores, this magnetic, silvery white metal with a faint bluish tinge is used mostly for special alloys (e.g., alnico, tool steel) with exacting applications. At valence 2 or 3 it forms numerous coordination complexes. One is vitamin B12 (cyanocobalamin; see vitamin B complex). Cobalt and its compounds are used in electroplating and coloring ceramics and glass and as lamp filaments, catalysts, a trace element in fertilizers, and paint and varnish driers. The pigment cobalt blue has a variable composition, roughly that of cobalt oxide plus alumina. A radioactive isotope of cobalt emits penetrating gamma rays that are used in radiation therapy.
Metallic chemical element, one of the transition elements, chemical symbol Ni, atomic number 28. Nickel is silvery white, tough, harder than iron, ferromagnetic (see ferromagnetism), and highly resistant to rusting and corrosion. It occasionally occurs free and is fairly common but not often concentrated in igneous rocks. As pure metal, it is used to coat other metals (see plating) and as a catalyst. In alloys, it is used in coins, Monel metal, nickel silver, nickel-chrome and stainless steels, permanant magnets, and cutlery. Its compounds, in which it most often has valence 2, have a variety of industrial uses, as catalysts and mordants (see dye) and in electroplating.
Metallic chemical element, one of the transition elements, chemical symbol Cu, atomic number 29. Crystalline copper from Michigan, Sometimes found in the free state in nature, it is a reddish metal, very ductile and an unusually good conductor of electricity and heat. Most of the world's copper production is used by the electrical industries; the remainder is combined with other metals (e.g., zinc, tin, nickel) to form alloys such as brass, bronze, nickel silver, and Monel. Copper is part of nearly all coinage metals. In compounds copper usually has valence 1 (cuprous) or 2 (cupric). Cuprous compounds include cuprous oxide, a red pigment and a fungicide; cuprous chloride, a catalyst for certain organic reactions; and cuprous sulfide, with a variety of uses. Cupric compounds include cupric oxide, a pigment, decolorizing agent, and catalyst; cupric chloride, a catalyst, wood preservative, mordant, disinfectant, feed additive, and pigment; and cupric sulfate, a pesticide, germicide, feed additive, and soil additive. Copper is a necessary trace element in the human diet and essential to plant growth; in blue-blooded mollusks and crustaceans it plays the same role in hemocyanin as iron does in hemoglobin.
Metallic chemical element, chemical symbol Zn, atomic number 30. Zinc is a bluish silver metal, ductile when very pure but brittle otherwise. It forms brass (with copper) and many other alloys. Its major use is in galvanizing iron, steel, and other metals. Zinc is an essential trace element, particularly in red blood cells; in snails, it corresponds to iron in the blood of vertebrates. Zinc oxide is used as a pigment, ultraviolet light absorber (to prevent sunburn), dietary supplement and seed treatment, and photoconductor. Zinc's many other compounds (in which it has valence 2 or, rarely, 1) are used in industrial and consumer applications, including as pesticides, pigments, mordants (see dye), fluxes, and wood preservatives.
Metallic chemical element, chemical symbol Ga, atomic number 31. Silvery white and soft enough to be cut with a knife, gallium has an unusually low melting point (about 30 °C [86 °F]), which allows it to liquefy in the palm of the hand. The liquid metal clings to or wets glass and similar surfaces. Gallium expands on solidification and super cools readily, remaining liquid at temperatures as low as 0 °C (32 °F). In various combinations with aluminum, indium, phosphorus, arsenic, and antimony, it forms compounds (e.g., gallium arsenide and indium gallium arsenide phosphide) with valuable semiconductor and opto-electronic properties; some of these compounds form the basis for such electronic devices as light-emitting diodes and semiconductor lasers.
Semimetallic chemical element, chemical symbol Ge, atomic number 32. Germanium, which resembles silicon in its physical properties, is used especially in semiconductor devices. Discovered in 1886, it became economically significant after 1945 and remains of primary importance in the manufacture of transistors and of components for other devices such as rectifiers (see diode) and photocells. It is also used as a component of alloys, in phosphors for fluorescent lamps, and in the glasses of certain optical components, such as camera and microscope lenses.
