Periodic Elements

(Mt) Meitnerium Element 109, meitnerium, is a synthetic element that is not present in the environment at all. There is no dispute concerning the name meitnerium for element 109. The interested reader should consult the on-line version of The Wonderful World of Atoms and Nuclei for a fascinating insight into research on "super-heavy" atoms.

Name: meitnerium Symbol: Mt Atomic number: 109 Relative atomic mass (Ar): [ 276 ] Standard state: presumably a solid at 298 K Color: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic Group in periodic table: 9 Group name: (none) Period in periodic table: 7 Block in periodic table: d-block Electron shell structure: 2.8.18.32.32.15.2 CAS Registry ID: 54038-01-6

(Cs) Caesium Caesium is known as cesium in the USA. The metal is characterized by a spectrum containing two bright lines in the blue (accounting for its name). It is silvery gold, soft, and ductile. It is the most electropositive and most alkaline element. Caesium, gallium, and mercury are the only three metals that are liquid at or around room temperature. Caesium reacts explosively with cold water, and reacts with ice at temperatures above -116°C. Caesium hydroxide is a strong base and attacks glass.

Name: caesium Symbol: Cs Atomic number: 55 Relative atomic mass (Ar): 132.9054519 (2) Standard state: solid at 298 K (but melts only slightly above this temperature) Color: silvery gold Classification: Metallic Group in periodic table: 1 Group name: Alkali metal Period in periodic table: 6 Block in periodic table: s-block Electron shell structure: 2.8.18.18.8.1 CAS Registry ID: 7440-46-2

(Cl) Chlorine Chlorine is a greenish yellow gas which combines directly with nearly all elements. Chlorine is a respiratory irritant. The gas irritates the mucous membranes and the liquid burns the skin. As little as 3.5 ppm can be detected as an odor, and 1000 ppm is likely to be fatal after a few deep breaths. It was used as a war gas in 1915. It is not found in a free state in nature, but is found commonly as NaCl (solid or seawater).

Name: chlorine Symbol: Cl Atomic number: 17 Relative atomic mass (Ar): 35.453 (2) [see notes g m] Standard state: gas at 298 K Color: yellowish green Classification: Non-metallic Group in periodic table: 17 Group name: Halogen Period in periodic table: 3 Block in periodic table: p-block Electron shell structure: 2.8.7 CAS Registry ID: 7782-50-5

(Db) Dubnium Dubnium is a synthetic element that is not present in the environment at all. It has no uses.

Name: dubnium Symbol: Db Atomic number: 105 Relative atomic mass (Ar): [ 268 ] Standard state: presumably a solid at 298 K Color: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic Group in periodic table: 5 Group name: (none) Period in periodic table: 7 Block in periodic table: d-block Electron shell structure: 2.8.18.32.32.11.2 CAS Registry ID: 53850-35-4

(Sn) Tin Ordinary tin is a silvery-white metal, is malleable, somewhat ductile, and has a highly crystalline structure. Due to the breaking of these crystals, a "tin cry" is heard when a bar is bent. The element has two allotropic forms. On warming, grey, or α-tin, with a cubic structure, changes at 13.2°C into white, or β-tin, the ordinary form of the metal. White tin has a tetragonal structure. When tin is cooled below 13.2°C, it changes slowly from white to grey. This change is affected by impurities such as aluminum and zinc, and can be prevented by small additions of antimony or bismuth. The conversion was first noted as growths on organ pipes in European cathedrals, where it was thought to be the devils work. This conversion was also speculated to be caused microorganisms and was called "tin plague" or "tin disease". Tin resists distilled, sea, and soft tap water, but is attacked by strong acids, alkalis, and acid salts. Oxygen in solution accelerates the attack. When heated in air, tin forms SnO2. It is, or was, used to plate steel, making "tin cans". Tin is used as one component in bell metals.

Name: tin Symbol: Sn Atomic number: 50 Relative atomic mass (Ar): 118.710 (7) [see note g] Standard state: solid at 298 K Color: silvery lustrous grey Classification: Metallic Group in periodic table: 14 Group name: (none) Period in periodic table: 5 Block in periodic table: p-block Electron shell structure: 2.8.18.18.4 CAS Registry ID: 7440-31-5

(W) Tungsten Pure tungsten is a steel-gray to tin-white metal. Tungsten has the highest melting point and lowest vapor pressure of all metals, and at temperatures over 1650°C has the highest tensile strength. The metal oxidizes in air and must be protected at elevated temperatures. It has excellent corrosion resistance and is attacked only slightly by most mineral acids.

Name: tungsten Symbol: W Atomic number: 74 Relative atomic mass (Ar): 183.84 (1) Standard state: solid at 298 K Color: grayish white, lustrous Classification: Metallic Group in periodic table: 6 Group name: (none) Period in periodic table: 6 Block in periodic table: d-block Electron shell structure: 2.8.18.32.12.2 CAS Registry ID: 7440-33-7

(Uuo) Experiments conducted at Dubna in Russia at the Flerov Laboratory of Nuclear Reactions (by workers from the Joint Institute for Nuclear Research in Russia and the Lawrence Livermore National Laboratory in the USA) indicate that element 118 (ununoctium, Uuo) was produced. Not too much though, one atom in the spring of 2002 and two more in 2005.

Name: ununoctium Symbol: Uuo Atomic number: 118 Relative atomic mass (Ar): [ 294 ] Standard state: presumably a gas at 298 K Color: unknown, but probably a colorless gas Classification: Non-metallic Group in periodic table: 18 Group name: Noble gas Period in periodic table: 7 Block in periodic table: p-block Electron shell structure: 2.8.18.32.32.18.8 CAS Registry ID: 54144-19-3

(Al) Aluminum Pure aluminum is a silvery-white metal with many desirable characteristics. It is light, nontoxic (as the metal), nonmagnetic and non-sparking. It is somewhat decorative. It is easily formed, machined, and cast. Pure aluminum is soft and lacks strength, but alloys with small amounts of copper, magnesium, silicon, manganese, and other elements have very useful properties. Aluminum is an abundant element in the earth's crust, but it is not found free in nature. The Bayer process is used to refine aluminum from bauxite, an aluminum ore.

Name: aluminium Symbol: Al Atomic number: 13 Relative atomic mass (Ar): 26.9815386 (8) Standard state: solid at 298 K Color: silvery Classification: Metallic Group in periodic table: 13 Group name: (none) Period in periodic table: 3 Block in periodic table: p-block Electron shell structure: 2.8.3 CAS Registry ID: 7429-90-5

(Lv) Livermorium An isotope of livermorium, 292Lv, was identified in the reaction of 248Cm with 48Ca. It is very short lived and decomposes to a known isotope of element 114, 288114Fl.

Name: livermorium Symbol: Lv Atomic number: 116 Relative atomic mass (Ar): [ 293 ] Standard state: presumably a solid at 298 K Color: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic Group in periodic table: 16 Group name: Chalcogen Period in periodic table: 7 Block in periodic table: p-block Electron shell structure: 2.8.18.32.32.18.6 CAS Registry ID: 54100-71-9

(Zr) Zirconium Zirconium is a grayish-white lustrous metal. The finely divided metal can ignite spontaneously in air, especially at elevated temperatures. The solid metal is much more difficult to ignite. The inherent toxicity of zirconium compounds is low. Hafnium is invariably found in zirconium ores, and the separation is difficult. Commercial grade zirconium contains from 1 to 3% hafnium. The hafnium is removed from the zirconium used in the nuclear power industry. Zirconium is found in S-type stars, and has been identified in the sun and meteorites. Analyses of lunar rock samples show a surprisingly high zirconium oxide content as compared with terrestrial rocks. Some forms of zircon (ZrSiO4) have excellent gemstone qualities.

Name: zirconium Symbol: Zr Atomic number: 40 Relative atomic mass (Ar): 91.224 (2) Standard state: solid at 298 K Color: silvery white Classification: Metallic Group in periodic table: 4 Group name: (none) Period in periodic table: 5 Block in periodic table: d-block Electron shell structure: 2.8.18.10.2 CAS Registry ID: 7440-67-7

(Sb) Antimony Metallic antimony is an extremely brittle metal of a flaky, crystalline texture. It is bluish white and has a metallic luster. It is not acted on by air at room temperature, but burns brilliantly when heated with the formation of white fumes. It is a poor conductor of heat and electricity. Antimony and its compounds are toxic. It is found mostly with other minerals and in stibnite.

Name: antimony Symbol: Sb Atomic number: 51 Relative atomic mass (Ar): 121.760 (1) [see note g] Standard state: solid at 298 K Color: silvery lustrous grey Classification: Semi-metallic Group in periodic table: 15 Group name: Pnictogen Period in periodic table: 5 Block in periodic table: p-block Electron shell structure: 2.8.18.18.5 CAS Registry ID: 7440-36-0

(Ar) Argon Argon is a colorless and odorless gas present to a very small extent in the atmosphere. Argon is very inert (indeed it is referred to as one of the noble gases) and is not known to form true chemical compounds. It makes a good atmosphere for working with air-sensitive materials since it is heavier than air and less reactive than N2. Today, the chemical symbol for argon is Ar but until 1957 its symbol was simply A.

