The Elements hydrogen Symbol: H Atomic number: 1 Atomic weight: 1.0079 Colourless, odourless gaseous checmical element. Lightest and most abundant element in the universe. Present in water and in all organic compounds. Chemically reacts with most elements. Discovered by Henry Cavendish in 1776. helium Symbol: He Atomic number: 2 Atomic weight: 4.0026 Colourless, odourless gaseous nonmetallic element. Belongs to group 18 of the periodic table. Lowest boiling point of all elements and can only be solidified under pressure. Chemically inert, no known compounds. Discovered in the solar spectrum in 1868 by Lockyer. lithium Symbol: Li Atomic number: 3 Atomic weight: 6.939 Socket silvery metal. First member of group 1 of the periodic table. Lithium salts are used in psychomedicine. beryllium Symbol: Be Atomic number: 4 Atomic weight: 9.0122 Grey metallic element of group 2 of the periodic table. Is toxic and can cause severe lung diseases and dermatitis. Shows high covalent character. It was isolated independently by F. Wohler and A.A. Bussy in 1828. boron Symbol: B Atomic number: 5 Atomic weight: 10.811 An element of group 13 of the periodic table. There are two allotropes, amorphous boron is a brown power, but metallic boron is black. The metallic form is hard (9.3 on Mohs' scale) and a bad conductor in room temperatures. It is never found free in nature. Boron-10 is used in nuclear reactor control rods and shields. It was discovered in 1808 by Sir Humphry Davy and by J.L. Gay-Lussac and L.J. Thenard. carbon Symbol: C Atomic number: 6 Atomic weight: 12.01115 Carbon is a member of group 14 of the periodic table. It has three allotropic forms of it, diamonds, graphite and fullerite. Carbon-14 is commonly used in radioactive dating. Carbon occurs in all organic life and is the basis of organic chemistry. Carbon has the interesting chemical property of being able to bond with itself, and a wide variety of other elements. nitrogen Symbol: N Atomic number: 7 Atomic weight: 14.0067 Colourless, gaseous element which belongs to group 15 of the periodic table. Constitutes ~78% of the atmosphere and is an essential part of the ecosystem. Nitrogen for industrial purposes is acquired by the fractional distallation of liquid air. Chemically inactive, reactive generally only at high temperatures or in electrical discharges. It was discovered in 1772 by D. Rutherford. oxygen Symbol: 15.9994 Atomic number: 8 Atomic weight: 15.9994 A colourless, odourless gaseous element belonging to group 16 of the periodic table. It is the most abundant element present in the earth's crust. It also makes up 28% of the Earth's atmosphere. For industrial purposes, it is seperated from liquid air by fractional distillation. It is used in high temperature welding, and in breathing. It commonly comes in the form of Oxygen, but is found as Ozone in the upper atmosphere. It was discovered by Priestley in 1774. fluorine Symbol: F Atomic number: 9 Atomic weight: 18.9984 A poisonous pale yellow gaseous element belonging to group 17 of the periodic table (The halogens). It is the most chemically reactive and electronegative element. It is highly dangerous, causing severe chemical burns on contact with flesh. Flourine was identified by Scheele in 1771 and first isolated by Moissan in 1886. neon Symbol: Ne Atomic number: 10 Atomic weight: 20.183 Colourless gaseous element of group 18 on the periodic table (noble gases). Neon occurs in the atmosphere, and comprises 0.0018% of the volume of the atmosphere. It has a distinct reddish glow when used in discharge tubes and neon based lamps. It forms almost no chemical compounds. Neon was discovered in 1898 by Sir William Ramsey and M.W. Travers. sodium Symbol: Na Atomic number: 11 Atomic weight: 22.9898 Soft silvery reactive element belonging to group 1 of the periodic table (alkali metals). It is highly reactive, oxidizing in air and reacting violenting with water, forcing it to be kept under oil. It was first isolated by Humphry Davy in 1807. magnesium Symbol: Mg Atomic number: 12 Atomic weight: 24.312 Silvery metallic element belonging to group 2 of the periodic table (alkaline-earth metals). It is essential for living organisms, and is used in a number og light alloys. Chemically very reactive, it forms a protective oxide coating when exposed to air and burns with an intense white flame. It also reacts with suphur, nitrogen and the halogens. First isolated by Bussy in 1828. aluminum Symbol: Al Atomic number: 13 Atomic weight: 26.9815 Silvery-white lustrous metallic element of group 3 of the periodic table. Highly reactive but protected by a thin transparent layer of the oxide which quickly forms in air. There are many alloys of aluminum, as well as a good