The transition elements or transition metals occupy the short columns in the center of the periodic table, between Group 2A and Group 3A. They are sometimes called the d-block elements, since in this region the d-orbitals are being filled in, and are also referred to as B-group elements since in most numbering systems of the columns on the periodic table the numerals of these groups are followed by the letter B. The period 4 transition metals are scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn). The period 5 transition metals are yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), and cadmium (Cd). The period 6 transition metals are lanthanum (La), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), and mercury (Hg). The period 7 transition metals are the naturally-occurring actinium (Ac), and the artificially produced elements rutherfordium (Rf), dubnium (Db), seaborgium (Sg), bohrium (Bh), hassium (Hs), meitnerium (Mt), darmstadtium (Ds), roentgenium (Rg), and the as-yet unnamed ununbiium (Uub).
The elements which follow lanthanum (Z=57) and actinium (Z=89) are called the lanthanides and actinides, respectively, and together are known as the inner transition elements.
In the transition metals, the five d orbitals are being filled in, and the elements in general have electron configurations of (n-1)d1-10 ns2, although there are some exceptions when electrons are shuffled around to produce half-filled or filled d subshells. Many of the transition metals can lose two or three electrons, forming cations with charges of 2+ or 3+, but there are some which form 1+ charges, and some which form much higher charges.
All of the transition metals in their elemental forms are malleable and ductile (except for mercury, which is a liquid at room temperature), and are good conductors of heat and electricity. Many of the transition metal ions have characteristic colors associated with them, and many have biological and industrial significance.
Group 3B (3)
The Group 3B elements (Group 3 in the IUPAC designation) usually have electron configuration (n-1)d1 ns2. In most periodic tables, lanthanum and actinium are considered to be a part of Group 3B, but in others lanthanum and actinium are considered part of the inner transition elements, leaving lutetium and lawrencium in Group 3B instead. Most of these elements form 3+ charges, although other oxidation states are known.
Scandium (Sc, Z=21)
Scandium is a soft, silvery metal. It is named from the Latin word for Scandinavia, Scandia. It is found in the Earth's crust at a concentration of 16 ppm, making it the 35th most abundant element. It is found in the ore thortveitite [Sc2Si2O7], and is present in small amounts in other ores.
Scandium is lightweight, resistant to corrosion, and even stronger than aluminum, but its rarity makes its production costly. Scandium's existence was predicted by Dimitri Mendeleev from a gap in his periodic table of the elements; when scandium was discovered in 1879, its properties were close to those predicted by Mendeleev. There are few known compounds of scandium. Scandium iodide, ScI3, is used in mercury vapor lamps to produce a light that is closer to that of natural sunlight.
Yttrium (Y, Z=39)
Yttrium is a soft, silvery, ductile metal. The name is derived from the village of Ytterby, Sweden, where its ore was first isolated. (The same village has also given its name to the elements ytterbium, erbium, and terbium.) It is found in the Earth's crust at a concentration of 30 ppm, making it the 29th most abundant element. It is found in the ore xenotime [ytrium phosphate, YPO4], monazite [(Ce,La,Th,Nd,Y)PO4], bastnasite [(Ce,La,Y)CO3F], and in trace amounts in other minerals.
Yttrium is used in the phosphors that make the red elements of cathode-ray tube (CRT) televisions and computer monitors, and is also used to make white light-emitting diodes (LEDs). Yttrium is also used in some metal alloys. Yttrium is also a component of some of the "high-temperature superconductors" which conduct electricity with no resistance at temperatures below 90K (which can be accomplished by immersing the material in liquid nitrogen). The radioactive isotope yttrium-90, is used in the treatment of some cancers.
Lanthanum (La, Z=57)
Lanthanum is a soft, silvery-white, malleable, ductile, relatively reactive metal. The name is derived from the Greek word lanthanein, "to be hidden," because the element was discovered "hidden" as an impurity in ores of cerium. It is found in the Earth's crust at a concentration of 32 ppm, making it the 28th most abundant element. It is found in monazite and monazite sand [(Ce,La,Th,Nd,Y)PO4], bastnasite [(Ce,La,Y)CO3F], and in trace amounts in other minerals.