Name: argon Symbol: Ar Atomic number: 18 Relative atomic mass (Ar): 39.948 (1) [see notes g r] Standard state: gas at 298 K Color: colorless Classification: Non-metallic Group in periodic table: 18 Group name: Noble gas Period in periodic table: 3 Block in periodic table: p-block Electron shell structure: 2.8.8 CAS Registry ID: 7440-37-1

(As) Arsenic Elemental arsenic occurs in two solid modifications: yellow, and grey or metallic, with specific gravities of 1.97, and 5.73, respectively. The element is a steel grey, very brittle, crystalline, semi metallic (metalloid) solid. It tarnishes in air, and when heated rapidly oxidizes to arsenous oxide which has a garlic odor. Arsenic and its compounds are poisonous as any reader of "who-done-it" books knows. Upon heating arsenic and some minerals containing arsenic, it sublimes (transfers from the solid to the gaseous state, without passing through the liquid state).

Name: arsenic Symbol: As Atomic number: 33 Relative atomic mass (Ar): 74.92160 (2) Standard state: solid at 298 K Color: metallic grey Classification: Semi-metallic Group in periodic table: 15 Group name: Pnictogen Period in periodic table: 4 Block in periodic table: p-block Electron shell structure: 2.8.18.5 CAS Registry ID: 7440-38-2

(At) Astatine The longest-lived isotope, 210At, has a half-life of only 8.3 hours. There are about 20 isotopes known, all of which are radioactive. Astatine is a halogen and possibly accumulates in the thyroid like iodine.

Name: astatine Symbol: At Atomic number: 85 Relative atomic mass (Ar): [ 210 ] Standard state: solid at 298 K Color: metallic Classification: Semi-metallic Group in periodic table: 17 Group name: Halogen Period in periodic table: 6 Block in periodic table: p-block Electron shell structure: 2.8.18.32.18.7 CAS Registry ID: 7440-68-8

(Ba) Barium Barium is a metallic element, soft, and when pure is silvery white like lead. The metal oxidizes very easily and it reacts with water or alcohol. Barium is one of the alkaline-earth metals. Small amounts of barium compounds are used in paints and glasses. Barium salts impart green colors to flames. The picture above shows the color arising from adding barium chlorate (BaClO3) to a burning mixture (only to be carried out by a professionally qualified chemist).

Name: barium Symbol: Ba Atomic number: 56 Relative atomic mass (Ar): 137.327 (7) Standard state: solid at 298 K Color: silvery white Classification: Metallic Group in periodic table: 2 Group name: Alkaline earth metal Period in periodic table: 6 Block in periodic table: s-block Electron shell structure: 2.8.18.18.8.2 CAS Registry ID: 7440-39-3

(Be) Beryllium Beryllium is a Group 2 (IIA) element. It is a metal and has a high melting point. At ordinary temperatures, beryllium resists oxidation in air. Beryllium compounds are very toxic. Its ability to scratch glass is probably due to the formation of a thin layer of the oxide. Aquamarine and emerald are precious forms of the mineral beryl, [Be3Al2(SiO3)6]. Its chemistry is dominated by its tendency to lose an electron to form Be2+. As this ion is so small it is highly polarizing, to the extent that its compounds are rather covalent. Its small size means that its complexes tend to be tetrahedral rather than octahedral.

Name: beryllium Symbol: Be Atomic number: 4 Relative atomic mass (Ar): 9.012182 (3) Standard state: solid at 298 K Color: lead grey Classification: Metallic Group in periodic table: 2 Group name: Alkaline earth metal Period in periodic table: 2 Block in periodic table: s-block Electron shell structure: 2.2 CAS Registry ID: 7440-41-7

(Bi) Bismuth Bismuth is a white, crystalline, brittle metal with a pinkish tinge. Bismuth is the most diamagnetic of all metals, and the thermal conductivity is lower than any metal, except mercury. It has a high electrical resistance, and has the highest Hall effect of any metal (that is, the greatest increase in electrical resistance when placed in a magnetic field).

Name: bismuth Symbol: Bi Atomic number: 83 Relative atomic mass (Ar): 208.98040 (1) Standard state: solid at 298 K Color: lustrous reddish white Classification: Metallic Group in periodic table: 15 Group name: Pnictogen Period in periodic table: 6 Block in periodic table: p-block Electron shell structure: 2.8.18.32.18.5 CAS Registry ID: 7440-69-9

(Bh) Bohrium Bohrium is a synthetic element that is not present in the environment at all. The German discoverers at GSI proposed the name Nielsbohrium (symbol Ns) after Niels Bohr. IUPAC are happy to name an element after Bohr but suggest bohrium (Bh) on the grounds that the first name of a person does not appear in the names of any other element named after a person. This seems to have been accepted by all concerned. The interested reader should consult the on-line version of The Wonderful World of Atoms and Nuclei for a fascinating insight into research on "super-heavy" atoms.

Name: bohrium Symbol: Bh Atomic number: 107 Relative atomic mass (Ar): [ 272 ] Standard state: presumably a solid at 298 K Color: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic Group in periodic table: 7 Group name: (none) Period in periodic table: 7 Block in periodic table: d-block Electron shell structure: 2.8.18.32.32.13.2 CAS Registry ID: 54037-14-8

(B) Boron Boron is a Group 13 element that has properties which are borderline between metals and non-metals (semi metallic). It is a semiconductor rather than a metallic conductor. Chemically it is closer to silicon than to aluminum, gallium, indium, and thallium. Crystalline boron is inert chemically and is resistant to attack by boiling HF or HCl. When finely divided it is attacked slowly by hot concentrated nitric acid.

Name: boron Symbol: B Atomic number: 5 Relative atomic mass (Ar): 10.811 (7) [see notes g m r] Standard state: solid at 298 K Color: black Classification: Semi-metallic Group in periodic table: 13 Group name: (none) Period in periodic table: 2 Block in periodic table: p-block Electron shell structure: 2.3 CAS Registry ID: 7440-42-8

(Br) Bromine Bromine is the only liquid nonmetallic element. It is a member of the halogen group. It is a heavy, volatile, mobile, dangerous reddish-brown liquid. The red vapor has a strong unpleasant odor and the vapor irritates the eyes and throat. It is a bleaching. When spilled on the skin it produces painful sores. It is a serious health hazard, and maximum safety precautions should be taken when handling it.

Name: bromine Symbol: Br Atomic number: 35 Relative atomic mass (Ar): 79.904 (1) Standard state: liquid at 298 K Color: red-brown, metallic luster when solid Classification: Non-metallic Group in periodic table: 17 Group name: Halogen Period in periodic table: 4 Block in periodic table: p-block Electron shell structure: 2.8.18.7 CAS Registry ID: 7726-95-6

(Cd) Cadmium Cadmium is a soft, bluish-white metal and is easily cut with a knife. It is similar in many respects to zinc. Interestingly, aa characteristic cadmium "scream" is heard on bending a cadmium bar (such as that illustrated above). Cadmium and its compounds are highly toxic. Silver solder, which contains cadmium, should be handled with care

Name: cadmium Symbol: Cd Atomic number: 48 Relative atomic mass (Ar): 112.411 (8) [see note g] Standard state: solid at 298 K Color: silvery grey metallic Classification: Metallic Group in periodic table: 12 Group name: (none) Period in periodic table: 5 Block in periodic table: d-block Electron shell structure: 2.8.18.18.2 CAS Registry ID: 7440-43-9

(Ca) Calcium Calcium as the element is a grey silvery metal. The metal is rather hard. Calcium is an essential constituent of leaves, bones, teeth, and shells. Calcium is the fifth most abundant element in the earth's crust and makes up more than 3% of the crust. Calcium does not occur as the metal itself in nature and instead is found in various minerals including as limestone, gypsum and fluorite. Stalagmites and stalactites contain calcium carbonate (CaCO3). Calcium carbonate is the basis of the cement industry. Calcium is classified chemically as one of the alkaline earth elements (that is, in Group 2 of the periodic table. The metal is rather reactive. It readily forms a white coating of calcium nitride (Ca3N2) in air. It reacts with water and the metal burns with a yellow-red flame, forming largely the nitride.

Name: calcium Symbol: Ca Atomic number: 20 Relative atomic mass (Ar): 40.078 (4) [see note g] Standard state: solid at 298 K Color: silvery white Classification: Metallic Group in periodic table: 2 Group name: Alkaline earth metal Period in periodic table: 4 Block in periodic table: s-block Electron shell structure: 2.8.8.2 CAS Registry ID: 7440-70-2

(C) Carbon Carbon is a Group 14 element and is distributed very widely in nature. It is found in abundance in the sun, stars, comets, and atmospheres of most planets. Carbon is present as carbon dioxide in the atmosphere and dissolved in all natural waters. It is a component of rocks as carbonates of calcium (limestone), magnesium, and iron. The atmosphere of Mars is very thin but what there is contains about 95 % CO2. Coal, petroleum, and natural gas are chiefly hydrocarbons. Carbon is unique among the elements in the vast number of variety of compounds it can form. Organic chemistry, a 1/112th subset of inorganic chemistry, is the study of carbon and its compounds. While silicon might take the place of carbon in forming a host of related compounds, it is not possible currently to form stable compounds with very long chains of silicon atoms. Carbon is found free in nature in three allotropic forms: amorphous, graphite, and diamond. Graphite is one of the softest known materials while diamond is one of the hardest. Carbon, as microscopic diamonds, is found in some meteorites. Natural diamonds are found in ancient volcanic "pipes" such as found in South Africa. Diamonds are also recovered from the ocean floor off the Cape of Good Hope.