number of industrial uses. Makes up 8.1% of the Earth's crust, by weight. Isolated in 1825 by H.C. Oersted. silicon Symbol: Si Atomic number: 14 Atomic weight: 28.086 Metalloid element belonging to group 14 of the periodic table. It is the second most abundant element in the Earth's crust, making up 25.7% of it by weight. Chemically less reactive than carbon. First identified by Lavoisier in 1787 and first isolated in 1823 by Berzelius. phosphorus Symbol: P Atomic number: 15 Atomic weight: 30.9738 Non-metallic element belonging to group 15 of the periodic table. Has a multiple allotropic forms. Essential element for living organisms. It was discovered by Brandt in 1669. sulphur Symbol: S Atomic number: 16 Atomic weight: 32.064 Yellow, nonmetallic element belonging to group 16 of the periodic table. It is an essential element in living organisms, needed in the amino acids cysteine and methionine, and hence in many proteins. Absorbed by plants from the soil as sulphate ion. chlorine Symbol: Cl Atomic number: 17 Atomic weight: 35.453 Halogen element. Poisonous greenish-yellow gas. Occurs widely in nature as sodium chloride in seawater. Reacts directly with many elements and compounds, strong oxidizing agent. Discovered by Karl Scheele in 1774. Humphry David confirmed it as an element in 1810. argon Symbol: Ar Atomic number: 18 Atomic weight: 39.948 Monatomic noble gas. Makes up 0.93% of the air. Colourless, odorless. Is inert and has no true compounds. Lord Rayleigh and Sir william Ramsey indentified argon in 1894. potassium Symbol: Na Atomic number: 19 Atomic weight: 22.9898 Soft silvery metallic element belonging to group 1 of the periodic table (alkali metals). Occurs naturally in sewater and a many minerals. Highly reactive, chemically, it resembles sodium in its behavior and compounds. Discovered by Sir Humphry Davy in 1807. calcium Symbol: Ca Atomic number: 20 Atomic weight: 40.08 Soft grey metallic element belonging to group 2 of the periodic table. Used a reducing agent in the extraction of thorium, zirconium and uranium. Essential element for living organisms. scandium Symbol: Sc Atomic number: 21 Atomic weight: 44.956 Rare soft silvery metallic element belonging to group 3 of the periodic table. There are ten isotopes, nine of which are radioactive and have short half-lives. Predicted in 1869 by Mendeleev, isolated by Nilson in 1879. titanium Symbol: Ti Atomic number: 22 Atomic weight: 47.90 White metallic transition element. Occurs in numerous minerals. Used in strong, light corroiion-resistant alloys. Forms a passive oxide coating when exposed to air. First discovered by Gregor in 1789. vanadium Symbol: V Atomic number: 23 Atomic weight: 50.942 Silvery-white metallic transition element. Occurs in a number of complex ores. Reacts chemically with nonmetals at high temperatures, and is not affected by hydrochloric acid or alkalis. Discovered in 1801 by del Rio who was persuaded that it was but impure chromium. It was rediscovered and named by Sefstrom in 1880. chromium Symbol: Cr Atomic number: 24 Atomic weight: 51.996 Hard silvery transition element. Used in decorative electroplating. Discovered in 1797 by Vauquelin. manganesse Symbol: Mn Atomic number: 25 Atomic weight: 54.938 Grey brittle metallic transition element. Rather electropositive, combines with some non-metals when heated. Discovered in 1774 by Scheele. iron Symbol: Fe Atomic number: 26 Atomic weight: 55.847 Silvery malleable and ductile metallic transition element. Has nine isotopes and is the fourth most abundant element in the earth's crust. Required by living organisms as a trace element (used in hemoglobin in humans.) Quite reactive, oxidizes in moist air, displaces hydrogen from dilute acids and combines with nonmetallic elements. cobalt Symbol: Co Atomic number: 27 Atomic weight: 58.993 Light grey transition element. Some metorites contain small amounts of metallic cobalt. Generally alloyed for use. Mammals require small amounts of cobalt salts. Cobalt-60, an artificially produced radioactive isotope of Cobalt is an important radioactive tracer and cancer-treatment agent. Discovered by G. Brandt in 1737. nickel Symbol: Ni Atomic number: 28 Atomic weight: 58.71 Malleable ductile silvery metallic transition element. Discovered by A.F. Cronstedt in 1751. copper Symbol: Cu Atomic number: 29 Atomic weight: 63.54 Red-brown transition element. Known by the Romans as 'cuprum.' Extracted and used for thousands of years. Malleable, ductile and an excellent conductor of heat and electriciy. When in moist conditions, a greenish layer forms on the outside. zinc Symbol: Zn Atomic number: 30 Atomic weight: 65.38 Blue-white metallic element. Occurs in multiple compounds naturally. Five stable