Sinonimi di Chemical elements
hydrogenH1a flammable colourless gas that is the lightest and most abundant element in the universe. It occurs mainly in water and in most organic compounds and is used in the production of ammonia and other chemicals, in the hydrogenation of fats and oils, and in welding. Symbol: H; atomic no: 1; atomic wt: 1.00794; valency: 1; density: 0.08988 kg/m3; melting pt: –259.34°C; boiling pt: –252.87°C heliumHe2lithiumLi3berylliumBe4boronB5carbonC6nitrogenN7a colourless odourless relatively unreactive gaseous element that forms 78 per cent (by volume) of the air, occurs in many compounds, and is an essential constituent of proteins and nucleic acids: used in the manufacture of ammonia and other chemicals and as a refrigerant. Symbol: N; atomic no: 7; atomic wt: 14.00674; valency: 3 or 5; density: kg/m3; melting pt: –210.00°C; boiling pt: –195.8°C oxygenO8fluorineF9a toxic pungent pale yellow gas of the halogen group that is the most electronegative and reactive of all the elements, occurring principally in fluorspar and cryolite: used in the production of uranium, fluorocarbons, and other chemicals. Symbol: F; atomic no: 9; atomic wt: 18.9984032; valency: 1; density: 1.696 kg/m3; relative density: 1.108; freezing pt: –219.62°C; boiling pt: –188.13°C neonNe10sodiumNa11a very reactive soft silvery-white element of the alkali metal group occurring principally in common salt, Chile saltpetre, and cryolite. Sodium and potassium ions maintain the essential electrolytic balance in living cells. It is used in the production of chemicals, in metallurgy, and, alloyed with potassium, as a cooling medium in nuclear reactors. Symbol: Na; atomic no: 11; atomic wt: 22.989768; valency: 1; relative density: 0.971; melting pt: 97.81±0.03°C; boiling pt: 892.9°C magnesiumMg12aluminium or (U.S.) aluminumAl13a silvery, lightweight, easily worked, metallic chemical element that resists corrosion and is found abundantly, but only in combination: symbol, Al; at. no., 13 siliconSi14phosphorusP15sulphur or (U.S.) sulfurS16a pale-yellow, nonmetallic chemical element found in crystalline or amorphous form: it burns with a blue flame and a stifling odor and is used in vulcanizing rubber and in making matches, paper, gunpowder, insecticides, sulfuric acid, etc.: symbol, S; at. no., 16 chlorineCl17a toxic pungent greenish-yellow gas of the halogen group; the 15th most abundant element in the earth's crust, occurring only in the combined state, mainly in common salt: used in the manufacture of many organic chemicals, in water purification, and as a disinfectant and bleaching agent. Symbol: Cl; atomic no: 17; atomic wt: 35.4527; valency: 1, 3, 5, or 7; density: 3.214 kg/m3; relative density: 1.56; melting pt: –101.03°C; boiling pt: –33.9°C argonAr18potassiumK19a light silvery element of the alkali metal group that is highly reactive and rapidly oxidizes in air; occurs principally in carnallite and sylvite. It is used when alloyed with sodium as a cooling medium in nuclear reactors and its compounds are widely used, esp in fertilizers. Symbol: K; atomic no: 19; atomic wt: 39.0983; valency: 1; relative density: 0.862; melting pt: 63.71°C; boiling pt: 759°C calciumCa20scandiumSc21titaniumTi22vanadiumV23chromiumCr24manganeseMn25ironFe26cobaltCo27nickelNi28copperCu29zincZn30a brittle bluish-white metallic element that becomes coated with a corrosion-resistant layer in moist air and occurs chiefly in sphalerite and smithsonite. It is a constituent of several alloys, esp brass and nickel-silver, and is used in die-casting, galvanizing metals, and in battery electrodes. Symbol: Zn; atomic no: 30; atomic wt: 65.39; valency: 2; relative density: 7.133; melting pt: 419.58°C; boiling pt: 907°C galliumGa31germaniumGe32a brittle crystalline grey element that is a semiconducting metalloid, occurring principally in zinc ores and argyrodite: used in transistors, as a catalyst, and to strengthen and harden alloys. Symbol: Ge; atomic no: 32; atomic wt: 72.61; valency: 2 or 4; relative density: 5.323; melting pt: 938.35°C; boiling