Name: carbon Symbol: C Atomic number: 6 Relative atomic mass (Ar): 12.0107 (8) [see notes g r] Standard state: solid at 298 K Color: graphite is black, diamond is colorless Classification: Non-metallic Group in periodic table: 14 Group name: (none) Period in periodic table: 2 Block in periodic table: p-block Electron shell structure: 2.4 CAS Registry ID: 7440-44-0

(Cr) Chromium Chromium is steel-gray, lustrous, hard, metallic, and takes a high polish. Its compounds are toxic. It is found as chromite ore. Siberian red lead (crocoite, PrCrO4) is a chromium ore prized as a red pigment for oil paints. Emerald is a form of beryl (a beryllium aluminum silicate) which is green because of the inclusion of a little chromium into the beryl crystal lattice in place of some of the aluminum ions. Similarly, traces of chromium incorporated into the crystal lattice of corundum (crystalline aluminum oxide, Al2O3) as a replacement for some of the Al3+ ions results in another highly colored gem stone, in this case the red ruby.

Name: chromium Symbol: Cr Atomic number: 24 Relative atomic mass (Ar): 51.9961 (6) Standard state: solid at 298 K Color: silvery metallic Classification: Metallic Group in periodic table: 6 Group name: (none) Period in periodic table: 4 Block in periodic table: d-block Electron shell structure: 2.8.13.1 CAS Registry ID: 7440-47-3

(Co) Cobalt Cobalt is a brittle, hard, silver-grey transition metal with magnetic properties similar to those of iron (ferromagnetic). Cobalt is present in meteorites. Ore deposits are found in Zaire, Morocco and Canada. The isotope cobalt-60 (60Co) is an artificially produced isotope used as a source of γ rays (its high energy radiation is useful for sterilization in medicine and of foods). Cobalt salts color glass a beautiful deep blue color. Cobalt compounds are important catalysts in a number of industrial processes. Cobalt is required in small amounts for life and is the only metal found in vitamins (cobalt is the critical component of vitamin B12.

Name: cobalt Symbol: Co Atomic number: 27 Relative atomic mass (Ar): 58.933195 (5) Standard state: solid at 298 K Color: lustrous, metallic, grayish tinge Classification: Metallic Group in periodic table: 9 Group name: (none) Period in periodic table: 4 Block in periodic table: d-block Electron shell structure: 2.8.15.2 CAS Registry ID: 7440-48-4

(Cn) Copernicium Copernicium was discovered on 9th February 1996 at 22:37 at the GSI in Darmstadt, Germany. Further information on element 112 is here (outside WebElements) and here in a press release (outside WebElements). The interested reader should consult the on-line version of The Wonderful World of Atoms and Nuclei for a fascinating insight into research on "super-heavy" atoms.

Name: copernicium Symbol: Cn Atomic number: 112 Relative atomic mass (Ar): [ 285 ] Standard state: presumably a liquid at 298 K Color: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic Group in periodic table: 12 Group name: (none) Period in periodic table: 7 Block in periodic table: d-block Electron shell structure: 2.8.18.32.32.18.2 CAS Registry ID: 54084-26-3

(Cu) Copper Copper appears in the periodic table at the top of Group 11 above silver and gold. Collectively these are sometimes referred to as the coinage metals, although in modern times these metals are used less frequently than in the past. Copper is one of the most important metals. Copper is reddish with a bright metallic luster. It is malleable, ductile, and a good conductor of heat and electricity (second only to silver in electrical conductivity). Its alloys, brass and bronze, are very important. Monel and gun metals also contain copper. Apparently the reason that policemen in the USA are nicknamed "cops" or "coppers" is to do with their uniforms which used to have copper buttons. Copper metal is not particularly reactive and indeed is found as the free metal ("native") on occasion. Copper sulfate is [Cu(SO4)(OH2)4].H2O in the crystalline state; it is particularly well known and was often called blue vitriol. The oxidation number in most copper compounds is Cu(II), old name cupric, but there are many important Cu(I) compounds (cuprous) as well.

Name: copper Symbol: Cu Atomic number: 29 Relative atomic mass (Ar): 63.546 (3) [see note r] Standard state: solid at 298 K Color: copper, metallic Classification: Metallic Group in periodic table: 11 Group name: Coinage metal Period in periodic table: 4 Block in periodic table: d-block Electron shell structure: 2.8.18.1 CAS Registry ID: 7440-50-8

(Ds) Darmstadtium Darmstadtium, is a synthetic element that is not present in the environment at all. Further information on element 110 is here (outside WebElements) and in a press release (outside WebElements). The interested reader should consult the on-line version of The Wonderful World of Atoms and Nuclei for a fascinating insight into research on "super-heavy" atoms. Chemically, darmstadtium is in the same Group as nickel, palladium, and platinum (Group 10). Unlike these lighter atoms, darmstadtium decays after a small fraction of a thousandth of a second into lighter elements by emitting α-particles which are the nuclei of helium atoms.

Name: darmstadtium Symbol: Ds Atomic number: 110 Relative atomic mass (Ar): [ 281 ] Standard state: presumably a solid at 298 K Color: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic Group in periodic table: 10 Group name: (none) Period in periodic table: 7 Block in periodic table: d-block Electron shell structure: 2.8.18.32.32.17.1 CAS Registry ID: 54083-77-1

(Fl) Flerovium Flerovium was reported informally in January 1999 following experiments towards the end of December 1998 involving scientists at Dubna (Joint Institute for Nuclear Research) in Russia apparently using isotopes supplied by scientists at the Lawrence Livermore National Laboratory, USA. Only one atom was identified at that time and the claim only just been ratified. The results of calculations suggest that flerovium will not form a tetrafluoride FlF4, but could be isolated as a water-soluble difluoride FlF2.

Name: flerovium Symbol: Fl Atomic number: 114 Relative atomic mass (Ar): [ 289 ] Standard state: presumably a solid at 298 K Color: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic Group in periodic table: 14 Group name: (none) Period in periodic table: 7 Block in periodic table: p-block Electron shell structure: 2.8.18.32.32.18.4 CAS Registry ID: 54085-16-4

(F) Fluorine Fluorine is a Group 17 element. Fluorine is the most electronegative and reactive of all elements. It is a pale yellow, corrosive gas, which reacts with practically all organic and inorganic substances. Finely divided metals, glass, ceramics, carbon, and even water burn in fluorine with a bright flame. It is not uncommon to see fluorine spelled incorrectly as fluorine.

Name: fluorine Symbol: F Atomic number: 9 Relative atomic mass (Ar): 18.9984032 (5) Standard state: gas at 298 K Color: pale yellow Classification: Non-metallic Group in periodic table: 17 Group name: Halogen Period in periodic table: 2 Block in periodic table: p-block Electron shell structure: 2.7 CAS Registry ID: 7782-41-4

(Fr) Francium Francium occurs as a result of α disintegration of actinium. Francium is found in uranium minerals, and can be made artificially by bombarding thorium with protons. It is the most unstable of the first 101 elements. The longest lived isotope, 223Fr, a daughter of 227Ac, has a half-life of 22 minutes. This is the only isotope of francium occurring in nature, but at most there is only 20-30 g of the element present in the earth's crust at any one time. No weighable quantity of the element has been prepared or isolated. There are about 20 known isotopes.

Name: francium Symbol: Fr Atomic number: 87 Relative atomic mass (Ar): [ 223 ] Standard state: solid at 298 K Color: metallic Classification: Metallic Group in periodic table: 1 Group name: Alkali metal Period in periodic table: 7 Block in periodic table: s-block Electron shell structure: 2.8.18.32.18.8.1 CAS Registry ID: 7440-73-5

(Ga) Gallium Gallium is the only metal, except for mercury, caesium, and rubidium, which can be liquid near room temperatures; this makes possible its use in high-temperature thermometers. It has one of the longest liquid ranges of any metal and has a low vapor pressure even at high temperatures. Ultra-pure gallium has a beautiful, silvery appearance, and the solid metal exhibits a conchoidal fracture similar to glass. The metal expands on solidifying; therefore, it should not be stored in glass or metal containers, as they may break as the metal solidifies.

Name: gallium Symbol: Ga Atomic number: 31 Relative atomic mass (Ar): 69.723 (1) Standard state: solid at 298 K (but melts only slightly above this temperature) Color: silvery white Classification: Metallic Group in periodic table: 13 Group name: (none) Period in periodic table: 4 Block in periodic table: p-block Electron shell structure: 2.8.18.3 CAS Registry ID: 7440-55-3

(Ge) Germanium Germanium is a gray-white semi-metal, and in its pure state is crystalline and brittle, retaining its luster in air at room temperature. It is a very important semiconductor material. Zone-refining techniques have led to production of crystalline germanium for semiconductor use with an impurity of only one part in 10-10. Certain germanium compounds have a low mammalian toxicity, but a clear activity against certain bacteria, which makes them of interest as chemotherapeutic agents.