isotopes are six radioactive isotopes have been found. Chemically a reactive metal, combines with oxygen and other nonmetals, reacts with dilute acids to release hydrogen. gallium Symbol: Ga Atomic number: 31 Atomic weight: 69.72 Soft silvery metallic element, belongs to group 13 of the periodic table. The two stable isotopes are Ga-69 and Ga-71. Eight radioactive isotopes are known, all having short half-lives. Gallium Arsenide is used as a semiconductor. Corrodes most other metals by diffusing into their lattice. First identified by Francois Lecoq de Boisbaudran in 1875. germanium Symbol: Ge Atomic number: 32 Atomic weight: 72.59 Lustrous hard metalloid element, belongs to group 14 of the periodic table. Forms a large number of organometallic compounds. Predicted by Mendeleev in 1871, it was actually founbd in 1886 by Winkler. arsenic Symbol: As Atomic number: 33 Atomic weight: 74.922 Metalloid element of group 15. There are three allotropes, yellow, black, and grey. Reacts with halogens, concentrated oxidizing acids and hot alkalis. Albertus Magnus is believed to have been the first to isolate the element in 1250. selenium Symbol: Se Atomic number: 34 Atomic weight: 78.96 Metalloid element, belongs to group 16 of the periodic table. Multiple allotropic forms exist. Chemically resembles sulphur. Discovered in 1817 by Jons J. Berzelius. bromine Symbol: Br Atomic number: 35 Atomic weight: 79.909 Halogen element. Red volitile liquid at room temperature. Its reactivity is somewhere between chlorine and iodine. Harmful to human tissue in a liquid state, the vapour irritates eyes and throat. Discovered in 1826 by Antoine Balard. krypton Symbol: Kr Atomic number: 36 Atomic weight: 83.80 Colorless gaseous element, belongs to the noble gases. Occurs in the air, 0.0001% by volume. It can be extracted from liquid air by fractional distallation. Generally not isolated, but used with other inert gases in flourescent lamps. Five natural isotopes, and five radioactive isotopes. Kr-85, the most stable radioactive isotope, has a half-life of 10.76 years and is produced in fission reactors. Practially inert, though known to form compounds with {flourine}. rubidium Symbol: Rb Atomic number: 37 Atomic weight: 85.47 Soft silvery metallic element, belongs to group 1 of the periodic table. Rb-97, the naturally occuring isotope, is radioactive. It is highly reactive, with properies similar to other elements in group 1, like igniting spontaneously in air. Discovered spectroscopically in 1861 by W. Bunsen and G.R. Kirchoff. strontium Symbol: Sr Atomic number: 38 Atomic weight: 87.62 Soft yellowish metallic element, belongs to group 2 of the periodic table. Highly reactive chemically. Sr-90 is present in radioactive fallout and has a half-life of 28 years. Discovered in 1798 by Klaproth and Hope, isolated in 1808 by Humphry Davy. yttrium Symbol: Y Atomic number: 39 Atomic weight: 88.905 Silvery-grey metallic element of group 3 on the periodic table. Found in uranium ores. The only natural isotope is Y-89, there are 14 other artificial isotopes. Chemically resembles the lanthanoids. Stable in the air below 400 degrees, celsius. Discovered in 1828 by Friedrich Wohler. zirconium Symbol: Zr Atomic number: 40 Atomic weight: 91.22 Grey-white metallic transition element. Five natural isotopes and six radioactive isotopes are known. Used in nuclear reactors for a {neutron} absorber. Discovered in 1789 by Martin Klaproth, isolated in 1824 by Berzelius. niobium Symbol: Nb Atomic number: 41 Atomic weight: 92.906 Soft, ductile grey-blue metallic transition element. Used in special steels and in welded joints to increase strength. Combines with halogens and oxidizes in air at 200 degrees celsius. Discovered by Charles Hatchett in 1801 and isolated by Blomstrand in 1864. Called {columbium} originally. molybdenum Symbol: Mo Atomic number: 42 Atomic weight: 95.94 Silvery, hard metallic transition element. Used in alloy steels. Chemically unreactive, not affected by most acids. Oxidizes at high temperatures. Discovered in 1778 by Scheele. technetium Symbol: Tc Atomic number: 43 Atomic weight: (98) Radioactive metallic transition element. Can be detected in some stars and the fission products of uranium. First made by Perrier and Segre by bombarding molybdenum with deutrons, giving them Tc-97. Tc-99 is the most stable isotope with a half-life of 2.6*10^6 years. Sixteen isotopes are known. Chemical properties are intermediate between rhenium and managanese. ruthenium Symbol: Ru Atomic number: 44 Atomic weight: 101.07 Hard white metallic transition element. Found with platinum, used as a catalyst in some platinum alloys. Dissolves in fused alkalis, and is not attacked by acids. Reacts with