Lanthanum is used to make electrodes for high-intensity carbon arc lights, which are used for searchlights and projectors in movie theaters. Lanthanum salts are used to remove excess phosphate from patients who suffer from chronic kidney dysfunction. An alloy of lanthanum and nickel, when formed into a powder, is capable of absorbing 400 times its own volume of hydrogen gas, and is being investigated as a possible storage medium in hydrogen-powered vehicles.
The elements which follow lanthanum (atomic numbers 58-71), are known as the lanthanides; they are chemically similar to each other, and are often found together in various combination in ores.
Actinium (Ac, Z=89).
Actinium is a silvery-white, radioactive metal, which glows with blue light in the dark. Its name comes from the Greek word aktinos, meaning "ray." It is found only in trace amounts in the Earth's crust, and is one of the 10 least abundant elements. It is produced in the decay sequences of radioactive uranium-235. The most stable isotope of actinium is actinium-227, which has a half-life of 22.6 years, decaying by beta emission to produce thorium-227.
The elements which follow actinium (atomic numbers 90-103), are known as the actinides; these elements are all radioactive, and most of them are synthetic.
Group 4B (4)
The Group 4B elements (Group 4 in the IUPAC designation) usually have electron configuration (n-1)d2 ns2. Most of them form 4+ charges, although other oxidation states are known.
Titanium (Ti, Z=22)
Titanium is a hard, strong, silvery metal. The name is derived from the Titans of Greek mythology. It is found in the Earth's crust at a concentration of 4400 ppm, making it the 9th most abundant element. The most common ores of titanium are rutile (TiO2, the eighth most common compound on Earth) and ilmenite [FeTiO3].
Titanium melts at 1668°C, has a low density (4.51 g/cm3), and is as strong as steel, but is 45% lighter: this makes it an ideal metal for use in the aerospace industry. It is used in many applications where both strength and lightness are desirable, such as aircraft frames and engines, bicycles, and golf clubs. Titanium alloyed with aluminum and vanadium forms a metal with a higher strength-to-weight ratio than any other metal.
Titanium is resistant to corrosion because its surface becomes coated with a thin, hard oxide film, which is very resistant to further chemical attack. For this reason, titanium can be used in many medical devices. Titanium is used in the pins that hold broken bones together, and in cranial plates; it is a component in hip and knee replacements; and is used in pacemakers and surgical screws. Tissues bond to a titanium oxide layer on the surface of the metal which is formed when the metal is exposed to a plasma arc that exposes a fresh surface of titanium. Titanium's unreactivity also makes it useful in offshore oil rigs, and parts of ships that are exposed to seawater.
Titanium dioxide, TiO2, is commonly used in paints because of its intensely white color. (Since titanium compounds are nontoxic, its use has largely replacing that of lead in paints.) It is also used in sunscreens to scatter away ultraviolet light before it burns the skin. Titanium tetrachloride, TiCl4, reacts with moisture in the air to produce titanium dioxide and hydrochloric acid, generating a dense white vapor; it is used in skywriting and smoke-screen devices.
Zirconium (Zr, Z=40)
Zirconium is a tough, silvery, corrosion-resistant metal. Like titanium, zirconium metal resists corrosion because it easily forms a tough oxide coating. The name is derived from the Arabic word zargun, "gold colored." It is very difficult to separate zirconium from hafnium (which is right under zirconium on the periodic table) because the chemical properties of the two elements are very similar. It is found in the Earth's crust at a concentration of 190 ppm, making it the 18th most abundant element. The most common ores of zirconium are the gemstone zircon [ZrSiO4] and baddeleyite [ZrO2].
Zirconium metal is used inside nuclear reactors because it has such a high melting point (1855 °C), and because it does not capture neutrons to thereby form radioactive isotopes. Powered zirconium metal is very flammable, and is used in some military incendiary devices (such as Dragon's breath).
Zirconium oxide, or zirconia, ZrO2, melts at 2715°C, and is used in many high temperature applications, such as crucibles, ceramics, and some glasses. "Cubic zirconium" is a crystalline form of zirconium oxide commonly used in jewelry because its cubic crystal structure and high index of refraction gives it an appearance similar to diamond.