Name: germanium Symbol: Ge Atomic number: 32 Relative atomic mass (Ar): 72.64 (1) Standard state: solid at 298 K Color: grayish white Classification: Semi-metallic Group in periodic table: 14 Group name: (none) Period in periodic table: 4 Block in periodic table: p-block Electron shell structure: 2.8.18.4 CAS Registry ID: 7440-56-4

(Au) Gold Most metals are metallic grey or silvery white whereas gold is characteristically a metallic yellow color, in other words gold-colored. Caesium is also gold colored. The gold color seems related to relativistic effects of the outermost gold orbitals. Small amounts of other metals alloyed with gold change the color as well as mechanical properties such as hardness. White gold for jewelry is formed by mixing palladium, silver, or nickel with gold, although the result is green gold with certain proportions of silver. White gold is commonly used for wedding rings in the USA. Addition of some copper gives "rose gold", a soft pink color. Remarkably other colors such as purple (a gold:aluminum alloy), blue (a gold:indium alloy) and even black (a gold:cobalt alloy) may be formed. Gold is usually alloyed in jewelry to give it more strength, and the term carat describes the amount of gold present (24 carats is pure gold). It is estimated that all the gold in the world, so far refined, could be placed in a single cube 60 ft. on a side. It is metallic, with a yellow color when in a mass, but when finely divided it may be black, ruby, or purple.

Name: gold Symbol: Au Atomic number: 79 Relative atomic mass (Ar): 196.966569 (4) Standard state: solid at 298 K Color: gold Classification: Metallic Group in periodic table: 11 Group name: Coinage metal Period in periodic table: 6 Block in periodic table: d-block Electron shell structure: 2.8.18.32.18.1 CAS Registry ID: 7440-57-5

(Hf) Hafnium Most zirconium minerals contain 1 to 3% hafnium. Hafnium is a ductile metal with a brilliant silver luster. Its properties are influenced considerably by the impurities of zirconium present. Of all the elements, zirconium and hafnium are two of the most difficult to separate. Hafnium is a Group 4 transition element. Because hafnium has a good absorption cross section for thermal neutrons (almost 600 times that of zirconium), has excellent mechanical properties, and is extremely corrosion resistant, it is used for nuclear reactor control rods. Hafnium carbide is the most refractory binary composition known, and the nitride is the most refractory metal nitride (m.p. 3310°C).

Name: hafnium Symbol: Hf Atomic number: 72 Relative atomic mass (Ar): 178.49 (2) Standard state: solid at 298 K Color: grey steel Classification: Metallic Group in periodic table: 4 Group name: (none) Period in periodic table: 6 Block in periodic table: d-block Electron shell structure: 2.8.18.32.10.2 CAS Registry ID: 7440-58-6

(Hs) Hassium Hassium, is a synthetic element that is not present in the environment at all. The interested reader should consult the on-line version of The Wonderful World of Atoms and Nuclei for a fascinating insight into research on "super-heavy" atoms.

Name: hassium Symbol: Hs Atomic number: 108 Relative atomic mass (Ar): [ 277 ] (status unclear) Standard state: presumably a solid at 298 K Color: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic Group in periodic table: 8 Group name: (none) Period in periodic table: 7 Block in periodic table: d-block Electron shell structure: 2.8.18.32.32.14.2 CAS Registry ID: 54037-57-9

(He) Helium Helium is one of the so-called noble gases. Helium gas is an un-reactive, colorless, and odorless monoatomic gas. Helium is available in pressurized tanks. Helium is the second most abundant element in the universe after hydrogen. α-particles are doubly ionized helium atoms, He2+. Helium is used in lighter than air balloons and while heavier than hydrogen, is far safer since helium does not burn. Speaking after breathing an atmosphere rich in helium results in a squeaky voice (don't try it!). Helium is present in the atmosphere at about 0.0005% (1 part in 200000) by volume and is an important component within hydrocarbon gases in the USA. Its origin in these gases is traced to the decay of radioactive elements in rocks.

Name: helium Symbol: He Atomic number: 2 Relative atomic mass (Ar): 4.002602 (2) [see notes g r] Standard state: gas at 298 K Colour: colorless Classification: Non-metallic Group in periodic table: 18 Group name: Noble gas Period in periodic table: 1 Block in periodic table: p-block Electron shell structure: 2 CAS Registry ID: 7440-59-7

(H) Hydrogen Hydrogen is the lightest element. It is by far the most abundant element in the universe and makes up about about 90% of the universe by weight. It is also the most abundant element in the earth's sun. Hydrogen as water (H2O) is absolutely essential to life and it is present in all organic compounds. Hydrogen is the lightest gas. Hydrogen gas was used in lighter-than-air balloons for transport but is far too dangerous because of the fire risk (Hindenburg). It burns in air to form only water as waste product and if hydrogen could be made on sufficient scale from other than fossil fuels then there might be a possibility of a hydrogen economy.

Name: hydrogen Symbol: H Atomic number: 1 Relative atomic mass (Ar): 1.00794 (7) [see notes g m r] Standard state: gas at 298 K Colour: colorless Classification: Non-metallic Group in periodic table: 1 Group name: (none) Period in periodic table: 1 Block in periodic table: s-block Electron shell structure: 1 CAS Registry ID: 1333-74-0

(In) Indium Indium is a very soft, silvery-white metal with a brilliant luster. The pure metal gives a high-pitched "scream" when bent. It wets glass, as does gallium. It is useful for making low-melting alloys. An alloy of 24% indium and 76% gallium is liquid at room temperature. Canada produces the majority of of the world's supply of indium.

Name: indium Symbol: In Atomic number: 49 Relative atomic mass (Ar): 114.818 (3) Standard state: solid at 298 K Color: silvery lustrous grey Classification: Metallic Group in periodic table: 13 Group name: (none) Period in periodic table: 5 Block in periodic table: p-block Electron shell structure: 2.8.18.18.3 CAS Registry ID: 7440-74-6

(Ir) Iridium Ruthenium, rhodium, palladium, osmium, iridium, and platinum together make up a group of elements referred to as the platinum group metals (PGM). The name iridium is appropriate, for its salts are highly colored. Iridium is white, similar to platinum, but with a slight yellowish cast. It is very hard and brittle, making it very hard to machine, form, or work. It is the most corrosion resistant metal known, and was used in making the standard meter bar of Paris, which is a 90% platinum-10% iridium alloy. This meter bar has since been replaced as a fundamental unit of length (see Krypton). Iridium is not attacked by any of the acids nor by aqua regia, but is attacked by molten salts, such as NaCl and NaCN.

Name: iridium Symbol: Ir Atomic number: 77 Relative atomic mass (Ar): 192.217 (3) Standard state: solid at 298 K Color: silvery white Classification: Metallic Group in periodic table: 9 Group name: Precious metal or Platinum group metal Period in periodic table: 6 Block in periodic table: d-block Electron shell structure: 2.8.18.32.15.2 CAS Registry ID: 7439-88-5

(Fe) Iron Iron is a relatively abundant element in the universe. It is found in the sun and many types of stars in considerable quantity. Iron nuclei are very stable. Iron is a vital constituent of plant and animal life, and is the key component of hemoglobin. The pure metal is not often encountered in commerce, but is usually alloyed with carbon or other metals. The pure metal is very reactive chemically, and rapidly corrodes, especially in moist air or at elevated temperatures. Any car owner knows this. Iron metal is a silvery, lustrous metal which has important magnetic properties.

Name: iron Symbol: Fe Atomic number: 26 Relative atomic mass (Ar): 55.845 (2) Standard state: solid at 298 K Color: lustrous, metallic, grayish tinge Classification: Metallic Group in periodic table: 8 Group name: (none) Period in periodic table: 4 Block in periodic table: d-block Electron shell structure: 2.8.14.2 CAS Registry ID: 7439-89-6

(Mo) Molybdenum Molybdenum is a silvery-white, hard, transition metal. Scheele discovered it in 1778. It was often confused with graphite and lead ore. Molybdenum is used in alloys, electrodes and catalysts. The World War 2 German artillery piece called "Big Bertha" contains molybdenum as an essential component of its steel.

Name: molybdenum Symbol: Mo Atomic number: 42 Relative atomic mass (Ar): 95.96 (2) [see note g] Standard state: solid at 298 K Color: grey metallic Classification: Metallic Group in periodic table: 6 Group name: (none) Period in periodic table: 5 Block in periodic table: d-block Electron shell structure: 2.8.18.13.1 CAS Registry ID: 7439-98-7

(Kr) Krypton Krypton is present in the air at about 1 ppm. The atmosphere of Mars contains a little (about 0.3 ppm) of krypton. It is characterized by its brilliant green and orange spectral lines. The spectral lines of krypton are easily produced and some are very sharp. In 1960 it was internationally agreed that the fundamental unit of length, the meter, should be defined as 1 m = 1,650,763.73 wavelengths (in vacuo) of the orange-red line of Kr-33. Under normal conditions krypton is colorless, odorless, fairly expensive gas. Solid krypton is a white crystalline substance with a face-centered cubic structure which is common to all the "rare gases". Krypton difluoride, KrF2, has been prepared in gram quantities and can be made by several methods.

Name: krypton Symbol: Kr Atomic number: 36 Relative atomic mass (Ar): 83.798 (2) [see notes g m] Standard state: gas at 298 K Color: colorless Classification: Non-metallic Group in periodic table: 18 Group name: Noble gas Period in periodic table: 4 Block in periodic table: p-block Electron shell structure: 2.8.18.8 CAS Registry ID: 7439-90-9

(Lr) Lawrencium Lawrencium is a synthetic "rare earth metal" which does not occur in the environment.