halogens and oxygen at high temperatures. Isolated in 1844 by K.K. Klaus. rhodium Symbol: Rh Atomic number: 45 Atomic weight: 102.905 Silvery white metallic transition element. Found with platinum and used in some platinum alloys. Not attacked by acids, dissolves only in aqua regia. Discovered in 1803 by W.H. Wollaston. palladium Symbol: Pd Atomic number: 46 Atomic weight: 106.4 Soft white ductile transition element. Found with some copper and nickel ores. Does not react with oxygen at normal temperatures. Dissolves slowly in hydrochloric acid. Discovered in 1803 by W.H. Wollaston. silver Symbol: Ag Atomic number: 47 Atomic weight: 107.870 White lustrous soft metallic transition element. Found in both its elemental form and in minerals. Used in jewellery, tableware and so on. Less reactive than silver, chemically. cadmium Symbol: Cd Atomic number: 48 Atomic weight: 112.40 Soft bluish metal belonging to group 12 of the periodic table. Extremely toxic even in low concentrations. Chemically similar to zinc, but lends itself to more complex compounds. Discovered in 1817 by F. Stromeyer. indium Symbol: In Atomic number: 49 Atomic weight: 114.82 Soft silvery element belonging to group 13 of the periodic table. The most common natural isotope is In-115, which has a half-life of 6*10^4 years. Five other radioisotopes exist. Discovered in 1863 by Reich and Richter. tin Symbol: Sn Atomic number: 50 Atomic weight: 118.69 Silvery malleable metallic element belonging to group 14 of the periodic table. Twenty-six isotopes are known, five of which are radioactive. Chemically reactive. Combines directly with chlorine and oxygen and displaces hydrogen from dilute acids. antimony Symbol: Sb Atomic number: 51 Atomic weight: 121.75 Element of group 15. Multiple allotropic forms. The stable form of antimony is a blue-white metal. Yellow and black antimony are unstable non-metals. Used in flame-proofing, paints, ceramics, enamels, and rubber. Attacked by oxidizing acids and halogens. First reported by Tholden in 1450. tellurium Symbol: Te Atomic number: 52 Atomic weight: 127.60 Silvery metalloid element of group 16. Eight natural isotopes, nine radioactive isotopes. Used in semiconductors and to a degree in some steels. Chemisty is similar to {sulphur}. Discovered in 1782 by Franz Miller. iodine Symbol: I Atomic number: 53 Atomic weight: 126.904 Drak violet nonmetallic element, belongs to group 17 of the periodic table. Insoluble in water. Required as a trace element for living organisms. One stable isotope, I-127 exists, in addition to fourteen radioactive isotopes. Chemically the least reactive of the halogens, and the most electropositive metallic halogen. Discovered in 1812 by Courtois. xenon Symbol: Xe Atomic number: 54 Atomic weight: 131.30 Colourless, odorless gas belonging to group 18 on the periodic table (the noble gases.) Nine natural isotopes and seven radioactive isotopes are known. Xenon was part of the first noble-gas compound synthesized. Serveral others involving Xenon have been found since then. Xenon was discovered by Ramsey and Travers in 1898. caesium Symbol: Cs Atomic number: 55 Atomic weight: 132.9054 Soft silvery-white metallic element belonging to group 1 of the periodic table. Cs-133 is the natural isotope. Fifteen other radioisotopes exist. Lowest ionization potential of all elements. barium Symbol: Ba Atomic number: 56 Atomic weight: 137.34 Silvery-white reactive element, belonging to group 2 of the periodic table. Soluble barium compounds are extremely poisonous. Identified in 1774 by Karl Scheele and extracted in 1808 by Humphry Davy. lanthanum Symbol: La Atomic number: 57 Atomic weight: 138.9055 (From the Greek word lanthanein, to line hidden) Silvery metallic element belonging to group 3 of the periodic table and oft considered to be one of the lanthanoids. Found in some rare-earth minerals. Twenty-five natural isotopes exist. La-139 which is stable, and La-138 which has a half-life of 10^10 to 10^15 years. The other twenty-three isotopes are radioactive. It resembles the lanthanoids chemically. Lanthanum has a low to moderate level of toxicity, and should be handled with care. Discovered in 1839 by C.G. Mosander. cerium Symbol: Ce Atomic number: 58 Atomic weight: 140.12 Silvery metallic element, belongs to the lanthanoids. Four natural isotopes exist, and fifteen radioactive isotopes have been identified. Used in some rare-earth alloys. The oxidized form is used in the glass industry. Discovered by Martin .H. Klaproth in 1803. praseodymium Symbol: Pr Atomic number: 59 Atomic weight: 140.907 Soft silvery metallic element, belongs to the lanthanoids. Only natural isotope is Pr-141 which is not radioactive. Fourteen radioactive isotopes have been