Hafnium (Hf, Z=72)
Hafnium is a silvery, corrosion-resistant metal. Like titanium and zirconium, it forms a highly corrosion-resistant oxide coating. The name comes from the Latin name for Copenhagen, Hafnia, the home of the Danish physicist Niels Bohr, who had suggested the arrangement of the outer electrons of the as-yet-unknown element. It is found in the Earth's crust at a concentration of 3.3 ppm, making it the 45th most abundant element. It is found in the ores hafnon [hafnium silicate, HfSiO4] and alvite [(Hf,Th,Zr)SiO4], and is obtained as a byproduct of zirconium refining.
Hafnium is chemically very similar to zirconium (see above), and is often present as an impurity in zirconium metals. Part of the reason for their chemical similarity is the fact that they are nearly the same size: zirconium has an atomic radius of 160 pm, while hafnium has a radius of 159 pm. Hafnium is used in control rods for nuclear power plants because of its ability to absorb thermal neutrons. It is also used in alloys with other metals, and in some ceramics.
Some hafnium compounds have the highest melting points of any binary compounds: hafnium carbide, HfC, melts at 3890°C, and hafnium nitride, HfN, melts at 3395°C.
Rutherfordium (Rf, Z=104).
Rutherfordium is a synthetic element, produced by the bombardment of californium-249 with carbon-12, or curium-248 with oxygen-18. The longest-lived isotope, rutherfordium-261, has a half-life of 65 seconds, so it's rather doubtful that we'll be building anything out of rutherfordium. The element is named after the physicist Ernest Rutherford. This element remained unnamed for a long time, because of a priority dispute between researchers at the Joint Institute for Nuclear Research (JINR) at Dubna (at the time, in the U.S.S.R.), and the University of California, Berkeley (U.S.A.); the name "rutherfordium" was finally approved by the International Union of Pure and Applied Chemistry (IUPAC) in 1997.
Group 5B (5)
The Group 5B elements (Group 5 in the IUPAC designation) usually have electron configuration of (n-1)d3 ns2.
Vanadium (V, Z=23)
Vanadium is a soft, ductile, silvery-white metal. Like many of the transition metals, the metal is resistant to corrosion because it forms a strong oxide coating; however, it does oxidize more readily at high temperatures. It is named for the Scandinavian goddess of beauty, Vanadis (Freya in Norse mythology), because of the variety of colored salts it forms. It is found in the Earth's crust at a concentration of 160 ppm, making it the 19th most abundant element. The principal ores of vanadium are vanadite [lead chloride vanadate, Pb5(VO4)3Cl], patronite [vanadium sulfide, VS4] and carnotite [potassium uranyl vanadate, K2(UO2)2(VO4)2·3H2O]. It is usually obtained as a byproduct from the processing of other ores.
One of the most common uses of vanadium metal is in alloys with iron, which is referred to as ferrovanadium, a strong, relatively lightweight, shock-resistant metal that is very resistant to corrosion. It is used in springs, high-speed tools, surgical instruments, gears and crankshafts, and armor plating. Traces of vanadium are also present in Damascus steel, which was prized for its hardness and ability to keep a sharp edge. When alloyed with aluminum and titanium, it is used in jet engines and airframes.
Vanadium forms a number of different cations — 2+, 3+, 4+, and 5+ — , and can be found in a large number of compounds.
Vanadium is a component in some enzymes. In some species of nitrogen-fixing bacteria, the iron-sulfur protein nitrogenase that is responsible for the "fixing" of nitrogen (its reduction from N2 to NH3), incorporates a vanadium ion, instead of the more typical molybdenum ion.
Niobium (Nb, Z=41)
Niobium is a shiny gray, soft, ductile metal. It is named after the Greek mythological character Niobe, daughter of Tantalus, because of the similarity of niobium to tantalum (see below). It is found in the Earth's crust at a concentration of 20 ppm, making it the 33rd most abundant element. It is found in the ores columbite [(Fe,Mn)(Nb,Ta)2O6], pyrochlore [(Na,Ca)2Nb2O6(OH,F)], and euxenite [(Y,Ca,Ce,U,Th)(Nb,Ta,Ti)2O6]. Tantalum is frequently found in trace amounts in niobium ores.