Name: lawrencium Symbol: Lr Atomic number: 103 Relative atomic mass (Ar): [ 262 ] Standard state: presumably a solid at 298 K Color: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic Group in periodic table: 3 Group name: (none) Period in periodic table: 7 Block in periodic table: d-block Electron shell structure: 2.8.18.32.32.9.2 CAS Registry ID: 22537-19-5

(Pb) Lead Lead is a bluish-white lustrous metal. It is very soft, highly malleable, ductile, and a relatively poor conductor of electricity. It is very resistant to corrosion but tarnishes upon exposure to air. Lead pipes bearing the insignia of Roman emperors, used as drains from the baths, are still in service. Alloys include pewter and solder. Tetraethyl lead (PbEt4) is still used in some grades of petrol (gasoline) but is being phased out on environmental grounds. Lead isotopes are the end products of each of the three series of naturally occurring radioactive elements.

Name: lead Symbol: Pb Atomic number: 82 Relative atomic mass (Ar): 207.2 (1) [see notes g m] Standard state: solid at 298 K Color: bluish white Classification: Metallic Group in periodic table: 14 Group name: (none) Period in periodic table: 6 Block in periodic table: p-block Electron shell structure: 2.8.18.32.18.4 CAS Registry ID: 7439-92-1

(Li) Lithium Lithium is a Group 1 (IA) element containing just a single valence electron (1s22s1). Group 1 elements are called "alkali metals". Lithium is a solid only about half as dense as water and lithium metal is the least dense metal. A freshly cut chunk of lithium is silvery, but tarnishes in a minute or so in air to give a grey surface. Its chemistry is dominated by its tendency to lose an electron to form Li+. It is the first element within the second period. Lithium is mixed (alloyed) with aluminum and magnesium for light-weight alloys, and is also used in batteries, some greases, some glasses, and in medicine. Lithium does not occur as the free metal in nature because of its high reactivity. Deposits are known all around the world. It is a minor component of nearly all igneous rocks and is a component of many natural brines.

Name: lithium Symbol: Li Atomic number: 3 Relative atomic mass (Ar): [ 6.941 (2)] [see notes g m r] Standard state: solid at 298 K Color: silvery white/grey Classification: Metallic Group in periodic table: 1 Group name: Alkali metal Period in periodic table: 2 Block in periodic table: s-block Electron shell structure: 2.1 CAS Registry ID: 7439-93-2

(Lu) Lutetium Pure metallic lutetium has been isolated only in recent years and is one of the more difficult to prepare. It can be prepared by the reduction of anhydrous LuCl3 or LuF3 by an alkali or alkaline earth metal. The metal is silvery white and relatively stable in air. It is a rare earth metal and perhaps the most expensive of all rare elements. It is found in small amounts with all rare earth metals, and is very difficult to separate from other rare elements.

Name: lutetium Symbol: Lu Atomic number: 71 Relative atomic mass (Ar): 174.9668 (1) [see note g] Standard state: solid at 298 K Color: silvery white Classification: Metallic Group in periodic table: 3 Group name: (none) Period in periodic table: 6 Block in periodic table: d-block Electron shell structure: 2.8.18.32.9.2 CAS Registry ID: 7439-94-3

(Mg) Magnesium Magnesium is a grayish-white, fairly tough metal. Magnesium is the eighth most abundant element in the earth's crust although not found in it's elemental form. It is a Group 2 element (Group IIA in older labelling schemes). Group 2 elements are called alkaline earth metals. Magnesium metal burns with a very bright light. Magnesium is an important element for plant and animal life. Chlorophylls are porphyrins based upon magnesium. The adult human daily requirement of magnesium is about 0.3 g day-1.

Name: magnesium Symbol: Mg Atomic number: 12 Relative atomic mass (Ar): 24.3050 (6) Standard state: solid at 298 K Color: silvery white Classification: Metallic Group in periodic table: 2 Group name: Alkaline earth metal Period in periodic table: 3 Block in periodic table: s-block Electron shell structure: 2.8.2 CAS Registry ID: 7439-95-4

(Mn) Manganese Manganese metal is gray-white, resembling iron, but is harder and very brittle. The metal is reactive chemically, and decomposes cold water slowly. Manganese is widely distributed throughout the animal kingdom. It is an important trace element and may be essential for utilization of vitamin B. Manganese is present in quantity the floor of oceans. It is an important component of steel.

Name: manganese Symbol: Mn Atomic number: 25 Relative atomic mass (Ar): 54.938045 (5) Standard state: solid at 298 K Color: silvery metallic Classification: Metallic Group in periodic table: 7 Group name: (none) Period in periodic table: 4 Block in periodic table: d-block Electron shell structure: 2.8.13.2 CAS Registry ID: 7439-96-5

(Hg) Mercury Mercury is the only common metal liquid at ordinary temperatures. Mercury is sometimes called quicksilver. It rarely occurs free in nature and is found mainly in cinnabar ore (HgS) in Spain and Italy. It is a heavy, silvery-white liquid metal. It is a rather poor conductor of heat as compared with other metals but is a fair conductor of electricity. It alloys easily with many metals, such as gold, silver, and tin. These alloys are called amalgams. Its ease in amalgamating with gold is made use of in the recovery of gold from its ores.

Name: mercury Symbol: Hg Atomic number: 80 Relative atomic mass (Ar): 200.59 (2) Standard state: liquid at 298 K (the heaviest known elemental liquid) Color: silvery white Classification: Metallic Group in periodic table: 12 Group name: (none) Period in periodic table: 6 Block in periodic table: d-block Electron shell structure: 2.8.18.32.18.2 CAS Registry ID: 7439-97-6

(Ne) Neon Neon is a very inert element. Neon forms an unstable hydrate. In a vacuum discharge tube, neon glows reddish orange. Of all the rare gases, the discharge of neon is the most intense at ordinary voltages and currents. It is present in the atmosphere as 1 part in 65000. Liquid neon has over 40 times more refrigerating capacity than liquid helium, and more than 3 times that of liquid hydrogen.

Name: neon Symbol: Ne Atomic number: 10 Relative atomic mass (Ar): 20.1797 (6) [see notes g m] Standard state: gas at 298 K Color: colorless Classification: Non-metallic Group in periodic table: 18 Group name: Noble gas Period in periodic table: 2 Block in periodic table: p-block Electron shell structure: 2.8 CAS Registry ID: 7440-01-9

(Ni) Nickel Nickel is found as a constituent in most meteorites and often serves as one of the criteria for distinguishing a meteorite from other minerals. Iron meteorites, or siderites, may contain iron alloyed with from 5 to nearly 20% nickel. The USA 5-cent coin (whose nickname is "nickel") contains just 25% nickel. Nickel is a silvery white metal that takes on a high polish. It is hard, malleable, ductile, somewhat ferromagnetic, and a fair conductor of heat and electricity. Nickel carbonyl, [Ni(CO)4], is an extremely toxic gas and exposure should not exceed 0.007 mg M-3.

Name: nickel Symbol: Ni Atomic number: 28 Relative atomic mass (Ar): 58.6934 (4) Standard state: solid at 298 K Color: lustrous, metallic, silvery tinge Classification: Metallic Group in periodic table: 10 Group name: (none) Period in periodic table: 4 Block in periodic table: d-block Electron shell structure: 2.8.16.2 CAS Registry ID: 7440-02-0

(Nb) Niobium The name niobium was adopted officially by IUPAC in 1950, but a few commercial producers still like to refer to it as columbium. Niobium is a shiny, white, soft, and ductile metal, and takes on a bluish tinge when exposed to air at room temperatures for a long time. The metal starts to oxidize in air at high temperatures, and when handled hot must be done so under a protective atmosphere so as to minimize oxide production.

Name: niobium Symbol: Nb Atomic number: 41 Relative atomic mass (Ar): 92.90638 (2) Standard state: solid at 298 K Color: grey metallic Classification: Metallic Group in periodic table: 5 Group name: (none) Period in periodic table: 5 Block in periodic table: d-block Electron shell structure: 2.8.18.12.1 CAS Registry ID: 7440-03-1

(N) Nitrogen Nitrogen is a Group 15 element. Nitrogen makes up about 78% of the atmosphere by volume but the atmosphere of Mars contains less than 3% nitrogen. The element seemed so inert that Lavoisier named it azote, meaning "without life". However, its compounds are vital components of foods, fertilizers, and explosives. Nitrogen gas is colorless, odorless, and generally inert. As a liquid it is also colorless and odorless. When nitrogen is heated, it combines directly with magnesium, lithium, or calcium. When mixed with oxygen and subjected to electric sparks, it forms nitric oxide (NO) and then the dioxide (NO2). When heated under pressure with hydrogen in the presence of a suitable catalyst , ammonia forms (Haber process). Nitrogen is "fixed" from the atmosphere by bacteria in the roots of certain plants such as clover. Hence the usefulness of clover in crop rotation.