artificially produced. Used in rare-earth alloys. Discovered in 1885 by C.A. von Welsbach. neodymium Symbol: Nd Atomic number: 60 Atomic weight: 144.24 Soft silvery metallic element, belongs to the lanthanoids. Seven natural isotopes, Nd-144 being the only radioactive one with a half-life of 10^10 to 10^15 years. Seven artificial radioisotopes have been produced. The metal is used in glassworks to color class a shade of violet-purple and make it dichroic. Used in some rare-earth alloys. Discovered by C.A. von Welsbach in 1885. promethium Symbol: Pm Atomic number: 61 Atomic weight: (147) Soft silvery metallic element, belongs to the lanthanoids. Pm-147, the only natural isotope, is radioactive and has a half-life of 252 years. Eighteen radioisotopes have been produced, but all have very short half-lives. Found only in nuclear decay waste. Pm-147 is of interest as a beta-decay source, however Pm-146 and Pm-148 have to be removed from it first, as they generate gamma radiation. Discovered by J.A. Marinsky, L.E. Glendenin and C.D. Coryell in 1947. samarium Symbol: Sm Atomic number: 62 Atomic weight: 150.35 Soft silvery metallic element, belongs to the lanthanoids. Seven natural isotopes, Sm-147 is the only radioisotope, and has a half-life of 2.5*10^11 years. Used for making special alloys needed in the production of nuclear reactors. Also used as a neutron absorber. Small quantities of samarium oxide is used in special optical glasses. The largest use of the element is its ferromagnetic alloy which produces permenant magnets that are five times stronger than magnets produced by any other material. Discovered by Francois Lecoq de Boisbaudran in 1879. europium Symbol: Eu Atomic number: 63 Atomic weight: 151.25 Soft silvery metallic element belonging to the lanthanoids. Eu-151 and Eu-153 are the only two stable isotopes, both of which are {neutron} absorbers. Discovered in 1889 by Sir William Crookes. gadolinium Symbol: Gd Atomic number: 64 Atomic weight: 157.25 Soft silvery metallic element belonging to the lanthanoids. Seven natural, stable isotopes are known in addition to eleven artificial isotopes. Gd-155 and Gd-157 and the best neutron absorbers of all elements. Gadolinium compounds are used in electronics. Discovered by J.C.G Marignac in 1880. terbium Symbol: Tb Atomic number: 65 Atomic weight: 158.924 Silvery metallic element belonging to the lanthanoids. Tb-159 is the only stable isotope, there are seventeen artificial isotopes. Discovered by G.G. Mosander in 1843. dysprosium Symbol: Dy Atomic number: 66 Atomic weight: 162.50 Soft silvery metallic element, belongs to the lanthanoids. Seven natural isotopes and twelve artificial isotopes. Limited use as a nuetron absorber in nuclear technology. Discovered by Francois Lecoq de Boisbaudran in 1886. holmium Symbol: Ho Atomic number: 67 Atomic weight: 167.26 Soft silvery metallic element, belongs to the lanthanoids. Occurs in some rare-earth minerals. One natural isotope, Ho-165 exists, eighteen artificial isotopes have been produced. No known uses for the element. Discovered by Per Theodor Cleve and J.L. Soret in 1879. erbium Symbol: Er Atomic number: 68 Atomic weight: 167.26 Soft silvery metallic element which belongs to the lanthanoids. Six natural isotopes that are stable. Twelve artificial isotopes are known. Used in nuclear technology as a neutron absorber. It is being investigated for other possible uses. Discovered by Carl G. Mosander in 1843. thulium Symbol: Tm Atomic number: 69 Atomic weight: 168.934 Soft grey metallic element that belongs to the lanthanoids. One natural isotope exists, Tm-169, and seventeen artificial isotopes have been produced. No known uses for the element. Discovered in 1879 by Per Theodor Cleve. ytterbium Symbol: Yb Atomic number: 70 Atomic weight: 173.04 Silvery metallic element of the lanthanoids. Seven natural isotopes and ten artificial isotopes are known. Used in certain steels. Discovered by J.D.G. Marignac in 1878. lutetium Symbol: Lu Atomic number: 71 Atomic weight: 194.97 Silvery metallic element, belongs to the lanthanoids. Least abundant of all the (natural) elements. Two natural isotopes exist, Lu-175, which is stable, and Lu-176 which has a half-life of 2.2*10^10 years. Used as a catalyst. Identified in 1907 by G. Urban. hafium Symbol: Hf Atomic number: 72 Atomic weight: 178.49 Silvery lustrous metallic transition element. Used in tungsten alloys in filaments and electrodes, also acts as a neutron absorber. First reported by Urbain in 1911, existance was finally established in 1923 by D. Coster, G.C. de Hevesy in 1923. tantalum Symbol: Ta Atomic number: 73 Atomic weight: 180.948 Heavy blue-grey metallic transition element. Ta-181 is a stable isotope, and Ta-180 