Nonmetallic to semimetallic chemical element, chemical symbol As, atomic number 33. Arsenic (gray) with regular (red) and orpiment (yellow),It exists uncombined in two stable (and several unstable) allotropes, one gray and one yellow, but is more often found in nature as the sulfide or oxide. The elemental form is used to form alloys of metals (especially lead), and certain semiconductors are made from crystals of gallium arsenide (GaAs). Arsenious oxide (arsenic trioxide or white arsenic, As2O3) is used in pesticides, as a pigment, and as a preservative of hides and wood; this is the poisonous “arsenic” (see arsenic poisoning) in detective stories. Arsenic pentoxide (As2O5) is also used in insecticides, herbicides, metal adhesives, and pigments.
Semimetallic chemical element, chemical symbol Se, atomic number 34. It is widely distributed, usually in small amounts, occasionally uncombined but more often as selenides of iron, lead, silver, or copper. Selenium has several allotropes; the gray metallic crystalline form is the most stable at room temperature. Its electrical conductivity increases when light strikes it, and it can convert light directly into electricity, so selenium is used in photocells (e.g., in light meters and security alarms), solar cells, and photocopiers. It also has been used in rectifiers to convert alternating to direct electric current. It serves as a red colorant for glass and glazes. Selenium has valence 2, 4, and 6 in its compounds, many of which are toxic though the element is not. Selenium dioxide is an important reagent in organic chemistry. Vital to living cells, it works as an antioxidant in the body and is being studied for a variety of possible beneficial health effects; it is used in nutritional supplements and animal feeds.
Nonmetallic chemical element, chemical symbol Br, atomic number 35. One of the halogens, it is a deep red, fuming liquid at ordinary temperatures (freezing point 19 °F [−7.2 °C]; boiling point 138 °F [59 °C]) that contains diatomic molecules (Br2), and it does not occur free in nature. It is obtained from seawater and brines or salt beds. Extremely irritating and toxic, bromine is a strong oxidizing agent (see oxidation-reduction). Its compounds, in which it may have valence 1, 3, 5, or 7, have many uses, including as petroleum additives (ethylene dibromide), in photographic emulsions (silver bromide), as sedatives, and in flour (potassium bromate).
Chemical element, chemical symbol Kr, atomic number 36. One of the noble gases, it is colorless, odorless, tasteless, and almost totally inert, combining only with fluorine under very rigorous conditions. Krypton occurs in trace amounts in the atmosphere and in rocks and is obtained by fractional distillation of liquefied air. It is used in luminescent tubes, flash lamps, incandescent light bulbs, lasers, and tracer studies.
Method of estimating the age of rocks, minerals, and meteorites from measurements of the amount of the stable isotope strontium-87 formed by the decay of the unstable isotope rubidium-87 that was present in the rock at the time of its formation. The method is applicable to very old rocks because the transformation is extremely slow: the half-life, or time required for half the initial quantity of rubidium-87 to disappear, is approximately 48.8 billion years. See also dating.
Chemical element, one of the alkaline earth metals, chemical symbol Sr, atomic number 38. A soft metal, it has a silvery lustre when freshly cut but reacts rapidly with air. In both the metal and the compounds (in which it has valence 2), strontium resembles calcium and barium so closely that it has few uses that the other two elements cannot supply more cheaply. The nitrate and chlorate, very volatile, give off brilliant crimson flames and are used in flares, fireworks, and tracer bullets. The radioactive isotope strontium-90 (see radioactivity), produced in nuclear explosions, is the principal health hazard in fallout; it can replace some of the calcium in foods, concentrate in bones and teeth, and cause radiation injury.
A chemical element, Y, atomic number 39, and atomic weight 88.905. Yttrium resembles the rare earth elements closely. The stable isotope Y89 constitutes 100% of the natural element, which is always found associated with the rare earths is frequently classified as on. Yttrium metal absorbs hydrogen, and in alloys up to a composition of YH2 they remble metals very closely. In fact, in certain composition ranges, the alloy is a better conductor of electricity than the pure metal. Yttrium forms the matric for the europium activated yttrium phospohors which emit a brillant, clear-red light when excited by electrons. The television industry uses these phosphors in manufacturing television screens. Yttrium is used commercially in the metal industry for ally purposes and a getter to remove oxygen and nonmetallic impurities in other metals. For properties of the metal and its salts.
Metallic chemical element, one of the transition elements, chemical symbol Zr, atomic number 40. The metal is hard and brittle when impure, soft and ductile when highly purified. It is relatively abundant, occurring as zircon (also marketed as a natural gemstone) and baddeleyite. Highly transparent to neutrons, zirconium became important in the 1940s in nuclear energy applications such as fuel cladding. Other uses are in alloys, fireworks, and flashbulbs and as a scavenger for oxygen and other gases. Its compounds, in most of which it has valence 4, are important industrial materials. Zirconia (the oxide) is used in piezoelectric crystals (see piezoelectricity), high-frequency induction coils, colored glazes and glasses, and heat-resistant fibers; zirconium carbonate is employed in preparations to treat the rash of poison ivy.