Name: nitrogen Symbol: N Atomic number: 7 Relative atomic mass (Ar): 14.0067 (2) [see notes g r] Standard state: gas at 298 K Color: colorless Classification: Non-metallic Group in periodic table: 15 Group name: Pnictogen Period in periodic table: 2 Block in periodic table: p-block Electron shell structure: 2.5 CAS Registry ID: 7727-37-9

(Os) Osmium Ruthenium, rhodium, palladium, osmium, iridium, and platinum together make up a group of elements referred to as the platinum group metals (PGM). Osmium metal is lustrous, bluish white, extremely hard, and brittle even at high temperatures. It has the highest melting point and lowest vapor pressure of the platinum group. The metal is very difficult to fabricate, but the powder can be sintered in a hydrogen atmosphere at a temperature of 2000°C. The solid metal is not affected by air at room temperature, but the powdered or spongy metal slowly gives off osmium tetroxide, which is a powerful oxidizing agent and has a strong smell. The tetroxide is highly toxic, and boils at 130°C (760 mm). Concentrations in air as low as 10-7 g m-3 can cause lung congestion, skin damage, or eye damage.

Name: osmium Symbol: Os Atomic number: 76 Relative atomic mass (Ar): 190.23 (3) [see note g] Standard state: solid at 298 K Color: bluish grey Classification: Metallic Group in periodic table: 8 Group name: Precious metal or Platinum group metal Period in periodic table: 6 Block in periodic table: d-block Electron shell structure: 2.8.18.32.14.2 CAS Registry ID: 7440-04-2

(O) Oxygen Oxygen is a Group 16 element. While about one fifth of the atmosphere is oxygen gas, the atmosphere of Mars contains only about 0.15% oxygen. Oxygen is the third most abundant element found in the sun, and it plays a part in the carbon-nitrogen cycle, one process responsible for stellar energy production. Oxygen in excited states is responsible for the bright red and yellow-green colors of the aurora. About two thirds of the human body, and nine tenths of water, is oxygen. The gas is colorless, odorless, and tasteless. Liquid and solid oxygen are pale blue (see picture above) and strongly paramagnetic (contains unpaired electrons).

Name: oxygen Symbol: O Atomic number: 8 Relative atomic mass (Ar): 15.9994 (3) [see notes g r] Standard state: gas at 298 K Color: colorless as a gas, liquid is pale blue Classification: Non-metallic Group in periodic table: 16 Group name: Chalcogen Period in periodic table: 2 Block in periodic table: p-block Electron shell structure: 2.6 CAS Registry ID: 7782-44-7

(Pd) Palladium Palladium is a steel-white metal, does not tarnish in air, and is the least dense and lowest melting of the platinum group metals. When annealed, it is soft and ductile. Cold working increases its strength and hardness. It is used in some watch springs. Ruthenium, rhodium, palladium, osmium, iridium, and platinum together make up a group of elements referred to as the platinum group metals (PGM). At room temperatures the metal has the unusual property of absorbing up to 900 times its own volume of hydrogen. Hydrogen readily diffuses through heated palladium and this provides a means of purifying the gas.

Name: palladium Symbol: Pd Atomic number: 46 Relative atomic mass (Ar): 106.42 (1) [see note g] Standard state: solid at 298 K Color: silvery white metallic Classification: Metallic Group in periodic table: 10 Group name: Precious metal or Platinum group metal Period in periodic table: 5 Block in periodic table: d-block Electron shell structure: 2.8.18.18.0 CAS Registry ID: 7440-05-3

(P) Phosphorus Phosphorus is commonly misspelled "phosphorous". It is an essential component of living systems and is found in nervous tissue, bones and cell protoplasm. Phosphorus exists in several allotropic forms including white (or yellow), red, and black (or violet). White phosphorus has two modifications. Ordinary phosphorus is a waxy white solid. When pure, it is colorless and transparent. It is insoluble in water, but soluble in carbon disulphide. It catches fire spontaneously in air, burning to P4O10, often misnamed as phosphorus pentoxide. When exposed to sunlight, or when heated in its own vapor to 250°C, it is converted to the red variety. This form does not ignite spontaneously and it is a little less dangerous than white phosphorus. The red modification is fairly stable and sublimes with a vapor pressure of 1 atmosphere at 417°C.

Name: phosphorus Symbol: P Atomic number: 15 Relative atomic mass (Ar): 30.973762 (2) Standard state: solid at 298 K Color: colorless/red/silvery white Classification: Non-metallic Group in periodic table: 15 Group name: Pnictogen Period in periodic table: 3 Block in periodic table: p-block Electron shell structure: 2.8.5 CAS Registry ID: 7723-14-0

(Pt) Platinum Ruthenium, rhodium, palladium, osmium, iridium, and platinum together make up a group of elements referred to as the platinum group metals (PGM). Platinum is a beautiful silvery-white metal, when pure, and is malleable and ductile. It has a coefficient of expansion almost equal to that of soda-lime-silica glass, and is therefore used to make sealed electrodes in glass systems. The metal does not oxidize in air. It is insoluble in hydrochloric and nitric acid, but dissolves when they are mixed as aqua regia, forming chloroplatinic acid (H2PtCl6), an important compound. It is corroded by halogens, cyanides, sulphur and alkalis. Hydrogen and oxygen gas mixtures explode in the presence of platinum wire.

Name: platinum Symbol: Pt Atomic number: 78 Relative atomic mass (Ar): 195.084 (9) Standard state: solid at 298 K Color: grayish white Classification: Metallic Group in periodic table: 10 Group name: Precious metal or platinum group metal Period in periodic table: 6 Block in periodic table: d-block Electron shell structure: 2.8.18.32.17.1 CAS Registry ID: 7440-06-4

(Po) Polonium Polonium has more isotopes than any other element, all of which are radioactive. Polonium dissolves readily in dilute acids, but is only slightly soluble in alkalis. Weight for weight it is about 2.5 x 1011 times as toxic as hydrocyanic acid (HCN). Polonium has been found in tobacco as a contaminant and in uranium ores.

Name: polonium Symbol: Po Atomic number: 84 Relative atomic mass (Ar): [ 209 ] Standard state: solid at 298 K Color: silvery Classification: Metallic Group in periodic table: 16 Group name: Chalcogen Period in periodic table: 6 Block in periodic table: p-block Electron shell structure: 2.8.18.32.18.6 CAS Registry ID: 7440-08-6

(K) Potassium Potassium is a metal and is the seventh most abundant and makes up about 1.5 % by weight of the earth's crust. Potassium is an essential constituent for plant growth and it is found in most soils. It is also a vital element in the human diet. Potassium is never found free in nature, but is obtained by electrolysis of the chloride or hydroxide, much in the same manner as prepared by Davy. It is one of the most reactive and electropositive of metals and, apart from lithium, it is the least dense known metal. It is soft and easily cut with a knife. It is silvery in appearance immediately after a fresh surface is exposed. It oxidizes very rapidly in air and must be stored under argon or under a suitable mineral oil. As do all the other metals of the alkali group, it decomposes in water with the evolution of hydrogen. It usually catches fire during the reaction with water. Potassium and its salts impart a lilac color to flames.

Name: potassium Symbol: K Atomic number: 19 Relative atomic mass (Ar): 39.0983 (1) Standard state: solid at 298 K Color: silvery white Classification: Metallic Group in periodic table: 1 Group name: Alkali metal Period in periodic table: 4 Block in periodic table: s-block Electron shell structure: 2.8.8.1 CAS Registry ID: 7440-09-7

(Ra) Radium Pure metallic radium is brilliant white when freshly prepared, but blackens on exposure to air, probably due to formation of the nitride. It exhibits luminescence, as do its salts; it decomposes in water and is somewhat more volatile than barium. Radium imparts a carmine red color to a flame.

Name: radium Symbol: Ra Atomic number: 88 Relative atomic mass (Ar): [ 226 ] Standard state: solid at 298 K Color: metallic Classification: Metallic Group in periodic table: 2 Group name: Alkaline earth metal Period in periodic table: 7 Block in periodic table: s-block Electron shell structure: 2.8.18.32.18.8.2 CAS Registry ID: 7440-14-4

(Rn) Radon At ordinary temperatures radon is a colorless gas. When cooled below the freezing point, radon exhibits a brilliant phosphorescence which becomes yellow as the temperature is lowered and orange-red at the temperature of liquid air. The main hazard is from inhalation of the element and its decay products which are collected on dust in the air. Recently, radon buildup in homes from the surrounding soil and rocks has become a safety issue and some areas around the world test homes for radon gas. It is the heaviest known gas. Radon is present in some spring waters.

Name: radon Symbol: Rn Atomic number: 86 Relative atomic mass (Ar): [ 222 ] Standard state: gas at 298 K (the heaviest known mononuclear gas at 298 K) Color: colorless Classification: Non-metallic Group in periodic table: 18 Group name: Noble gas Period in periodic table: 6 Block in periodic table: p-block Electron shell structure: 2.8.18.32.18.8 CAS Registry ID: 10043-92-2

(Re) Rhenium Rhenium is silvery white with a metallic luster; its density is exceeded only by that of platinum, iridium, and osmium, and its melting point is exceeded only by that of tungsten and carbon. It has other useful properties. It is expensive but useful as a trace alloying agent.

Name: rhenium Symbol: Re Atomic number: 75 Relative atomic mass (Ar): 186.207 (1) Standard state: solid at 298 K Color: grayish white Classification: Metallic Group in periodic table: 7 Group name: (none) Period in periodic table: 6 Block in periodic table: d-block Electron shell structure: 2.8.18.32.13.2 CAS Registry ID: 7440-15-5

(Rh) Rhodium Rhodium metal is silvery white. Rhodium has a higher melting point and lower density than platinum. It has a high reflectance and is hard and durable. Upon heating it turns to the oxide when red and at higher temperatures turns back to the element. It is a major component of industrial catalytic systems such as the BP-Monsanto process. Ruthenium, rhodium, palladium, osmium, iridium, and platinum together make up a group of elements referred to as the platinum group metals (PGM).