is a radioactive isotope, with a half-life in excess of 10^7 years. Used in surgery as it is unreactive. Forms a passive oxide layer in air. Identified in 1802 by Ekeberg and isolated in 1820 by Jons J. Berzelius. tungsten Symbol: W Atomic number: 74 Atomic weight: 183.85 White or grey metallic transition element, formerly called {wolfram}. Forms a protective oxide in air and can be oxidized at high temperature. First isolated by Jose and Fausto de Elhuyer in 1783. rhenium Symbol: Re Atomic number: 75 Atomic weight: 186.2 Silvery-white metallic transition element. Obtained as a by-product of molybdenum refinement. Rhenium-molybdenum alloys are superconducting. osmium Symbol: Os Atomic number: 76 Atomic weight: 190.2 Hard blue-white metallic transition element. Found with platinum and used in some alloys with platinum and iridium. iridium Symbol: Ir Atomic number: 77 Atomic weight: 192.2 Silvery metallic transition element. Occurs with platinum. Discovered in 1804 by Tennant. platinum Symbol: Pt Atomic number: 78 Atomic weight: 195.09 Silvery white metallic transition element. Used in jewellery, laboratory apparatus, electrical contacts and in some alloys. Also a hydrogenation catalyst. Does not oxidize or dissolve in hydrochloric acid. gold Symbol: Au Atomic number: 79 Atomic weight: 196.967 Soft yellow malleable metallic transition element. Used in jewellery, dentistry, and electronics. Unreactive chemically. mercury Symbol: Hg Atomic number: 80 Atomic weight: 200.59 Heavy silvery liquid metallic element, belongs to the zind group. Used in thermometeres, barometeres and other scientific apparatus. Less reactive than zinc and cadmium, does not displace hydrogen from acids. Forms a number of complexes and organomercury compounds. thallium Symbol: Tl Atomic number: 81 Atomic weight: 204.37 Greyish metallic element, belongs to group 13. The naturally occuring isotopes are l-203 and Tl-205. Eleven radioactive isotopes have been identified. Used in some experiemtnal alloys and electronics. The sulphate form was used as a rodentcide at one time. Discovered by Sir William Crookes in 1861. lead Symbol: Pb Atomic number: 82 Atomic weight: 207.19 Heavy dull grey ductile metallic element, belongs to group 14. Used in building construction, lead-place accumulators, bullets and shot, and is part of solder, pewter, bearing metals, type metals and fusible alloys. bismuth Symbol: Bi Atomic number: 83 Atomic weight: 208.980 White crystalline metal with a pink tinge, belongs to group 15. Most diamagnetic of all metals and has the lowest thermal conductivity of all the elements except mercury. Lead-free bismuth compounds are used in cosmetics and medical procedures. Burns in the air and produces a blue flame. In 1753, C.G. Junine first demonstrated that it was different from lead. polonium Symbol: Po Atomic number: 84 Atomic weight: (210) Rare radioactive metallic element, belongs to group 16 of the periodic table. Over 30 known isotopes exist, the most of all elements. Po-209 has a half-life of 103 years. Possible uses in heating spacecraft. Discovered by Marie Curie in 1898 in a sample of pitchblende. astatine Symbol: At Atomic number: 85 Atomic weight: (210) Radioactive halogen element. Occurs naturally from uranium and thorium decay. At least 20 known isotopes. At-210, the most stable, has a half-life of 8.3 hours. Synthesized by nuclear bomardment in 1940 by D.R. Corson, K.R. MacKenzie and E. Segre at the University of California. radon Symbol: Rn Atomic number: 86 Atomic weight: (222) Colorless radioactive gaseous element, belongs to the noble gases. Twenty known isotopes, the most stable is Rn-222 with a half-life of 3.8 days. Forms by the decay of Radium-226. Used in radiotherapy. As a noble gas, it is effectivly inert, though radon flouride can be synthesized. First isolated in 1908 by Ramsey and Gray. francium Symbol: Fr Atomic number: 87 Atomic weight: (223) Radioactive element, belongs to group 1 of the periodic table. Found in uranium and thorium ores. The 22 known isotopes are all radioactive, with the most stable being Fr-223. Its existance was confirmed in 1939 by Marguerite Perey. radium Symbol: Ra Atomic number: 88 Atomic weight: (226) Radioactive metallic transuranic element, belongs to group 2 of the periodic table. Most stable isotope, Ra-226 has a half-life of 1602 years, which decays into radon. Isolated from pitchblende in 1898 Marie and Pierre Curie. actinium Symbol: Ac Atomic number: 89 Atomic weight: (227) Silvery radioactive metallic element, belongs to group 3 of the periodic table. The most stable isotope, Ac-227, has a half-life of 217 years. Ac-228 (half-life of 6.13 hours) also occurs in nature. There are 22 other artificial isotopes, all