Niobium is used in some alloys of stainless steel, in arc welding rods, in metal alloys used in aircraft construction, in surgical implants, in jewelry, and in some types of glass.
Tantalum (Ta, Z=73)
Tantalum is a hard, gray metal, with a melting point of 3017°C, which is very resistant to corrosion. It is named after a character in Greek mythology, Tantalus (father of Niobe). Tantalus killed his son, Pelops, and served him to the gods at a feast; the gods were not amused, and punished Tantalus in Hades by being made to stand in a pool of water surrounded by trees laden with fruit, but whenever he stooped to drink the water, it receded from him, and whenever he reached out for the fruit, the branches withdrew out of reach, leaving him forever thirsty and hungry. (This is also the derivation of the word "tantalize.") Titanium was difficult to isolate from the chemically-similar niobium (see above), and it was some time before the "tantalizingly" elusive element could be isolated in a pure form. It is found in the Earth's crust at a concentration of 2 ppm, making it the 51st most abundant element. The primary ores of tantalum are tantalite [(Fe,Mn)(Nb,Ta)2O6, called columbite if there is more niobium than tantalum], samarskite [(Y,Ce,U,Fe)3(Nb,Ta,Ti)5O16], and euxenite [(Y,Ca,Ce,U,Th)(Nb,Ta,Ti)2O6].
Tantalum is used in some medical implants, such as pins in bone fractures, and in plating to replace damaged skull bone. It is also used in surgical and dental tools, in electronic capacitors, and in some turbine blades and rocket nozzles.
Tantalum carbide, TaC, is an extremely hard material, and is used in some cutting tools. A composite of tantalum carbide and graphite has been made at Los Alamos National Laboratory, and is one of the hardest materials known, with a melting point of 3738°C.
Dubnium (Db, Z=105).
Dubnium is a synthetic element, produced by the bombardment of californium-249 with nitrogen-15, or berkelium-249 with oxygen-18. The longest-lived isotope, dubnium-262, has a half-life of 34 seconds. The status of the earliest claims for the production of this element was also disputed (see section on Rutherfordium), and for a time was known as both neilsbohrium (Ns), the name proposed by the Russian group at Joint Institute for Nuclear Research, and as hahnium (Ha), proposed by the team at the University of California, Berkeley. In 1997, the IPUAC awarded credit for the discovery of element 105 to both groups, and it was named dubnium, after the city of Dubna, where the JINR is located.
Group 6B (6)
The Group 6B elements (Group 6 in the IUPAC designation) usually have the electron configuration (n-1)d5 ns1, instead of the expected (n-1)d4 ns2. Since their d orbitals are one electron away from being half-filled (i.e., having one electron in each of the five d orbitals), an s electron can move into the d orbitals to make a more stable half-filled d-orbital configuration.
Chromium (Cr, Z=24)
Chromium is a hard, steel-gray metal which can be polished to a high shine. Like many of the other transition metals, it forms a thin oxide coating (chromic oxide, or chromium(III) oxide, Cr2O3) which protects the metal below from further oxidation. The name is derived from the Greek word for color, chroma, because of the wide variety of colorful salts it produces. It is found in the Earth's crust at a concentration of 100 ppm, making it the 21st most abundant element. It is obtained from the ore chromite [FeO·Cr2O3].
Chromium is used in used in spring steels, nickel-chromium steel, stainless steel (up to 15% chromium), iron-nickel-chromium alloys, and metal ceramics. It is also used to electroplate metallic objects to give them a shiny, corrosion-resistant coating; this chrome plating is widely used in automobiles.
In its compounds, chromium is found in the +2, +3, and +6 oxidation states, with the +3 oxidation state being the most stable and the most common. Salts of Cr6+ (also known as hexavalent chromium) are powerful oxidizing agents, and are toxic and carcinogenic. Chromium salts can form a series of colors in solution, ranging from orange (Cr6+ in acidic solution), violet (Cr3+ in basic solution), green (Cr3+ in basic solution), and blue (Cr2+ in acidic solution).
Chromium(III) oxide, or chromic oxide, Cr2O3, is the ninth most abundant compound in the Earth's crust (1800 ppm by weight). Chromite ore can withstand high temperatures, and is used to make some refractory bricks (firebricks), which are used to line furnaces and kilns.