Name: rhodium Symbol: Rh Atomic number: 45 Relative atomic mass (Ar): 102.90550 (2) Standard state: solid at 298 K Color: silvery white metallic Classification: Metallic Group in periodic table: 9 Group name: Precious metal or Platinum group metal Period in periodic table: 5 Block in periodic table: d-block Electron shell structure: 2.8.18.16.1 CAS Registry ID: 7440-16-6

(Rg) Roentgenium Roentgenium, was discovered on 8th December 1994 at the GSI in Darmstadt, Germany. Further information on element 111 is here (outside WebElements). The information following is an abstract of this source. The interested reader should consult the on-line version of The Wonderful World of Atoms and Nuclei for a fascinating insight into research on "super-heavy" atoms.

Name: roentgenium Symbol: Rg Atomic number: 111 Relative atomic mass (Ar): [ 280 ] Standard state: presumably a solid at 298 K Color: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic Group in periodic table: 11 Group name: (none) Period in periodic table: 7 Block in periodic table: d-block Electron shell structure: 2.8.18.32.32.18.1 CAS Registry ID: 54386-24-2

(Rb) Rubidium Rubidium can be liquid at ambient temperature, but only on a hot day given that its melting point is about 40°C. It is a soft, silvery-white metallic element of the alkali metals group (Group 1). It is one of the most most electropositive and alkaline elements. It ignites spontaneously in air and reacts violently with water, setting fire to the liberated hydrogen. As so with all the other alkali metals, it forms amalgams with mercury. It alloys with gold, caesium, sodium, and potassium. It colors a flame yellowish-violet.

Name: rubidium Symbol: Rb Atomic number: 37 Relative atomic mass (Ar): 85.4678 (3) [see note g] Standard state: solid at 298 K Color: silvery white Classification: Metallic Group in periodic table: 1 Group name: Alkali metal Period in periodic table: 5 Block in periodic table: s-block Electron shell structure: 2.8.18.8.1 CAS Registry ID: 7440-17-7

(Ru) Ruthenium Ruthenium is a hard, white metal. It does not tarnish at room temperatures, but oxidizes in air at about 800°C. The metal is not attacked by hot or cold acids or aqua regia, but when potassium chlorate is added to the solution, it oxidizes explosively. Ruthenium, rhodium, palladium, osmium, iridium, and platinum together make up a group of elements referred to as the platinum group metals (PGM).

Name: ruthenium Symbol: Ru Atomic number: 44 Relative atomic mass (Ar): 101.07 (2) [see note g] Standard state: solid at 298 K Color: silvery white metallic Classification: Metallic Group in periodic table: 8 Group name: Precious metal or Platinum group metal Period in periodic table: 5 Block in periodic table: d-block Electron shell structure: 2.8.18.15.1 CAS Registry ID: 7440-18-8

(Rf) Rutherfordium Rutherfordium is a synthetic element that is not present in the environment at all. It has no uses.

Name: rutherfordium Symbol: Rf Atomic number: 104 Relative atomic mass (Ar): [ 265 ] Standard state: presumably a solid at 298 K Color: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic Group in periodic table: 4 Group name: (none) Period in periodic table: 7 Block in periodic table: d-block Electron shell structure: 2.8.18.32.32.10.2 CAS Registry ID: 53850-36-5

(Sc) Scandium Scandium is a silvery-white metal which develops a slightly yellowish or pinkish cast upon exposure to air. It is relatively soft, and resembles yttrium and the rare-earth metals more than it resembles aluminum or titanium. Scandium reacts rapidly with many acids. Scandium is apparently a much more abundant element in the sun and certain stars than on earth.

Name: scandium Symbol: Sc Atomic number: 21 Relative atomic mass (Ar): 44.955912 (6) Standard state: solid at 298 K Color: silvery white Classification: Metallic Group in periodic table: 3 Group name: (none) Period in periodic table: 4 Block in periodic table: d-block Electron shell structure: 2.8.9.2 CAS Registry ID: 7440-20-2

(Sg) Seaborgium Seaborgium is a synthetic element that is not present in the environment at all. It has no uses.

Name: seaborgium Symbol: Sg Atomic number: 106 Relative atomic mass (Ar): [ 271 ] Standard state: presumably a solid at 298 K Color: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic Group in periodic table: 6 Group name: (none) Period in periodic table: 7 Block in periodic table: d-block Electron shell structure: 2.8.18.32.32.12.2 CAS Registry ID: 54038-81-2

(Se) Selenium Selenium can be prepared with either an amorphous or crystalline structure. Crystalline monoclinic selenium is deep red; crystalline hexagonal selenium, the most stable variety, is a metallic grey (see picture above). Elemental selenium is relatively nontoxic and is considered to be an essential trace element. However, hydrogen selenide (H2Se) and other selenium compounds are extremely toxic, and resemble arsenic in their physiological reactions. Hydrogen selenide in a concentration of 1.5 ppm is intolerable to man. Selenium occurs in some soils in amounts sufficient to produce serious effects on animals feeding on plants such as locoweed (an American plant) grown in such soils.

Name: selenium Symbol: Se Atomic number: 34 Relative atomic mass (Ar): 78.96 (3) Standard state: solid at 298 K Color: grey, metallic luster Classification: Non-metallic Group in periodic table: 16 Group name: Chalcogen Period in periodic table: 4 Block in periodic table: p-block Electron shell structure: 2.8.18.6 CAS Registry ID: 7782-49-2

(Si) Silicon Silicon is present in the sun and stars and is a principal component of a class of meteorites known as aerolites. Silicon makes up 25.7% of the earth's crust by weight, and is the second most abundant element, exceeded only by oxygen. It is found largely as silicon oxides such as sand (silica), quartz, rock crystal, amethyst, agate, flint, jasper and opal. Silicon is found also in minerals such as asbestos, feldspar, clay and mica. Silicon is important in plant and animal life. Diatoms in both fresh and salt water extract silica from the water to use as a component of their cell walls. Silicon is an important ingredient in steel. Silicon carbide is one of the most important abrasives. Workers in environments where siliceous dust is breathed may develop a serious lung disease known as silicosis.

Name: silicon Symbol: Si Atomic number: 14 Relative atomic mass (Ar): 28.0855 (3) [see note r] Standard state: solid at 298 K Color: dark grey with a bluish tinge Classification: Semi-metallic Group in periodic table: 14 Group name: (none) Period in periodic table: 3 Block in periodic table: p-block Electron shell structure: 2.8.4 CAS Registry ID: 7440-21-3

(Tl) Thallium When freshly exposed to air, thallium exhibits a metallic luster, but soon develops a bluish-grey tinge, resembling lead in appearance. A heavy oxide builds up on thallium if left in air, and in the presence of water the hydroxide is formed. The metal is very soft and malleable. It can be cut with a knife. The element and its compounds are toxic and should be handled carefully. Thallium may cause cancer.

Name: thallium Symbol: Tl Atomic number: 81 Relative atomic mass (Ar): 204.3833 (2) Standard state: solid at 298 K Color: silvery white Classification: Metallic Group in periodic table: 13 Group name: (none) Period in periodic table: 6 Block in periodic table: p-block Electron shell structure: 2.8.18.32.18.3 CAS Registry ID: 7440-28-0

(Ag) Silver Silver is somewhat rare and expensive, although not as expensive as gold. Slag dumps in Asia Minor and on islands in the Aegean Sea indicate that man learned to separate silver from lead as early as 3000 B.C. Pure silver has a brilliant white metallic luster. It is a little harder than gold and is very ductile and malleable. Pure silver has the highest electrical and thermal conductivity of all metals, and possesses the lowest contact resistance. Silver iodide, AgI, is (or was?) used for causing clouds to produce rain. Silver is stable in pure air and water, but tarnishes when exposed to ozone, hydrogen sulphide, or air containing sulphur. It occurs in ores including argentite, lead, lead-zinc, copper and gold found in Mexico, Peru, and the USA.

Name: silver Symbol: Ag Atomic number: 47 Relative atomic mass (Ar): 107.8682 (2) [see note g] Standard state: solid at 298 K Color: silver Classification: Metallic Group in periodic table: 11 Group name: Coinage metal Period in periodic table: 5 Block in periodic table: d-block Electron shell structure: 2.8.18.18.1 CAS Registry ID: 7440-22-4

(Na) Sodium Sodium is a Group 1 element (or IA in older labelling styles). Group 1 elements are often referred to as the "alkali metals". The chemistry of sodium is dominated by the +1 ion Na+. Sodium salts impart a characteristic orange/yellow color to flames and orange street lighting is orange because of the presence of sodium in the lamp. Soap is generally a sodium salt of fatty acids. The importance of common salt to animal nutrition has been recognized since prehistoric times. The most common compound is sodium chloride, (table salt).

Name: sodium Symbol: Na Atomic number: 11 Relative atomic mass (Ar): 22.98976928 (2) Standard state: solid at 298 K Color: silvery white Classification: Metallic Group in periodic table: 1 Group name: Alkali metal Period in periodic table: 3 Block in periodic table: s-block Electron shell structure: 2.8.1 CAS Registry ID: 7440-23-5

(Sr) Strontium Strontium does not occur as the free element. Strontium is softer than calcium and decomposes water more vigorously. Freshly cut strontium has a silvery appearance, but rapidly turns a yellowish color with the formation of the oxide. The finely divided metal ignites spontaneously in air. Volatile strontium salts impart an excellent crimson color to flames, and these salts are used in pyrotechnics.