pt: 2834°C arsenicAs33a toxic metalloid element, existing in several allotropic forms, that occurs principally in realgar and orpiment and as the free element. It is used in transistors, lead-based alloys, and high-temperature brasses. Symbol: As; atomic no: 33; atomic wt: 74.92159; valency: –3, 0, +3, or +5; relative density: 5.73 (grey); melting pt: 817°C at a pressure of 3MN/m2 (grey); sublimes at 613°C (grey) seleniumSe34bromineBr35a pungent dark red volatile liquid element of the halogen series that occurs in natural brine and is used in the production of chemicals, esp ethylene dibromide. Symbol: Br; atomic no: 35; atomic wt: 79.904; valency: 1, 3, 5, or 7; relative density 3.12; density (gas): 7.59 kg/m3; melting pt: –7.2°C; boiling pt: 58.78°C kryptonKr36rubidiumRb37strontiumSr38yttriumY39zirconiumZr40a greyish-white metallic element, occurring chiefly in zircon, that is exceptionally corrosion-resistant and has low neutron absorption. It is used as a coating in nuclear and chemical plants, as a deoxidizer in steel, and alloyed with niobium in superconductive magnets. Symbol: Zr; atomic no: 40; atomic wt: 91.224; valency: 2, 3, or 4; relative density: 6.506; melting pt: 1855±2°C; boiling pt: 4409°C niobiumNb41molybdenumMo42technetiumTc43a silvery-grey metallic element, artificially produced by bombardment of molybdenum by deuterons: used to inhibit corrosion in steel. The radioisotope technetium-99m, with a half-life of six hours, is used in radiotherapy. Symbol: Tc; atomic no: 43; half-life of most stable isotope, 97Tc: 2.6 × 106 years; valency: 0, 2, 4, 5, 6, or 7; relative density: 11.50 (calculated); melting pt: 2204°C; boiling pt: 4265°C rutheniumRu44a hard brittle white element of the platinum metal group. It occurs free with other platinum metals in pentlandite and other ores and is used to harden platinum and palladium. Symbol: Ru; atomic no: 44; atomic wt: 101.07; valency: 0–8; relative density: 12.41; melting pt: 2334°C; boiling pt: 4150°C rhodiumRh45a hard corrosion-resistant silvery-white element of the platinum metal group, occurring free with other platinum metals in alluvial deposits and in nickel ores. It is used as an alloying agent to harden platinum and palladium. Symbol: Rh; atomic no: 45; atomic wt: 102.90550; valency: 2–6; relative density: 12.41; melting pt: 1963±3°C; boiling pt: 3697±100°C palladiumPd46a ductile malleable silvery-white element of the platinum metal group occurring principally in nickel-bearing ores: used as a hydrogenation catalyst and, alloyed with gold, in jewellery. Symbol: Pd; atomic no: 46; atomic wt: 106.42; valency: 2, 3, or 4; relative density: 1202; melting pt: 1555°C; boiling pt: 2964°C silverAg47a very ductile malleable brilliant greyish-white element having the highest electrical and thermal conductivity of any metal. It occurs free and in argentite and other ores: used in jewellery, tableware, coinage, electrical contacts, and in electroplating. Its compounds are used in photography. Symbol: Ag; atomic no: 47; atomic wt: 107.8682; valency: 1 or 2; relative density: 10.50; melting pt: 961.93°C; boiling pt: 2163°C cadmiumCd48a malleable ductile toxic bluish-white metallic element that occurs in association with zinc ores. It is used in electroplating, alloys, and as a neutron absorber in the control of nuclear fission. Symbol: Cd; atomic no: 48; atomic wt: 112.411; valency: 2; relative density: 8.65; melting pt: 321.1°C; boiling pt: 767°C indiumIn49a rare soft silvery metallic element associated with zinc ores: used in alloys, electronics, and electroplating. Symbol: In; atomic no: 49; atomic wt: 114.82; valency: 1, 2, or 3; relative density: 7.31; melting pt: 156.63°C; boiling pt: 2073°C tinSn50a metallic element, occurring in cassiterite, that has several allotropes; the ordinary malleable silvery-white metal slowly changes below 13.2°C to a grey powder. It is used extensively in alloys, esp bronze and pewter, and as a noncorroding coating for steel. Symbol: Sn; atomic no: 50; atomic wt: 118.710; valency: 2 or 4; relative density: 