A chemical elemnt, Nb, atomic number 41 atomic weight 92.906. In the United States this elements was originally called columbium. The metallurgist and metals industry still use this older name. Most niobium is used in special stainless steels, high temperature alloys, and superconducting alloys such as Nb3Sn. Niobium is also used in nuclear piles. Niobium metal has a density 8.6 g/cm3 (5.0 oz/in) at 20 degrees, a melting point of 2468 degrees Celsius and a boiling point of 4927 C. Metallic niobium is quite inert to all acids except hydrofluoric, presumably owing to an exide film on the surface. Niobium metal is slowly oxidized in alkaline solution. It reacts with oxygen and the halogens upon heating to form the oxidation state V oxide and halides, with nitrogen to form NbN, and with carbon to form NbC, as well as other elements such as arsenic, antimony, tellurium, and selenium. The oxide Nb2O5, melting point 1520 degrees, dissolves in fused alkali to yield a soluble complex niobate, Nb6019. Normal niobates such as NbO4 are insoluble. The oxide dissolves in hyrdofluoric acid to give ionic species such as NbOF5 and NbOF6, depending on the fluride and hydrogen ion concentration. The highest fluoro complex which can exist in a solution is NbF6.
Metallic chemical element, one of the transition elements, chemical symbol Mo, atomic number 42. It is a silvery gray, relatively rare metal with a high melting point (4,730 °F [2,610 °C]) that does not occur uncombined in nature. Since molybdenum and its alloys have useful strength at temperatures that melt most other metals and alloys, they are used in high-temperature steels. Applications include reaction vessels; aircraft, missile, and automobile parts; and electrodes, heating elements, and filament supports. Some molybdenum compounds (in which it has various valences) are used as pigments and catalysts. Molybdenum disulfide is a solid lubricant, used alone or added to greases and oils.
Metallic chemical element, one of the transition elements, chemical symbol Tc, atomic number 43. All its isotopes are radioactive (see radioactivity); some occur in trace amounts in nature as nuclear fission products of uranium. Its isotope technetium-97 was the first element artificially produced (1937; see cyclotron). Technetium-99, a fission product of nuclear reactors that emits gamma rays, is the most-used tracer isotope in nuclear medicine. Technetium resembles platinum in appearance and manganese and rhenium in chemical behavior. It is also used as a metallurgical tracer and in corrosion-resistant products.
A chemical element, Ru, is atomic number 44, and atomic weight 101.07. Rutheium is a hard white metal, workable only at high temperatures and then only with difficulty. Ruthenium is an excellent catalyst, useful in reactions involving hydrogenation, isomerization, oxidation, and reforming. Use of pure ruthenium metal are minor. Ruthenium is an effective harderner for platinum and palladium. Alloys with large percentages (30-70%) of ruthenium containing other precious or base metals have been used for electrical contacts and applications, where extreme wear resistance and corrosion pivots. Ruthenium is restant to the common acids, including aqua regia, at temperatures up to 100 C and upt o 300 C in case of sulfuric acid. It also resists hyrdofluoric and phosphoric acids at 100 C. Posttsium ruthenate, KruO2H20, is soluble in water and is useful in purifying ruthenium. Ruthenium trichloride, RuCl3, is soluble in water but decomposes in hot water.
Metallic chemical element, one of the transition elements, chemical symbol Rh, atomic number 45. Chemically related to platinum, it is a precious, silver-white metal mainly used as an alloying agent for the latter element. Rhodium added to platinum in small amounts yields alloys that are harder and that lose mass at high temperatures more slowly than pure platinum. Such alloys are used for laboratory furnace crucibles, spark-plug electrodes, catalysts in very hot chemical environments (including automobile catalytic converters), and high-temperature thermocouples. Because rhodium resists tarnishing at ordinary temperatures and is highly reflective, it is in demand as a surface electroplating for jewelry and other decorative articles. The plated metal is also used for reflecting surfaces in optical instruments.
