actiniumAca 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 aluminiumAla light malleable ductile silvery-white metallic element that resists corrosion; the third most abundant element in the earth's crust (8.1 per cent), occurring only as a compound, principally in bauxite. It is used, esp in the form of its alloys, in aircraft parts, kitchen utensils, etc. Symbol: Al; atomic no: 13; atomic wt: 26.9815; valency: 3; relative density: 2.699; melting pt: 660.45°C; boiling pt: 2520°CamericiumAma 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) bariumBaa soft silvery-white metallic element of the alkaline earth group. It is used in bearing alloys and compounds used as pigments. Symbol: Ba; atomic no: 56; atomic wt: 137.327; valency: 2; relative density: 3.5; melting pt: 729°C; boiling pt: 1805°CberkeliumBka 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) berylliumBea corrosion-resistant toxic silvery-white metallic element that occurs chiefly in beryl and is used mainly in X-ray windows and in the manufacture of alloys. Symbol: Be; atomic no: 4; atomic wt: 9.012; valency: 2; relative density: 1.848; melting pt: 1289°C; boiling pt: 2472°CbismuthBia brittle pinkish-white crystalline metallic element having low thermal and electrical conductivity, which expands on cooling. It is widely used in alloys, esp low-melting alloys in fire safety devices; its compounds are used in medicines. Symbol: Bi; atomic no: 83; atomic wt: 208.98037; valency: 3 or 5; relative density: 9.747; melting pt: 271.4°C; boiling pt: 1564±5°CbohriumBha transuranic element artificially produced in minute quantities by bombarding 204Bi atoms with 54Cr nuclei. Symbol: Bh; atomic no: 107cadmiumCda 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 caesium or (U.S.) cesiumCsa ductile silvery-white element of the alkali metal group that is the most electropositive metal. It occurs in pollucite and lepidolite and is used in photocells. The radioisotope caesium-137, with a half-life of 30.2 years, is used in radiotherapy. Symbol: Cs; atomic no: 55; atomic wt: 132.90543; valency: 1; relative density: 1.873; melting pt: 28.39±0.01°C; boiling pt: 671°C calciumCaa malleable silvery-white metallic element of the alkaline earth group; the fifth most abundant element in the earth's crust (3.6 per cent), occurring esp as forms of calcium carbonate. It is an essential constituent of bones and teeth and is used as a deoxidizer in steel. Symbol: Ca; atomic no: 20; atomic wt: 40.078; valency: 2; relative density: 1.55; melting pt: 842±2°C; boiling pt: 1494°CcaliforniumCfa metallic transuranic element artificially produced from curium. Symbol: Cf; atomic no: 98; half-life of most stable isotope, 251Cf: 800 years (approx.) ceriumCea malleable ductile steel-grey element of the lanthanide series of metals, used in lighter flints and as a reducing agent in metallurgy. Symbol: Ce; atomic no: 58; atomic wt: 140.115; valency: 3 or 4; relative density: 6.770; melting pt: 798°C; boiling pt: 3443°C chromiumCra hard grey metallic element that takes a high polish, occurring principally in chromite: used in steel alloys and electroplating to increase hardness and corrosion-resistance. Symbol: Cr; atomic no: 24; atomic wt: 51.9961; valency: 2, 3, or 6; relative density: 7.18–7.20; melting pt: 1863±20°C; boiling pt: 2672°CcobaltCoa brittle hard silvery-white element that is a ferromagnetic metal: occurs principally in cobaltite and smaltite and is widely used in alloys. The radioisotope cobalt-60, with a half-life of 5.3 years, is used in radiotherapy and as a tracer. Symbol: Co; atomic no: 27; atomic wt: 58.93320; valency: 2 or 3; relative density: 8.9; melting pt: 1495°C; boiling pt: 2928°C coperniciumCnhighly radioactive element that is produced synthetically. Symbol: Cn; atomic no: 112; atomic wt: 285 copperCua malleable ductile reddish metallic element occurring as the free metal, copper glance, and copper pyrites: used as an electrical and thermal conductor and in such alloys as brass and bronze. Symbol: Cu; atomic no: 29; atomic wt: 63.546; valency: 1 or 2; relative density: 8.96; melting pt: 1084.87±+0.2°C; boiling pt: 2563°C curiumCma 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 