5.75 (grey), 7.31 (white); melting pt: 231.9°C; boiling pt: 2603°C antimonySb51telluriumTe52a brittle silvery-white nonmetallic element occurring both uncombined and in combination with metals: used in alloys of lead and copper and as a semiconductor. Symbol: Te; atomic no: 52; atomic wt: 127.60; valency: 2, 4, or 6; relative density: 6.24; melting pt: 449.57±0.3°C; boiling pt: 988°C iodineI53xenonXe54a colourless odourless gaseous element occurring in trace amounts in air; formerly considered inert it is now known to form compounds and is used in radio valves, stroboscopic and bactericidal lamps, and bubble chambers. Symbol: Xe; atomic no: 54; atomic wt: 131.29; valency: 0; density: 5.887 kg/m3; melting pt: –111.76°C; boiling pt: –108.0°C caesium or (U.S.) cesiumCs55a soft, silver-white, ductile, metallic chemical element, one of the alkali metals and the most electropositive of all the elements: it ignites in air, reacts vigorously with water, and is used in photoelectric cells: symbol, Cs; at. no., 55: a radioactive isotope (cesium-137) with a half-life of 30.17 years is a fission product and is used in cancer research, radiation therapy, etc. bariumBa56lanthanumLa57ceriumCe58praseodymiumPr59a malleable ductile silvery-white element of the lanthanide series of metals. It occurs principally in monazite and bastnaesite and is used with other rare earths in carbon-arc lights and as a pigment in glass. Symbol: Pr; atomic no: 59; atomic wt: 140.90765; valency: 3; relative density: 6.773; melting pt: 931°C; boiling pt: 3520°C neodymiumNd60promethiumPm61a radioactive element of the lanthanide series artificially produced by the fission of uranium. Symbol: Pm; atomic no: 61; half-life of most stable isotope, 145Pm: 17.7 years; valency: 3; melting pt: 1042°C; boiling pt: 2460°C (approx.) samariumSm62a silvery metallic element of the lanthanide series occurring chiefly in monazite and bastnaesite and used in carbon-arc lighting, as a doping agent in laser crystals, and as a neutron-absorber. Symbol: Sm; atomic no: 62; atomic wt: 150.36; valency: 2 or 3; relative density: 7.520; melting pt: 1074°C; boiling pt: 1794°C europiumEu63gadoliniumGd64terbiumTb65dysprosiumDy66holmiumHo67a malleable silver-white metallic element of the lanthanide series. Symbol: Ho; atomic no: 67; atomic wt: 164.93032; valency: 3; relative density: 8.795; melting pt: 1474°C; boiling pt: 2700°C erbiumEr68thuliumTm69ytterbiumYb70lutetium or luteciumLu71hafniumHf72a bright metallic element found in zirconium ores: used in tungsten filaments and as a neutron absorber in nuclear reactors. Symbol: Hf; atomic no: 72; atomic wt: 178.49; valency: 4; relative density: 13.31; melting pt: 2231±20°C; boiling pt: 4603°C tantalumTa73a hard greyish-white metallic element that occurs with niobium in tantalite and columbite: used in electrical capacitors in most circuit boards and in alloys to increase hardness and chemical resistance, esp in surgical instruments. Symbol: Ta; atomic no: 73; atomic wt: 180.9479; valency: 2, 3, 4, or 5; relative density: 16.654; melting pt: 3020°C; boiling pt: 5458±100°C tungstenW74rheniumRe75a dense silvery-white metallic element that has a high melting point. It occurs principally in gadolinite and molybdenite and is used, alloyed with tungsten or molybdenum, in high-temperature thermocouples. Symbol: Re; atomic no: 75; atomic wt: 186.207; valency: –1 or 1–7; relative density: 21.02; melting pt: 3186°C; boiling pt: 5596°C (est) osmiumOs76a very hard brittle bluish-white metal occurring with platinum and alloyed with iridium in osmiridium: used to produce platinum alloys, mainly for pen tips and instrument pivots, as a catalyst, and in electric-light filaments. Symbol: Os; atomic no: 76; atomic wt: 190.2; valency: 0 to 8; relative density: 22.57; melting pt: 3033±30°C; boiling pt: 5012±100°C iridiumIr77a very hard inert yellowish-white transition element that is the most corrosion-resistant metal known. It occurs in platinum ores and is used as an alloy with platinum. Symbol: Ir; atomic no: 77; atomic wt: 