Metallic chemical element, one of the transition elements, chemical symbol Pd, atomic number 46. A precious, silver-white metal that resembles platinum chemically, it is extremely ductile and easily worked and can be beaten into thin leaf. It is an excellent catalyst for chemical reactions involving hydrogen and oxygen, such as the hydrogenation of unsaturated organic compounds. Because it does not tarnish in air at ordinary temperatures, palladium and its alloys serve as substitutes for platinum in jewelry and in electrical contacts in telecommunications equipment. Small amounts of palladium alloyed with gold yield the best white gold. Palladium is used also in dental alloys. Because hydrogen passes rapidly through the metal at high temperatures, heated palladium tubes impervious to other gases function as semipermeable membranes and are used for hydrogen purification.
Metallic chemical element, one of the transition elements, chemical symbol Ag, atomic number 47. Dendritic (branching) silver from Ontario. It is a white, lustrous precious metal, valued for its beauty. It is also valued for its electrical conductivity, which is the highest of any metal. Between copper and gold in their common group of the periodic table, it is intermediate between them in many properties. Widely distributed in nature in small amounts, as the native metal and in ores, it is usually recovered as a by-product of copper and lead production. Its use in bullion and coins was overtaken in the 1960s by demand for industrial purposes, especially photography. It is also used in printed electrical circuits, electronic conductors, and contacts. It is the catalyst for converting ethylene to ethylene oxide, the precursor of many organic chemicals. Its use in alloys in sterling (92.5% silver, 7.5% copper) and plated silverware, ornaments, and jewelry remains important; yellow gold used in jewelry is typically 25% silver, and gold dental alloys are about 10% silver. Silver dental fillings are an amalgam of silver and mercury. Silver in compounds, the most important of which is silver nitrate, has valence 1. Its chloride, bromide, and iodide are used in photography and its iodide in cloud seeding.
Metallic chemical element, chemical symbol Cd, atomic number 48. It normally occurs along with other metals, especially zinc, in ores. A silvery white metal capable of taking a high polish, cadmium does not corrode under alkaline (see alkali) conditions; one of its major uses is in electroplating other metals and alloys to protect them. Because it absorbs neutrons effectively, it is used in control rods in some nuclear reactors. Its compounds, in which it has valence 2, are very toxic. They are used as pigments, as phosphors in television and computer monitor screens, as pesticides, and in photographic applications and analytical chemistry.
Metallic chemical element, chemical symbol In, atomic number 49. Of a brilliant, silvery-white lustre, it is so soft that it can be scratched with a fingernail. Its most common isotope, indium-115, is very weakly radioactive, with a half-life measured in billions of years. Like tin, the pure metal emits a high-pitched “cry” when bent, and, like gallium, molten indium wets glass and other surfaces, which makes it valuable for producing seals between glass, metals, quartz, ceramics, and marble. The metal is used in coating high-performance engine bearings and is an ingredient in low-melting-point alloys for sprinkler heads, fire-door links, and fusible plugs. In various combinations with elements such as gallium, phosphorus, and arsenic, it forms compounds having semiconductor properties useful in electronics, including solid-state light-emitting devices. Transparent electrodes made from an oxide of indium and tin are widely employed in liquid crystal displays.
Metallic chemical element, chemical symbol Sn, atomic number 50. It is a soft, silvery white metal with a bluish tinge, employed since antiquity in the traditional form of bronze, its alloy with copper. It occurs chiefly as the dioxide (stannic oxide, SnO2) in cassiterite. Since it is nontoxic, ductile, malleable, and easily worked, it is used to plate steel cans (“tin cans”) for use as food containers and to coat and plate other items. Pure tin is too weak to be used alone, but its many alloys include soft solder, pewter, bronze, and low-temperature casting alloys. It has valence 2 or 4 in compounds, including stannous chloride (used in tin galvanizing and manufacturing polymers and dyes), stannous oxide (used to make tin salts for chemical reagents and plating), stannous fluoride (used as an anti-cavity ingredient in toothpastes), stannic chloride (a stabilizer for perfumes and a source of other tin salts), and stannic oxide (a catalyst and a polishing powder for steel). Tin bonds with carbon to form organotin compounds, used to stabilize PVC and in biocides and fungicides.
Semimetallic to metallic chemical element (see metal), chemical symbol Sb, atomic number 51. Of its various allotropes, the most common is a lustrous, bluish, brittle, flaky solid. In nature antimony occurs chiefly as the gray sulfide mineral stibnite, Sb2S3. Pure antimony metal has no important uses, but its alloys and compounds are extremely useful. Some antimony alloys have the rare quality of expanding on solidifying; these are used for castings and for type metal. Alloys with lead are used in car batteries, bullets, and cable sheaths. Antifriction alloys with tin and lead (Babbitt metals) are used as components of machine bearings. Antimony compounds (valences 3, 4, and 5) are widely used as flame retardants in paints, plastics, rubber, and textiles; others are used as paint pigments.