Chromium compounds are also present in a number of dyes and paints, such as lead(II) chromate, PbCrO4, also known as chrome yellow, and chromium(III) oxide, Cr2O3, also known as chrome green or chromic oxide green. Chromium salts are also used in some types of colored glass.
Chromium salts are also responsible for the color of some gemstones. Emeralds are varieties of beryl [Be3Al2(SiO3)6] which contain traces of Cr3+, which gives them a green color. Rubies consist primarily of corundum (aluminum oxide, Al2O3); trace amounts of chromium give the stones a red color. The red light that is produced in ruby lasers is a result of excitation of the chromium atoms. Chromium also gives green and red colors to the gemstone alexandrite, a variety of the mineral chrysoberyl (BeAl2O4).
Small amounts of chromium, the the form of trivalent chromium, Cr3+, are required in the diet. Chromium assists in the metabolism of glucose, but its exact function is not well understood. Chromium deficiency results in mild diabetes and reduced cholesterol levels; this condition is rare in developed countries. There are a wide variety of foods which are plentiful in chromium, such as brewer's yeast, wine, corn oil, whole grains, egg yolks, calf's liver, peanuts, black pepper, and oysters; small amounts are also present in potatoes, beans, carrots, and apples.
Potassium dichromate, K2Cr2O7, is a powerful oxidizing agent (since the chromium is in the +6 oxidation state), and is used in eliminating trace amounts of organic materials from laboratory glassware; it is also used as a mordant for fixing dyes in fabrics. Chromium sulfate, Cr2(SO4)3, is used in the tanning of leather. Chromium(VI) oxide, CrO3, is used in magnetic tapes, such as Type II audiocassette tapes.
Chromium salts also serve as the basis of the "breathalyzer test" for the presence of alcohol. Ethanol (ethyl alcohol), CH3CH2OH, is oxidized by chromium salts, such as potassium dichromate, to produce acetic acid, CH3CO2H. In the process, the chromium is reduced from the +6 oxidation state, which is red-orange in color, to the +3 oxidation state, which is green. If this color change occurs in the test solution, this indicates the presence of alcohol in the breath.
Molybdenum (Mo, Z=42)
Molybdenum is a lustrous, silvery white, relatively soft metal, with a very high melting point (2623°C). It is named for the Greek word molybdos, meaning "lead," because of its similarity to lead. It is found in the Earth's crust at a concentration of 1.5 ppm, making it the 54th most abundant element. It is found in the ores molybdenite [molybdenum sulfide, MoS2], which is very similar to graphite (in fact, both molybdenite and graphite have been used to make pencil "lead"), and wulfenite [lead molybdate, PbMoO4].
Molybdenum is frequently used in alloys with other metals, such as high-temperature steels, and is used to manufacture engine parts, oil pipelines, aircraft parts, and armor plating.
Molybdenum atoms are present in the iron-sulfur protein nitrogenase, which is found in the rhizobia bacteria that are associated with the root nodules of leguminous plants (such as beans, alfalfa, clover, etc.), which convert the nitrogen in the air (in the form of relatively unreactive N2) into ammonia, NH3. Mammals also use molybdenum-containing enzymes to convert nitrogenous wastes into uric acid
Tungsten (W, Z=74)
Tungsten is a hard, steel-gray or white metal, with a melting point of 3422°C — the highest of all of the pure metals. Very pure tungsten can be cut relatively easily, but it becomes much harder and more brittle when it is mixed with impurities. Like many of the other transition metals, it is very resistant to corrosion. The name comes from the Swedish phrase tung sten, meaning "heavy stone." The symbol for the element, W, comes from the German word for the element, wolfram ("wolf dirt," so named because of its presence as an impurity in the mining of tin); the name wolfram is occasionally used for the element instead of tungsten. It is found in the Earth's crust at a concentration of 1 ppm, making it the 58th most abundant element. It is found in the ores wolframite [(Fe,Mn)WO4], scheelite [calcium tungstate, CaWO4], ferberite [iron(II) tungstate, FeWO4], and hubnerite [manganese(II) tungstate, MnWO4].