192.22; valency: 3 or 4; relative density: 22.42; melting pt: 2447°C; boiling pt: 4428°C platinumPt78a ductile malleable silvery-white metallic element, very resistant to heat and chemicals. It occurs free and in association with other platinum metals, esp in osmiridium: used in jewellery, laboratory apparatus, electrical contacts, dentistry, electroplating, and as a catalyst. Symbol: Pt; atomic no: 78; atomic wt: 195.08; valency: 1–4; relative density: 21.45; melting pt: 1769°C; boiling pt: 3827±100°C goldAu79mercuryHg80thalliumTl81leadPb82bismuthBi83poloniumPo84a very rare radioactive element that occurs in trace amounts in uranium ores. The isotope polonium-210 is produced artificially and is used as a lightweight power source in satellites and to eliminate static electricity in certain industries. Symbol: Po; atomic no: 84; half-life of most stable isotope, 209Po: 103 years; valency: –2, 0, 2, 4, or 6; relative density (alpha modification): 9.32; melting pt: 254°C; boiling pt: 962°C astatineAt85a radioactive element of the halogen series: a decay product of uranium and thorium that occurs naturally in minute amounts and is artificially produced by bombarding bismuth with alpha particles. Symbol: At; atomic no: 85; half-life of most stable isotope, 210At: 8.1 hours; probable valency: 1,3,5, or 7; melting pt: 302°C; boiling pt: 337°C (est) radonRn86a colourless radioactive element of the rare gas group, the most stable isotope of which, radon-222, is a decay product of radium. It is used as an alpha particle source in radiotherapy. Symbol: Rn; atomic no: 86; half-life of 222Rn: 3.82 days; valency: 0; density: 9.73 kg/m3; melting pt: –71°C; boiling pt: –61.7°C franciumFr87an unstable radioactive element of the alkali-metal group, occurring in minute amounts in uranium ores. Symbol: Fr; atomic no: 87; half-life of most stable isotope, 223Fr: 22 minutes; valency: 1; melting pt: 27°C; boiling pt: 677°C radiumRa88a highly radioactive luminescent white element of the alkaline earth group of metals. It occurs in pitchblende, carnotite, and other uranium ores, and is used in radiotherapy and in luminous paints. Symbol: Ra; atomic no: 88; half-life of most stable isotope, 226Ra: 1620 years; valency: 2; relative density: 5; melting pt: 700°C; boiling pt: 1140°C actiniumAc89a radioactive element of the actinide series, occurring as a decay product of uranium. It is used as an alpha-particle source and in neutron production. Symbol: Ac; atomic no: 89; half-life of most stable isotope,227Ac: 21.6 years; relative density: 10.07; melting pt: 1051°C; boiling pt: 3200 ± 300°C thoriumTh90a soft ductile silvery-white metallic element. It is radioactive and occurs in thorite and monazite: used in gas mantles, magnesium alloys, electronic equipment, and as a nuclear power source. Symbol: Th; atomic no: 90; atomic wt: 232.0381; half-life of most stable isotope, 232Th: 1.41 × 1010 years; valency: 4; relative density: 11.72; melting pt: 1755°C; boiling pt: 4788°C protactiniumPa91a toxic radioactive metallic element that occurs in uranium ores and is produced by neutron irradiation of thorium. Symbol: Pa; atomic no: 91; half-life of the most stable isotope, 231Pa: 32 500 years; valency: 4 or 5; relative density: 15.37 (calc.); melting pt: 1572°C uraniumU92neptuniumNp93a silvery metallic transuranic element synthesized in the production of plutonium and occurring in trace amounts in uranium ores. Symbol: Np; atomic no: 93; half-life of most stable isotope, 237Np: 2.14 × 106 years; valency: 3, 4, 5, or 6; relative density: 20.25; melting pt: 639±1°C; boiling pt: 3902°C (est) plutoniumPu94a highly toxic metallic transuranic element. It occurs in trace amounts in uranium ores and is produced in a nuclear reactor by neutron bombardment of uranium-238. The most stable and important isotope, plutonium-239, readily undergoes fission and is used as a reactor fuel in nuclear power stations and in nuclear weapons. Symbol: Pu; atomic no: 94; half-life of 239Pu: 24 360 years; valency: 3, 4, 5, or 6; relative density (alpha modification): 