Eight stable isotopes of natural tellurium
A chemical element, Te, atomic nubmer 52, and chemical atomic weight 127.60. There are eight stable isotopes of natural tellurium. Tellurium makes up approximately 10^90 of the Earth's igneous rock. It is found as the free element, sometimes, associated iwth selenium. It is more often found as the telluride sylvanite (graphics tellurium), nagyagite (black tellurium), hessite, tetradymite, altaite, coloradoite, and other silver-gold, tellurides, as well as the oxide, tellurium ocher. There are two important allotropic modifications of elemental tellurium , the crystalline and the amorphous forms. The crystalline form has a silver white color and metallic appearnce. This form melts at 841.6 F and boils at 2543 F. It has a specific gravity of 6.25 and a hardness of 2.5 on Mohs scale. The amorphous form (brown) has a specific gravity of 6.015. Telluriuum burns in air with blue flame, forming, tellurium, dioxide, TeO2. It reacts with halogens, but not sulfur or selenium, and forms, among other products, both the dinegative telluride anion (Te2), which resembles selenide, and the tetrapositive tellurium cation (Te4) which resembles platinum (IV). Tellurium is used primarily as an additive to steel to increase it ductility, as a brightener in electroplating baths, as an additive to catalyst for the cracking of petroleum, as a coloring material for glasses, and as an additive to lead to increase its strenth and corrosiun resistance.
Nonmetallic chemical element, chemical symbol I, atomic number 53. The heaviest nonradioactive halogen, it is a nearly black crystalline solid (diatomic molecule I2) that sublimes (see sublimation) to a deep violet, irritating vapor. It is never found in nature uncombined. Its sources (mostly in brines and seaweeds) and compounds are usually iodides; iodates (small amounts in saltpeter) and periodates also occur. Dietary iodine is essential for thyroid gland function; in areas of the world where food contains insufficient iodine, an iodine compound such as potassium iodide (KI) is added to table salt (sodium chloride) to prevent iodine deficiency. Elemental iodine is used in medicine, in synthesizing some organic chemicals, in manufacturing dyes, in analytical chemistry (see analysis) to measure fat saturation (see hydrogenation) and to detect starch, and in photography. The radioactive isotope iodine-131 (see radioactivity), with an eight-day half-life, is very useful in medicine (see nuclear medicine) and other applications.
Chemical element, chemical symbol Xe, atomic number 54. One of the noble gases, it is colorless, odorless, tasteless, and nearly inert, combining only with fluorine and oxygen and in complexes (see bonding). Xenon occurs in slight traces in Earth's atmosphere and in rocks. Obtained by fractional distillation of liquefied air, it is used in luminescent tubes (see electric discharge lamp), flash lamps, lasers, and tracer studies and as an anesthetic.
Chemical element, one of the alkali metals, chemical symbol Cs, atomic number 55. The first element discovered by spectroscopy (1860), it is silvery white, liquid at warm room temperature (melting at 83 °F [28.4 °C]), and very soft when solid. About half as abundant as lead, it occurs in minute quantities as ores. It reacts explosively with cold water and is used to scavenge traces of oxygen and other gases in electron tubes. Other uses are as a catalyst and in photoelectric cells, ion propulsion systems, atomic clocks, and plasma for thermoelectric conversion. Cesium salts have various specialty applications, including in mineral waters.
Chemical element, one of the alkaline earth metals, chemical symbol Ba, atomic number 56. It is very reactive and in compounds always has valence 2. In nature it is found chiefly as the minerals barite (barium sulfate) and withe rite (barium carbonate). The element is used in metallurgy, and its compounds are used in fireworks, petroleum mining, and radiology and as pigments and reagents. All soluble barium compounds are toxic. Barium sulfate, one of the most insoluble salts known, is given in a “barium meal” as a contrast medium for X-ray examination of the gastrointestinal tract.
Any of the series of 15 consecutive chemical elements in the periodic table from lanthanum to lutetium (atomic numbers 57–71). With scandium and yttrium, they make up the rare earth metals. Their atoms have similar configurations and similar physical and chemical behavior; the most common valences are 3 and 4.