Tungsten's high melting point and low vapor pressure allows it to be used as the filament in incandescent light bulbs. It is used to make electrodes for Gas Tungsten Arc Welding (GTAW) applications. High-speed steel (HSS) contains iron alloyed with up to 18% tungsten (as well as other metals, such as molybdenum, vanadium and cobalt); these alloys can withstand higher temperatures than carbon steels, and allow machine tools such as drill bits and saw blades to be operated at higher speeds. Tungsten's high density (19.25 g·cm-3) makes it useful for making weights, ballasts, heat sinks, and darts.
In its compounds, tungsten is most often found in the +6 oxidation state, but it is also found with oxidation states of +2, +3, +4, and +5. Tungsten carbide, WC, is one of the hardest substances known, and is used to make cutting tools, dental drills, rock drills for use in mining, and abrasives.
Seaborgium (Sg, Z=106).Seaborgium is a synthetic element, produced by the bombardment of californium-249 with oxygen-18. The longest-lived isotope, seaborgium-266, has a half-life of 27.3 seconds. Scientists at the JINR claimed to have produced element 106 in 1974, but the result could not be confirmed. Albert Ghiorso, at the University of California, Berkeley, produced element 106 in the same year, and confirmed the result in 1993, and was awarded credit for the discovery. Ghiorso suggested the name "seaborgium" for the element, in honor of Glenn T. Seaborg, who had discovered/synthesized a number of transuranium elements. The IUPAC objected to the name, on the grounds that it was inappropriate to name an element after a living scientist.* The American Chemical Society, however, voted to approve the name seaborgium for the element in 1995. After some negotiation, the hotly contested names for elements 104 to 109 were ratified by the IUPAC in 1997, and element 106 was officially designated as seaborgium. Glenn Seaborg died in 1999.
* In fact, there was already precedent for naming elements after living scientists: element 99 was given the name Einsteinium in 1952, and element 100 was given the name Fermium in 1953, while Albert Einstein and Enrico Fermi were still alive. Because of the existence of these elements were "nuclear secrets" during the Cold War (they were discovered in the debris of nuclear tests), the existence of these elements was not publicly known until some time later.
Group 7B (7)
The Group 7B elements (Group 7 in the IUPAC designation) usually have the electron configuration (n-1)d5 ns2.
Manganese (Mn, Z=25)
Manganese is a hard, gray-white metal, which is very brittle, and fairly reactive. It is named for the Latin word for "magnet," magnes, since it can be made to be ferromagnetic with the right treatment. It is found in the Earth's crust at a concentration of 1000 ppm, making it the 12th most abundant element. Its ores include pyrolucite [manganese(IV) oxide, MnO2], rhodochrosite [manganese(II) carbonate, MnCO3], and manganite [MnO(OH)]. In addition, manganese-rich nodules are scattered across much of the ocean floor, but there is no practical way of obtaining them.
Manganese is used in alloys with steel to improve strength and resistance to wear. Manganese steels are extremely strong, and are used in railroad tracks, earth-moving machinery, and other applications.
In compounds, the most common oxidation states of manganese are +2, +3, +4, +6, and +7. Manganese(II) oxide, MnO, is the tenth most abundant compound in the Earth's crust (1400 ppm). Potassium permanganate, KMnO4, is a deeply purple crystalline substance when pure, and forms purple solutions when dissolved in water; it is a strong oxidizing agent, and is used in bleaches, disinfectants, deodorizers, and as a reagent for some reactions in organic chemistry. Traces of manganese give amethysts, which are composed primarily of silicon dioxide, their characteristic purple color.
Manganese is also an essential trace nutrient, and is involved in the action of vitamin B1 (thiamine) in the metabolism of carbohydrates. Nuts and cereals have fairly high levels of manganese.
Technetium (Tc, Z=43)
Technetium is a radioactive element; the pure metal is silvery-gray in appearance, although it usually used as a grey powder. It is named for the Greek word technetos, meaning "artificial," because it was the first element to be produced artificially. Trace amounts of technetium are found in uranium ores, where it is produced by spontaneous fission of uranium-238, but the element is not present in large enough quantities to be practically mined (the concentration is estimated at about 1 nanogram per kilogram of ore). It is also obtained from spent uranium-235 fuel rods in nuclear reactors.