19.84; melting pt: 640°C; boiling pt: 3230°C americiumAm95a white metallic transuranic element artificially produced from plutonium. It is used as an alpha-particle source. Symbol: Am; atomic no: 95; half-life of most stable isotope, 243Am: 7.4 × 103 years; valency: 2,3,4,5, or 6; relative density: 13.67; melting pt: 1176°C; boiling pt: 2607°C (est) curiumCm96a silvery-white metallic transuranic element artificially produced from plutonium. Symbol: Cm; atomic no: 96; half-life of most stable isotope, 247Cm: 1.6 x 107 years; valency: 3 and 4; relative density: 13.51 (calculated); melting pt: 1345±400°C berkeliumBk97a metallic transuranic element produced by bombardment of americium. Symbol: Bk; atomic no: 97; half-life of most stable isotope, 247Bk: 1400 years; valency: 3 or 4; relative density: 14 (est) californiumCf98a metallic transuranic element artificially produced from curium. Symbol: Cf; atomic no: 98; half-life of most stable isotope, 251Cf: 800 years (approx.) einsteiniumEs99a metallic transuranic element artificially produced from plutonium. Symbol: Es; atomic no: 99; half-life of most stable isotope, 252Es: 276 days fermiumFm100a transuranic element artificially produced by neutron bombardment of plutonium. Symbol: Fm; atomic no: 100; half-life of most stable isotope, 257Fm: 80 days (approx.) mendeleviumMd101a transuranic element artificially produced by bombardment of einsteinium. Symbol: Md; atomic no: 101; half-life of most stable isotope, 258Md: 60 days (approx.); valency: 2 or 3 nobeliumNo102a transuranic element produced artificially from curium. Symbol: No; atomic no: 102; half-life of most stable isotope, 255No: 180 seconds (approx.); valency: 2 or 3 lawrenciumLr103a transuranic element artificially produced from californium. Symbol: Lr; atomic no: 103; half-life of most stable isotope, 256Lr: 35 seconds; valency: 3 rutherfordiumRf104a transactinide element produced by bombarding californium-249 nuclei with carbon-12 nuclei. Symbol: Rf; atomic number.: 104; atomic wt: 261 dubniumDb105a synthetic transactinide element produced in minute quantities by bombarding plutonium with high-energy neon ions. Symbol: Du; atomic no 105 seaborgiumSg106a synthetic transuranic element, synthesized and identified in 1974. Symbol: Sg; atomic no: 106 bohriumBh107a transuranic element artificially produced in minute quantities by bombarding 204Bi atoms with 54Cr nuclei. Symbol: Bh; atomic no: 107 hassiumHs108a synthetic element produced in small quantities by high-energy ion bombardment. Symbol: Hs; atomic no: 108 meitneriumMt109a synthetic element produced in small quantities by high-energy ion bombardment. Symbol: Mt; atomic no: 109 darmstadtiumDs110a synthetic radioactive element produced in small quantities by cold fusion in a linear accelerator. Symbol: Ds; atomic no: 110 roentgeniumRg111a synthetic radioactive element produced in small quantities by cold fusion in a linear accelerator. Symbol: Rg; atomic no: 111 coperniciumCn112a highly radioactive element that is produced synthetically. Symbol: Cn; atomic no: 112; atomic wt: 285 nihoniumNh113a highly radioactive element, of which only a few atoms have ever been produced. Symbol: Nh; atomic no: 113; atomic wt: 286 fleroviumFl114a transuranic element produced by bombarding plutonium with calcium-48 atoms. Symbol: Fl; atomic no: 114; atomic wt: 298 moscoviumMc115a highly radioactive element, of which only a few atoms have ever been produced. Symbol: Mc; atomic no: 115; atomic wt: 289 livermoriumLv116 a transuranic element produced by bombarding curium with calcium-20 ions. Symbol: Lv; atomic no: 116; atomic wt: 293 tennessineTs117a highly radioactive element, of which only a few atoms have ever been produced. Symbol: Ts; atomic no: 117; atomic wt: 294 oganessonOg118a highly radioactive element, of which only a few atoms have ever been produced. Symbol: Og; atomic no: 118; atomic wt: 294 ▷ See chemical
Copyright © 2016 by HarperCollins Publishers. All rights reserved.
Parola Elenco dei Chemical elements b> dal Elenchi di parole inglesi Collins