Chemical element, a rare earth metal of the lanthanide series (hence having many properties of the transition elements), chemical symbol Ce, atomic number 58. It is iron-gray and fairly soft and ductile. Found in many ores, it is about as abundant as copper and three times as abundant as lead. The metal is used in alloys and other metallurgical applications and (because it oxidizes strongly and rapidly) in illumination, ignition, and signaling devices and in propellants. Misch metal, used in lighter flints, is 50% cerium. Cerium compounds (in which it has valence 3 or 4) are used in the mantles of lanterns, in the ceramic, photographic, and textile industries, and in analytical chemistry.
Glass containing a mixture of neodymium and praseodymium (another rare earth element) is used in glassblowers' goggles.
Metallic chemical element, chemical symbol Nd, atomic number 60. Silvery white in color, it is a rare earth metal and one of the lanthanide series. It is a component of important alloys, among them misch metal (15% neodymium), used in lighter flints and various metallurgical processes. Alloyed with iron and boron, neodymium is the basis for powerful permanent magnets used in computer hard drives, lightweight earphones, and numerous other applications. Neodymium compounds are employed as ceramics glazes. The crude oxide counteracts the greenish cast imparted to glass by iron contaminants, and a very pure oxide is used to make a vivid purple glass. Neodymium is added to glass or other host materials to form the active elements for certain solid-state lasers. Glass containing a mixture of neodymium and praseodymium (another rare earth element) is used in glassblowers' goggles.
It is produced artifically from uranium, thorium, and plutonium.
A chemical element, Pm, atomic number 61. Promehtium is the missing element of the lanthanide and rare earth series. The atomic weight of the most abundant separated radioisotope is 147. Although a number of scientists have claimed to have discovered this element in nature as a result of obersving certain spectral lines, no one has succeeded in isolating element 61 from naturally occurring materials.
7 naturally occuring isotopes
A chemical element, Sm, atomic number 62, belonging to a rare earth group Its atomic weight is 150.35, and there are 7 naturally occuring isotopes, Sm147, Sm148, and Sm149 are radioactive and emits particles. Samarium oxide is a pale yellow, is readily soluble in most acids, and give topaz yellow salts in solutions. Samarium has round rather limited use in the ceramic industry, and it is used has a very high cross section for the capture of neutrons, and therfore there has been some interest in samrium.
A chemical element, Eu, atomic number 63, atomic weight 151.96, a member of the rare earth group. The stable isotopes, Eu151 and Eu153, make up the naturally occurring element. The metal is the second most volatile of the rare earth and has a considerable vapor pressure at its melting point. It is very soft is rapidly attacked by air, and really bleongs more to the calcium strontium barium series than to the rare earth series. The television industry uses considerable quantities of phospors, such as europium activated ytrrium phosphors have been patented. These phosphors give a brillant red color and are used in the manufacture of television screens.
A chemical element, Yb, atomic number 70, and atomic weight 173.04. Ytterbium is a metal element of the rare earth group. There are 7 naturally occuring stable isotopes. The common oxide, Yb203, is a colorless and dissolves readily in acids to form colorless solutions of trivalent salts which are paramagnetic. Ytterbium also forms a series of divalent compounds. The divalent salts are soluble in water but react very slowly with water to libertate hydrogen. The metal is best prepared by distillation. It is a silver soft metal which corrodes slowly in air and rembles the calcium strontium barium series more than the rare earth series. For a discussion of the properties of the betal and its salts
Metallic chemical element, one of the transition elements, chemical symbol Ta, atomic number 73. It is a dense, hard, unreactive, silvery gray metal with an extremely high melting point (5,425 °F [2,996 °C]). Relatively rare, it occurs native in a few places. It is difficult to separate from niobium, the element above it in the periodic table, with which it shares many properties. The most important uses are in electrolytic capacitors, corrosion-resistant chemical equipment, dental and surgical instruments, tools, catalysts, components of electron tubes, rectifiers, and prostheses. Its compounds are relatively unimportant commercially; tantalum carbide is used in machine tools and dies.
Metallic chemical element, one of the transition elements, chemical symbol Ir, atomic number 77. A very rare, precious, silvery white, hard, brittle metal that resists most acids, it is one of the densest substances known on Earth. It probably does not occur uncombined in nature but is found in natural alloys with other noble (i.e., chemically inactive or inert) metals. The pure metal is too hard to work with to have any significant uses; alloys with platinum are used in jewelry, pen points, surgical pins and pivots, electrical contacts and sparking points, and extrusion dies. The international prototype kilogram, the primary standard (see weights and measures) for weight, is made of an alloy comprising 90% platinum and 10% iridium. The discovery of abnormally high amounts of iridium in rocks dating to the boundary between the Cretaceous and Tertiary periods led to a much-debated hypothesis that an iridium-containing asteroid striking Earth led to a catastrophic chain of events including the extinction of dinosaurs and many other forms of life.