dubniumDua synthetic transactinide element produced in minute quantities by bombarding plutonium with high-energy neon ions. Symbol: Du; atomic no 105.dysprosiumDya soft silvery-white metallic element of the lanthanide series: used in laser materials and as a neutron absorber in nuclear control rods. Symbol: Dy; atomic no: 66; atomic wt: 162.50; valency: 3; relative density: 8.551; melting pt: 1412°C; boiling pt: 2567°CeinsteiniumEsa metallic transuranic element artificially produced from plutonium. Symbol: Es; atomic no: 99; half-life of most stable isotope, 252Es: 276 days erbiumEra soft malleable silvery-white element of the lanthanide series of metals: used in special alloys, room-temperature lasers, and as a pigment. Symbol: Er; atomic no: 68; atomic wt: 167.26; valency: 3; relative density: 9.006; melting pt: 1529°C; boiling pt: 2868°C europiumEua soft ductile reactive silvery-white element of the lanthanide series of metals: used as the red phosphor in colour television and in lasers. Symbol: Eu; atomic no: 63; atomic wt: 151.965; valency: 2 or 3; relative density: 5.244; melting pt: 822°C; boiling pt: 1527°C fermiumFma transuranic element artificially produced by neutron bombardment of plutonium. Symbol: Fm; atomic no: 100; half-life of most stable isotope, 257Fm: 80 days (approx.) franciumFran 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 gadoliniumGda ductile malleable silvery-white ferromagnetic element of the lanthanide series of metals: occurs principally in monazite and bastnaesite. Symbol: Gd; atomic no: 64; atomic wt: 157.25; valency: 3; relative density: 7.901; melting pt: 1313±°C; boiling pt: 3273°C (approx.) galliumGaa silvery metallic element that is liquid for a wide temperature range. It occurs in trace amounts in some ores and is used in high-temperature thermometers and low-melting alloys. Gallium arsenide is a semiconductor. Symbol: Ga; atomic no: 31; atomic wt: 69.723; valency: 2 or 3; relative density: 5.904; melting pt: 29.77°C; boiling pt: 2205°CgoldAua dense inert bright yellow element that is the most malleable and ductile metal, occurring in rocks and alluvial deposits: used as a monetary standard and in jewellery, dentistry, and plating. The radioisotope gold-198 (radiogold), with a half-life of 2.69 days, is used in radiotherapy. Symbol: Au; atomic no: 79; atomic wt: 196.96654; valency: 1 or 3; relative density: 19.3; melting pt: 1064.43°C; boiling pt: 2857°C hafniumHfa 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 hassiumHsa synthetic element produced in small quantities by high-energy ion bombardment. Symbol: Hs; atomic no: 108 holmiumHoa 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 indiumIna 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 iridiumIra 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 ironFea malleable ductile silvery-white ferromagnetic metallic element occurring principally in haematite and magnetite. It is widely used for structural and engineering purposes. Symbol: Fe; atomic no: 26; atomic wt: 55.847; valency: 2,3,4, or 6; relative density: 7.874; melting pt: 1538°C; boiling pt: 2862°C lanthanumLaa silvery-white ductile metallic element of the lanthanide series, occurring principally in bastnaesite and monazite: used in pyrophoric alloys, electronic devices, and in glass manufacture. Symbol: La; atomic no: 57; atomic wt: 138.9055; valency: 3; relative density: 6.145; melting pt: 918°C; boiling pt: 3464°ClawrenciumLra transuranic element artificially produced from californium. Symbol: Lr; atomic no: 103; half-life of most stable isotope, 256Lr: 35 seconds; valency: 3 leadPba heavy toxic bluish-white metallic element that is highly malleable: occurs principally as galena and used in alloys, accumulators, cable sheaths, paints, and as a radiation shield. Symbol: Pb; atomic no: 82; atomic wt: 207.2; valency: 2 or 4; relative density: 11.35; melting pt: 327.502°C; boiling pt: 1750°C lithiumLia soft silvery element of the alkali metal series: the lightest known metal, used as an alloy hardener, as a reducing agent, and in batteries. Symbol: Li; atomic no: 3; atomic wt: 6.941; valency: 1; relative density: 0.534; melting pt: 180.6°C; boiling pt: 1342°C lutetiumLua silvery-white