Name: strontium Symbol: Sr Atomic number: 38 Relative atomic mass (Ar): 87.62 (1) [see notes g r] Standard state: solid at 298 K Color: silvery white Classification: Metallic Group in periodic table: 2 Group name: Alkaline earth metal Period in periodic table: 5 Block in periodic table: s-block Electron shell structure: 2.8.18.8.2 CAS Registry ID: 7440-24-6

(S) Sulfur Sulphur (sulfur) is a pale yellow, odorless, brittle solid, which is insoluble in water but soluble in carbon disulphide. Sulphur is essential to life. It is a minor constituent of fats, body fluids, and skeletal minerals. The spelling of sulphur is "sulfur" in the USA while sulphur is common elsewhere. IUPAC has does not have jurisdiction over language but has decided sulfur is preferred. Sulphur is found in meteorites, volcanoes, hot springs, and as galena, gypsum, Epsom salts, and barite. It is recovered commercially from "salt domes" along the Gulf Coast of the USA. Jupiter's moon Io owes its colors to various forms of sulphur. A dark area near the crater Aristarchus on the moon may be a sulphur deposit. Carbon disulphide, hydrogen sulphide, and sulphur dioxide should be handled extremely carefully. Hydrogen sulphide in very small concentrations can be metabolized, but in higher concentrations it can cause death quickly by respiratory paralysis. It is insidious in that it quickly deadens the sense of smell. Sulphur dioxide is a dangerous component in atmospheric air pollution and is one of the factors responsible for acid rain.

Name: sulfur Symbol: S Atomic number: 16 Relative atomic mass (Ar): 32.065 (5) [see notes g r] Standard state: solid at 298 K Color: lemon yellow Classification: Non-metallic Group in periodic table: 16 Group name: Chalcogen Period in periodic table: 3 Block in periodic table: p-block Electron shell structure: 2.8.6 CAS Registry ID: 7704-34-9

(Ta) Tantalum Tantalum is a grayish silver, heavy, and very hard metal. When pure, it is ductile and can be drawn into fine wire, which can be used as a filament for evaporating metals such as aluminum. Tantalum is almost completely immune to chemical attack at temperatures below 150°C, and is attacked only by hydrofluoric acid, acidic solutions containing the fluoride ion, and free sulphur trioxide. The element has a melting point exceeded only by tungsten and rhenium.

Name: tantalum Symbol: Ta Atomic number: 73 Relative atomic mass (Ar): 180.94788 (2) Standard state: solid at 298 K Color: grey blue Classification: Metallic Group in periodic table: 5 Group name: (none) Period in periodic table: 6 Block in periodic table: d-block Electron shell structure: 2.8.18.32.11.2 CAS Registry ID: 7440-25-7

(Tc) Technetium Since its discovery, searches for the element technetium in terrestrial materials have been made without success. Technetium has been found in the spectrum of S-, M-, and N-type stars, and its presence in stellar matter is leading to new theories of the production of heavy elements in the stars. Technetium is a silvery-grey metal that tarnishes slowly in moist air. Until 1960, technetium was available only in small amounts. The chemistry of technetium is related to that of rhenium.

Name: technetium Symbol: Tc Atomic number: 43 Relative atomic mass (Ar): [ 98 ] Standard state: solid at 298 K Color: silvery grey metallic Classification: Metallic Group in periodic table: 7 Group name: (none) Period in periodic table: 5 Block in periodic table: d-block Electron shell structure: 2.8.18.14.1 CAS Registry ID: 7440-26-8

(Te) Tellurium Crystalline tellurium has a silvery-white appearance, and exhibits a metallic luster when pure (see above). It is brittle and easily pulverized. Tellurium is a p-type semiconductor, and shows varying conductivity with crystal alignment. Its conductivity increases slightly with exposure to light. It can be doped with silver, copper, gold, tin, or other elements. Humans exposed to as little as 0.01 mg m-3 in air, or less, develop "tellurium breath", which has a garlic-like odor.

Name: tellurium Symbol: Te Atomic number: 52 Relative atomic mass (Ar): 127.60 (3) [see note g] Standard state: solid at 298 K Color: silvery lustrous grey Classification: Semi-metallic Group in periodic table: 16 Group name: Chalcogen Period in periodic table: 5 Block in periodic table: p-block Electron shell structure: 2.8.18.18.6 CAS Registry ID: 13494-80-9

(Ti) Titanium Titanium s a lustrous, white metal when pure. Titanium minerals are quite common. The metal has a low density, good strength, is easily fabricated, and has excellent corrosion resistance. The metal burns in air and is the only element that burns in nitrogen. It is marvelous in fireworks. Titanium is resistant to dilute sulphuric and hydrochloric acid, most organic acids, damp chlorine gas, and chloride solutions. Titanium metal is considered to be physiologically inert. Titanium is present in meteorites and in the sun. Some lunar rocks contain high concentrations of the dioxide, TiO2. Titanium oxide bands are prominent in the spectra of M-type stars.

Name: titanium Symbol: Ti Atomic number: 22 Relative atomic mass (Ar): 47.867 (1) Standard state: solid at 298 K Color: silvery metallic Classification: Metallic Group in periodic table: 4 Group name: (none) Period in periodic table: 4 Block in periodic table: d-block Electron shell structure: 2.8.10.2 CAS Registry ID: 7440-32-6

(Uup) Ununpentium On 10 September 2013 a paper published in Phys. Rev. Lett by D. Rudolph and others outlines additional evidence for the claims that fusion-evaporation reactions between 48Ca and 243Am ions lead to the 288Uup (288115) and 287Uup (287115). A total of thirty correlated α-decay chains were observed following the reactions.

Name: ununpentium Symbol: Uup Atomic number: 115 Relative atomic mass (Ar): [ 288 ] Standard state: presumably a solid at 298 K Color: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic Group in periodic table: 15 Group name: Pnictogen Period in periodic table: 7 Block in periodic table: p-block Electron shell structure: 2.8.18.32.32.18.5 CAS Registry ID: 54085-64-2

(Uus) Ununseptium

Name: ununseptium Symbol: Uus Atomic number: 117 Relative atomic mass (Ar): [ 294 ] Standard state: presumably a solid at 298 K Color: unknown, but probably metallic and dark in appearance Classification: Unknown Group in periodic table: 17 Group name: Halogen Period in periodic table: 7 Block in periodic table: p-block Electron shell structure: 2.8.18.32.32.18.7 CAS Registry ID: 87658-56-8

(Uut) Ununtrium On 12 August 2013 experiments involving zinc ions traveling at 10% of the speed of light colliding with a thin bismuth layer apparently produced a very heavy ion followed by a chain of six consecutive alpha decays identified as products of an isotope of element 113 278Uut - see new evidence for elements 113.

Name: ununtrium Symbol: Uut Atomic number: 113 Relative atomic mass (Ar): [ 284 ] Standard state: presumably a solid at 298 K Color: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic Group in periodic table: 13 Group name: (none) Period in periodic table: 7 Block in periodic table: p-block Electron shell structure: 2.8.18.32.32.18.3 CAS Registry ID: 54084-70-7

(V) Vanadium Pure vanadium is a grayish silvery metal, and is soft and ductile. It has good corrosion resistance to alkalis, sulphuric acid, hydrochloric acid, and salt waters. The metal oxidizes readily above 660°C to form V2O5. Industrially, most vanadium produced is used as an additive to improve steels.

Name: vanadium Symbol: V Atomic number: 23 Relative atomic mass (Ar): 50.9415 (1) Standard state: solid at 298 K Color: silvery grey metallic Classification: Metallic Group in periodic table: 5 Group name: (none) Period in periodic table: 4 Block in periodic table: d-block Electron shell structure: 2.8.11.2 CAS Registry ID: 7440-62-2

(Y) Yttrium Yttrium has a silvery-metallic luster. Yttrium turnings ignite in air. Yttrium is found in most rare-earth minerals. Moon rocks contain yttrium and yttrium is used as a "phosphor" to produce the red color in television screens.

Name: yttrium Symbol: Y Atomic number: 39 Relative atomic mass (Ar): 88.90585 (2) Standard state: solid at 298 K Color: silvery white Classification: Metallic Group in periodic table: 3 Group name: (none) Period in periodic table: 5 Block in periodic table: d-block Electron shell structure: 2.8.18.9.2 CAS Registry ID: 7440-65-5

(Zn) Zinc Zinc-deficient animals require 50% more food to gain the same weight of an animal supplied with adequate amounts of zinc. Zinc is not particularly toxic and is an essential element in the growth of all animals and plants. Plating thin layers of zinc on to iron or steel is known as galvanizing and helps to protect the iron from corrosion.

Name: zinc Symbol: Zn Atomic number: 30 Relative atomic mass (Ar): 65.38 (2) [see note g] Standard state: solid at 298 K Color: bluish pale grey Classification: Metallic Group in periodic table: 12 Group name: (none) Period in periodic table: 4 Block in periodic table: d-block Electron shell structure: 2.8.18.2 CAS Registry ID: 7440-66-6