Metallic chemical element, one of the transition elements, chemical symbol Pt, atomic number 78. A very heavy, silvery white precious metal, it is soft and ductile, with a high melting point (3,216 °F [1,769 °C]) and good resistance to corrosion and chemical attack. Small amounts of iridium are commonly added for a harder, stronger alloy that retains platinum's advantages. Platinum is found usually as alloys of 80–90% purity in placer deposits or more rarely combined with arsenic or sulfur. It is indispensable in high-temperature laboratory work for electrodes, dishes, and electrical contacts that resist chemical attack even when very hot. Platinum is used in dental alloys and surgical pins; alloys typically containing 90–95% platinum are used in expensive jewelry. The international primary standard for the kilogram is made of 90% platinum, 10% iridium. Platinum has valence 2 or 4 in its compounds, which include many coordination complexes. It and some compounds are useful catalysts, particularly for hydrogenation and in catalytic converters for reducing automobile emissions.
Metallic chemical element, one of the transition elements, chemical symbol Au, atomic number 79. It is a dense, lustrous, yellow, malleable precious metal, so durable that it is virtually indestructible, often found uncombined in nature. Jewelry and other decorative objects have been crafted from gold for thousands of years. It has been used for coins, to back paper currencies, and as a reserve asset. Gold is widely distributed in all igneous rocks, usually pure but in low concentrations; its recovery from ores and deposits has been a major preoccupation since ancient times (see cyanide process). The world's gold supply has seen three great leaps, with Christopher Columbus's arrival in the Americas in 1492, with discoveries in California (see gold rush) and Australia (1850–75), and discoveries in Alaska, Yukon (see Klondike), and South Africa (1890–1915). Pure gold is too soft for prolonged handling; it is usually used in alloys with silver, copper, and other metals. In addition to being used in jewelry and as currency, gold is used in electrical contacts and circuits, as a reflective layer in space applications and on building windows, and in filling and replacing teeth. Dental alloys are about 75% gold, 10% silver. In jewelry, its purity is expressed in 24ths, or karats: 24-karat is pure, 12-karat is 50% gold, etc. Its compounds, in which it has valence 1 or 3, are used mainly in plating and other decorative processes; a soluble chloride compound has been used to treat rheumatoid arthritis.
Metallic chemical element, chemical symbol Hg, atomic number 80. Mercury is the only elemental metal that is liquid at ordinary temperatures, with a freezing point of −38 °F (−39 °C) and a boiling point of 674 °F (356.9 °C). Silvery white, dense, toxic (see mercury poisoning), and a good conductor of electricity, mercury is occasionally found free in nature but usually occurs as the red sulfide ore, cinnabar (HgS). It has many uses—in dental and industrial amalgams, as a catalyst, in electrical and measuring apparatus and instruments (e.g., thermometers), as the cathode in electrolytic cells, in mercury-vapour lamps, and as a coolant and neutron absorber in nuclear power plants. Many of mercury's compounds, in which it has valence 1 or 2, are pigments, pesticides, and medicinals. It is a dangerous pollutant because it concentrates in animal tissues in increasing amounts up the food chain.
Metallic chemical element, chemical symbol Pb, atomic number 82. Lead is a soft, silvery white or grayish, malleable, ductile, dense metal that conducts electricity poorly. Its stable isotopes are all end products of radioactive decay of uranium and other heavy elements. Known since ancient times, lead is so durable and resistant to corrosion that Roman lead pipes are still usable. Lead is used in roofing, as cable coverings, and in pipes, conduits, and structures. Other uses are in storage batteries, ammunition, and low-melting-point alloys (e.g., solder, pewter) and as shielding against sound, vibrations, and radiation. Lead is rarely found free in nature; its major ore is the sulfide galena (PbS). Because it and its compounds are poisons (see lead poisoning), lead-based paints and gasoline additives have been phased out in many countries. Lead in compounds has valence 2 and 4; an oxide (litharge, PbO) is the most widely used. Lead compounds are added to lead crystal (see glass), glazes, and ceramics and are used as pigments, drying agents for paints and varnishes, insecticides and herbicides, and fireproofing agents and in matches, explosives, and pyrotechnics. Almost half of all lead is recovered from recycled scrap. The “lead” in pencils is graphite.