metallic element of the lanthanide series, occurring in monazite and used as a catalyst in cracking, alkylation, and polymerization. Symbol: Lu; atomic no: 71; atomic wt: 174.967; valency: 3; relative density: 9.841; melting pt: 1663°C; boiling pt: 3402°CmagnesiumMga light silvery-white metallic element of the alkaline earth series that burns with an intense white flame, occurring principally in magnesite, dolomite, and carnallite: used in light structural alloys, flashbulbs, flares, and fireworks. Symbol: Mg; atomic no: 12; atomic wt: 24.3050; valency: 2; relative density: 1.738; melting pt: 650°C; boiling pt: 1090°CmanganeseMna brittle greyish-white metallic element that exists in four allotropic forms, occurring principally in pyrolusite and rhodonite: used in making steel and ferromagnetic alloys. Symbol: Mn; atomic no: 25; atomic wt: 54.93805; valency: 1, 2, 3, 4, 6, or 7; relative density: 7.21–7.44; melting pt: 1246±3°C; boiling pt: 2062°CmendeleviumMda 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 mercuryHga heavy silvery-white toxic liquid metallic element occurring principally in cinnabar: used in thermometers, barometers, mercury-vapour lamps, and dental amalgams. Symbol: Hg; atomic no: 80; atomic wt: 200.59; valency: 1 or 2; relative density: 13.546; melting pt: –38.842°C; boiling pt: 357°CmolybdenumMoa very hard ductile silvery-white metallic element occurring principally in molybdenite: used mainly in alloys, esp to harden and strengthen steels. Symbol: Mo; atomic no: 42; atomic wt: 95.94; valency: 2–6; relative density: 10.22; melting pt: 2623°C; boiling pt: 4639°CneodymiumNda toxic silvery-white metallic element of the lanthanide series, occurring principally in monazite: used in colouring glass. Symbol: Nd; atomic no: 60; atomic wt: 144.24; valency: 3; relative density: 6.80 and 7.00 (depending on allotrope); melting pt: 1024°C; boiling pt: 3127°CneptuniumNpa 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) nickelNi a malleable ductile silvery-white metallic element that is strong and corrosion-resistant, occurring principally in pentlandite and niccolite: used in alloys, esp in toughening steel, in electroplating, and as a catalyst in organic synthesis. Symbol: Ni; atomic no: 28; atomic wt: 58.6934; valency: 0, 1, 2, or 3; relative density: 8.902; melting pt: 1455°C; boiling pt: 2914°CniobiumNba ductile white superconductive metallic element that occurs principally in columbite and tantalite: used in steel alloys. Symbol: Nb; atomic no: 41; atomic wt: 92.90638; valency: 2, 3, or 5; relative density: 8.57; melting pt: 2469±10°C; boiling pt: 4744°CnobeliumNoa 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 osmiumOsa 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 palladiumPda 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 platinumPta 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 plutoniumPua 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 poloniumPoa 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 potassiumKa 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 praseodymiumPra 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 promethiumPma 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.) protactiniumPaa 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 radiumRaa 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 rheniumRea 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) rhodiumRha 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 rubidiumRba soft highly reactive radioactive element of the alkali metal group; the 16th most abundant element in the earth's crust (310 parts per million), occurring principally in pollucite, carnallite, and lepidolite. It is used in electronic valves, photocells, and special glass. Symbol: Rb; atomic no: 37; atomic wt: 85.4678; half-life of 87Rb: 5 × 1011 years; valency: 1, 2, 3, or 4; relative density: 1.532 (solid), 1.475 (liquid); melting pt: 39.48°C; boiling pt: 688°C rutheniumRua 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 samariumSma 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°CscandiumSca rare light silvery-white metallic element occurring in minute quantities in numerous minerals. Symbol: Sc; atomic no: 21; atomic wt: 44.955910; valency: 3; relative density: 2.989; melting pt: 1541°C; boiling pt: 2836°CseaborgiumSga synthetic transuranic element, synthesized and identified in 1974. Symbol: Sg; atomic no: 106silverAga 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 sodiumNaa 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 strontiumSra soft silvery-white element of the alkaline earth group of metals, occurring chiefly in celestite and strontianite. Its compounds burn with a crimson flame and are used in fireworks. The radioisotope strontium-90, with a half-life of 28.1 years, is used in nuclear power sources and is a hazardous nuclear fall-out product. Symbol: Sr; atomic no: 38; atomic wt: 87.62; valency: 2; relative density: 2.54; melting pt: 769°C; boiling pt: 1384°C tantalumTaa 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 technetiumTca 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 terbiumTba soft malleable silvery-grey element of the lanthanide series of metals, occurring in gadolinite and monazite and used in lasers and for doping solid-state devices. Symbol: Tb; atomic no: 65; atomic wt: 158.92534; valency: 3 or 4; relative density: 8.230; melting pt: 1356°C; boiling pt: 3230°C thalliumTla soft malleable highly toxic white metallic element used as a rodent and insect poison and in low-melting glass. Its compounds are used as infrared detectors and in photoelectric cells. Symbol: Tl; atomic no: 81; atomic wt: 204.3833; valency: 1 or 3; relative density: 11.85; melting pt: 304°C; boiling pt: 1473±10°CthoriumTha 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 thuliumTma malleable ductile silvery-grey element occurring principally in monazite. The radioisotope thulium-170 is used as an electron source in portable X-ray units. Symbol: Tm; atomic no: 69; atomic wt: 168.93421; valency: 3; relative density: 9.321; melting pt: 1545°C; boiling pt: 1950°CtinSna 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 titaniumTia strong malleable white metallic element, which is very corrosion-resistant and occurs in rutile and ilmenite. It is used in the manufacture of strong lightweight alloys, esp aircraft parts. Symbol: Ti; atomic no: 22; atomic wt: 47.88; valency: 2, 3, or 4; relative density: 4.54; melting pt: 1670±10°C; boiling pt: 3289°Ctungsten or wolframWa hard malleable ductile greyish-white element. It occurs principally in wolframite and scheelite and is used in lamp filaments, electrical contact points, X-ray targets, and, alloyed with steel, in high-speed cutting tools. Symbol: W; atomic no: 74; atomic wt: 183.85; valency: 2–6; relative density: 19.3; melting pt: 3422±20°C; boiling pt: 5555°CuraniumUa radioactive silvery-white metallic element of the actinide series. It occurs in several minerals including pitchblende, carnotite, and autunite and is used chiefly as a source of nuclear energy by fission of the radioisotope uranium-235. Symbol: U; atomic no: 92; atomic wt: 238.0289; half-life of most stable isotope, 238U: 451 × 109 years; valency: 2-6; relative density: 18.95 (approx.); melting pt: 1135°C; boiling pt: 4134°CvanadiumVa toxic silvery-white metallic element occurring chiefly in carnotite and vanadinite and used in steel alloys, high-speed tools, and as a catalyst. Symbol: V; atomic no: 23; atomic wt: 50.9415; valency: 2–5; relative density: 6.11; melting pt: 1910±10°C; boiling pt: 3409°CytterbiumYba soft malleable silvery element of the lanthanide series of metals that occurs in monazite and is used to improve the mechanical properties of steel. Symbol: Yb; atomic no: 70; atomic wt: 173.04; valency: 2 or 3; relative density: 6.903 (alpha), 6.966 (beta); melting pt: 819°C; boiling pt: 1196°C yttriumYa silvery metallic element occurring in monazite and gadolinite and used in various alloys, in lasers, and as a catalyst. Symbol: Y; atomic no: 39; atomic wt: 88.90585; valency: 3; relative density: 4.469; melting pt: 1522°C; boiling pt: 3338°CzincZna 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 zirconiumZra 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 ▷ See metal
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Word List of metal: elements from the Collins English Word Lists