radioactive and having very short half-lives. Chemistry similer to lanthanum. Used as a source of alpha particles. Discovered by A. Debierne in 1899. thorium Symbol: Th Atomic number: 90 Atomic weight: 232.038 Grey radioactive metallic element. Belongs to actinoids. Found in monazite sand in Brazil, India and the US. Thorium-232 has a half-life of 1.39x10^10 years. Can be used as a nuclear fuel for breeder reactors. Thorium-232 captures slow {neutron}s and breeds uranium-233. Discovered by Jons J. Berzelius in 1829. protactinium Symbol: Pa Atomic number: 91 Atomic weight: (231) Radioactive metallic element, belongs to the actinoids. The most stable isotope, Pa-231 has a half-life of 2.43*10^4 years. At least 10 other radioactive isotopes are known. No practical applications are known. Discovered in 1917 by Lise Meitner and Otto Hahn. uranium Symbol: U Atomic number: 92 Atomic weight: (231) White radioactive metallic element belonging to the actinoids. Three natural isotopes, U-238, U-235 and U-234. Uranium-235 is used as the fuel for nuclear reactors and weapons. Discovered by Martin H. Klaproth in 1789. neptunium Symbol: Np Atomic number: 93 Atomic weight: (237) Radioactive metallic transuranic element, belongs to the actinoids. Np-237, the most stable isotope, has a half-life of 2.2*10^6 years and is a by product of nuclear reactors. The other known isotopes have mass numbers 229 through 236, and 238 through 241. Np-236 has a half-life of 5*10^3 years. First produced by Edwin M. McMillan and P.H. Abelson in 1940. plutonium Symbol: Pu Atomic number: 94 Atomic weight: (242) Dense silvery radioactive metallic transuranic element, belongs to the actinoids. Pu-244 is the most stable isotope with a half-life of 7.6*10^7 years. Thirteen isotopes are known. Pu-239 is the most important, it undergoes nuclear fission with slow neutrons and is hence important to nuclear weapons and reactors. Plutonium production is monitored down to the gram to prevent military misuse. First produced by Gleen T. Seaborg, Edwin M. McMillan, J.W. Kennedy and A.C. Wahl in 1940. americium Symbol: Am Atomic number: 95 Atomic weight: (243) Radioactive metallic transuranic element, belongs to the actinoids. Ten known isotopes. Am-243 is the most stable isotope, with a half-life of 7.95*10^3 years. Discovered by Glenn T. Seaborg and associates in 1945, it was obtained by bombarding {uranium}-238 with alpha particles. curium Symbol: Cm Atomic number: 96 Atomic weight: (247) Radioactive metallic transuranic element. Belongs to actinoid series. Nine known isotopes, Cm-247 has a half-life of 1.64*10^7 years. First identified by Glenn T. Seaborg and associates in 1944, first produced by L.B. Werner and I. Perlman in 1947 by bombarding americium-241 with {neutron}s. Named for Marie Curie. berkelium Symbol: Bk Atomic number: 97 Atomic weight: (247) Radioactive metallic transuranic element. Belongs to actinoid series. Eight known isotopes, the most common Bk-247, has a half-life of 1.4*10^3 years. First produced by Glenn T. Seaborg and associates in 1949 by bombarding americium-241 with alpha particles. californium Symbol: Cf Atomic number: 98 Atomic weight: (249) Radioactive metallic transuranic element. Belongs to actinoid series. Cf-251 has a half life of about 700 years. Nine isotopes are known. Cf-252 is an intense {neutron} source, which makes it an intense {neutron} source and gives it a use in {neutron} activation analysis and a possible use as a radiation source in medicine. First produced by Glenn T. Seaborg and associates in 1950. einsteinium Symbol: Es Atomic number: 99 Atomic weight: (254) Radioactive metallic transuranic element belonging to the actinoids. Es-254 has the longest half-life of the eleven known isotopes at 270 days. First identified by Albert Ghiorso and associates in the debris of the 1952 hydrogen bomb explosion. In 1961 the first microgram quantities were available. fermium Symbol: Fm Atomic number: 100 Atomic weight: (253) Radioactive metallic transuranic element, belongs to the actinoids. Ten known isotopes, most stable is Fm-257 with a half-life of 10 days. First identified by Albert Ghiorso and associates in the debris of the first hydrogen-bomb explosion in 1952. mendelevium Symbol: Md Atomic number: 101 Atomic weight: (256) Radioactive metallic transuranic element. Belongs to the actinoid series. Only known isotope, Md-256 has a half-life os 1.3 hours. First identified by Glenn T. Seaborg, Albert Ghiorso and associates in 1955. Alternative name {unnilunium} has been proposed. Named after the 'inventor' of the periodic table, Dmitri Mendeleev. nobelium Symbol: No Atomic number: 102 Atomic weight: (254) Radioactive metallic transuranic element, belongs to