Semimetallic to metallic chemical element, chemical symbol Bi, atomic number 83. Hard, brittle, and lustrous, it has a distinctive gray-white color with a reddish tinge. It is often found free in nature and also occurs in compounds and in mixed ores. Bismuth alloys are used (because of their low melting points) in making metal castings, special solders, automatic sprinkler heads, fuses, and many fire-detection devices. Bismuth phosphomolybdate is a catalyst in the production of acrylonitrile, an important raw material for fibres and plastics. Salts of bismuth are used in making soothing agents for digestive disorders (especially bismuth subsalicylate), in treating skin infections and injuries, and in lipstick, nail polish, and eye shadow, to which they impart a pearlescent quality.
Chemical element, chemical symbol Rn, atomic number 86. The heaviest noble gas, it is colorless, odorless, tasteless, radioactive (see radioactivity), and almost completely unreactive (forming compounds only with fluorine). It is rare in nature because all its isotopes are short-lived and because radium, its source, is scarce. Radon seeps from certain soils and rocks (such as granite) into the atmosphere and can accumulate in poorly ventilated spaces near ground level, including house basements; in some regions of the world the use of such spaces is believed to increase the risk of lung cancer more than any other common factor except smoking. Radon is used in radiotherapy, radiography, and research.
Chemical element, heaviest alkaline earth metal, chemical symbol Ra, atomic number 88. It was discovered by Marie Curie and her husband, Pierre Curie, in 1898 and isolated by 1910. All its isotopes are radioactive (see radioactivity). Radium does not occur free in nature but occurs in natural ores such as pitchblende as a disintegration product of radioactive decay of heavier elements, including uranium. Chemically it is highly reactive and has valence 2 in all of its compounds. Its use in medicine (see radiation therapy; radiology; nuclear medicine) has declined because of its cost, and its use in consumer goods (to illuminate watch and clock hands and numbers, as well as instrument dials) was halted because it can cause radiation injury. It is still used for some radiography and as a source of neutrons.
Metallic chemical element, chemical symbol Th, atomic number 90. One of the actinide series of elements, natural thorium is a mixture of radioactive isotopes, predominantly thorium-232 (half-life of more than 10 billion years). It is a dense metal that is silver-white in pure form but turns gray or black on prolonged exposure to air. Although not a nuclear reactor fuel itself, thorium-232 can be used in breeder reactors because, on capturing slow-moving neutrons, it decays into fissionable uranium-233. Thorium is added to magnesium and its alloys to improve their high-temperature strength. Added to glass, it yields glasses with a high refractive index, useful for specialized optical applications. It was formerly in great demand as a component of mantles for gas and kerosene lamps and has been used in the manufacture of tungsten filaments for light bulbs and vacuum tubes.
Chemical element of the actinide series (with many transition element properties), chemical symbol U, atomic number 92. A dense, hard, silvery white metal that tarnishes in air, it is isolated from such ores as pitchblende. Until the discovery of the first trans uranium element in 1940, uranium was believed to be the heaviest element. Radioactivity was discovered in uranium by A.-H. Becquerel. All its isotopes are radioactive; several have half-lives long enough to permit determination of the age of the Earth by uranium-thorium-lead dating and uranium-234–uranium-238 dating. Nuclear fission was discovered in 1938 in uranium bombarded with neutrons, and the self-sustaining nuclear chain reaction, the atomic bomb, and the generation of nuclear power followed. Uranium has various valences in compounds, some of which have been used as colors in ceramic glazes, in light bulb filaments, in photography, and as dyes and mordants.
Radioactive (see radioactivity) metallic chemical element, chemical symbol Pu, atomic number 94. A member of the actinide series of transition elements, it is the most important transuranium element because of its use in certain types of nuclear reactors (see nuclear power) and in nuclear weapons. It is found in nature only in traces produced by natural neutron irradiation in uranium ores. It is produced artificially by neutron irradiation of uranium-238. Plutonium is a silvery metal that tarnishes in air; it is warm because of energy released in alpha decay. Its isotopes, all radioactive, are highly toxic radiological poisons (see radiation injury) because they give off alpha particles and are specifically absorbed by bone marrow.
Synthetic radioactive chemical element, chemical symbol Am, atomic number 95. The fourth transuranium element discovered, it was first produced in 1944 from plutonium-239 in a nuclear reactor. The isotope americium-241 has been prepared in kilogram quantities and is used in a variety of measuring applications that utilize its gamma radiation. Its most familiar use is in household smoke detectors.