the actinoids. Seven known isotopes exist, the most stable being No-254 with a half-life of 255 seconds. First identified with certianty by Albert Ghiorso and Glenn T. Seaborg in 1966. {Unnilbium} has been proposed as an alternative name. lawrencium Symbol: Lr Atomic number: 103 Atomic weight: (262) Radioactive metallic transuranic element. Belongs to the actinoids series. Only one known isotope, Lr-257 has a half-life of 8 seconds. Identified in 1961 by Albert Ghiorso and associates. unnilquadium Symbol: Unq Atomic number: 104 Atomic weight: (261) Radioactive transactinide element. Expected to have similar chemical properties to those displayed by hafnium. Rf-260 was discovered by the Joint Nuclear Research Institute at Dubna (U.S.S.R.) in 1964. Researchers at Berkeley discovered Unq-257 and Unq-258 in 1964. unnilpentium Symbol: Unp Atomic number: 105 Atomic weight: (262) Radioactive transactinide element. Half-life of 1.6s. Discovered in 1970 by Berkeley researchers. So far, seven isotopes have been discovered. unnilhexium Symbol: Atomic number: 106 Atomic weight: (263) Half-life of 0.9 +/- 0.2 s. Discovered by the Joint Institute for Nuclear Research at Dubna (U.S.S.R.) in June of 1974. Its existance was confirmed by the Lawrence Berkeley Laboratory and Livermore National Labrotory in September of 1974. unnilseptium Symbol: Atomic number: 107 Atomic weight: (262) Radioactive transition metal. Half-life of approximately 1/500 s. Discovered by the Joint Institute for Nuclear Research at Dubna (U.S.S.R.) in 1976. Confirmed by West German physicists at the Heavy Ion Research Laboratory at Darmstadt. unniloctium Symbol: Uno Atomic number: 108 Atomic weight: (265) Radioactive transition metal. meitnerium Symbol: Mt Atomic number: 109 Atomic weight: (266) Half-life of approximatly 5ms. The creation of this element demonstrated that fusion techniques could indeed be used to make new, heavy nuclei. Made and identified by physicists of the Heavy Ion Research Laboratory, Darmstadt, West Germany in 1982. Named in honor of Lise Meitner the Austrian physicist. unnildecium Symbol: Unn Atomic number: 110 Atomic weight: (272)? Half-life of approximatly 10ms. Reported in 1994 by German researchers at Darmstadt, Germany. wolfram Original name for {tungsten}. cuprum Roman name for {copper}. columbium The original name for {niobium}. unnilunium Symbol: Unu Name proposed by the International Union of Pure and Applied Physics to settle the dispute over naming the 101st element {mendelvium}. unnilbium Symbol: Unb Name proposed by the International Union of Pure and Applied Physics to settle the dispute over naming the 102nd element {nobelium}. lawrencium Symbol: Lr Name proposed by the International Union of Pure and Applied Physics to settle the dispute over naming the 103rd element {lawrencium}. kurchatovium Symbol: Ku Competing name for {unnilquadium}, the 104th element, proposed by Russian scientists. dubnium Symbol: Db Competing name for {unnilquadium}, the 104th element, proposed by the IUPAC. rutherfordium Symbol: Rf Competing name for {unnilquadium}, the 104th element, proposed by the American Chemical Society. hahnium Symbol: Ha Competing name for {unnilpentium}, the 105th element, proposed by the American Chemical Society. Also a competing name for {unniloctium}, the 108th element, proposed by the IUPAC. Both were chosen in honor of German researcher, Otto Hahn. joliotium Symbol: Jl Competing name for {unnilpentium}, the 105th element, proposed by the IUPAC. seaborgium Name proposed for the 106th element ({unnilhexium}) by the American Chemical Society in honor of Gleen T. Seaborg, an American nuclear physicist and Nobel prize winner. nielsbohrium Competing name for {unnilseptium}, the 107th element, proposed by its West German discoverers and supported by the American Chemical Society. The name was chosen in honor of physicist, Niels Bohr. bohrium Competing name for {unnilseptium}, the 107th element, proposed by the IUPAC in response to the discoverers of the element wanting to name it {nielsbohrium}. hassium Competing name for {unniloctium}, the 108th element, proposed by its German discoverers and supported by the American Chemical Society. neutron Weight: 1.6749286*10^-27kg A neutral hadron that is stable in the atomic nucleus but decays into a protron, an electron and an antineutrino with a mean life of 12 minutes outside the nucleus. Neutronics exist in all atomic nuclei except normal hydrogen. Reported in 1932 by James Chadwick. deuterium Symbol: D Atomic Weight: 2 A {hydrogen} atom which has but one proton and {neutron}. Deuterium makes up about 0.015% of all natural hydrogen. Chemical properties are like that of normal {hydrogen}, though somewhat slower.