Technetium is produced by the neutron bombardment of molybdenum-98 to produce molybdenum-99, which then undergoes beta-decay with a half-life of 67 hours to produce technetium-99m, a metastable, excited nuclear state with a half-life of 6 hours, which emits gamma rays to form ground-state technetium-99. Technetium-99 is also radioactive, and is a beta-particle emitter with a half-life of 211,000 years.
There are about 56 isotopes of technetium (including metastable states), and all of them are radioactive. The longest-lived isotope, technetium-98, has a half-life of 4.2 million years. That may seem like a long time, but compared to the age of the Earth — 4.5 billion years — that is enough time for any technetium that had originally been in the Earth's crust to have decayed. In 1952, traces of technetium were discovered in the spectra of some types of red giant stars; this was one of the first pieces of evidence to support the theory that heavy elements were produced in stars.
The existence of technetium was predicted from the gap in the periodic table between the elements molybdenum (Z=42) and ruthenium (Z=44), but element 43 proved to be extremely elusive. Many early reports of its discovery turned out to be mistaken, being instead impure samples of other, known elements. The element was finally discovered in 1937 by Emilio Segre and Carlo Perrier at the University of Palermo in Italy, in a sample of molybdenum-96 that had been bombarded with deuterium (hydrogen-2), producing technetium-97. The element may have been discovered earlier by Walter Noddack, Otto Berg, and Ida Tacke in 1925, who bombarded a sample of columbite [(Fe, Mn)(Nb, Ta)2O6] with a beam of electrons, and reported an X-ray signal that they believed to be element 43, which they named "masurium" after after Masuria in eastern Prussia (now a part of Poland). However, their results could not be reproduced, and their claim was not accepted; recent research indicates they they may indeed have been able to produce very small amounts of element 43 by this method after all.
Technetium is used in several applications in nuclear medicine as a radioactive tracer, since it emits gamma rays that are detectable by imaging devices. It is obtained from a technetium-99m generator, also known as a "technetium cow," in which radioactive molybdenum-99 (with a half-life of 67 hours) is adsorbed onto an alumina chromatography column; the molybdenum-99 decays to water-soluble technetium-99m, which is extracted from the column by passing a saline solution through it (the process is naturally referred to as "milking"), whereupon it can be mixed with the reagent that is appropriate for the particular imaging technology to be used. In immunoscintigraphy, radioactive technetium-99m is incorporated into a monoclonal antibody which binds to cancer cells; this technique is used to detect intestinal cancers, which are difficult to locate by other techniques. In combination with tin compounds, technetium-99m binds to red blood cells, and can be used to map the circulatory system; this is particularly useful in diagnosing some types of congestive heart failure and in determining the damage done to the heart muscle by a heart attack.
Ammonium pertechnate, NH4TcO4, and other technetium salts, can be used as corrosion inhibitors for steel, however, because of the radioactivity of technetium, this is useful only in closed systems.
Rhenium (Re, Z=75)
Rhenium, id a silvery-white, hard metal. It is resistant to corrosion, but slowly tarnishes in moist air. It has the third-highest melting point of all of the elements, at 3186°C; it is also one of the highest densities, at 21.02 g/cm3. It is named for named for the Latin word for the Rhine River, Rhenus. It is found in the Earth's crust at a concentration of 0.5 ppb, making it the 77th most abundant element. It occurs as an impurity in molybdenite, copper sulfide, and other ores.
Rhenium is used in alloys with tungsten and molybdenum to make filaments for ovens and lamps, and is also used in electroplating jewelry. It is also used in combination with platinum to make catalysts for generating high-octane gasoline from crude oil.
Rhenium was discovered by Walter Noddack, Otto Berg, and Ida Tacke in 1925, as a trace element in columbite, gadolinite, molybdenite and platinum ores. It was the last of the naturally occurring elements to be discovered, in part because of its extremely low concentration in the Earth's crust and because it is not concentrated in any unique minerals or ores.
Bohrium (Bh, Z=107).
Bohrium is a synthetic element, produced by the cold fusion of bismuth-209 and chromium-54. The longest-lived isotope, bohrium-262, has a half-life of 0.1 seconds. As is the case with several of the transfermium elements on the periodic table, there was some controversy over the initial discovery of element 107, in this case between the Laboratory for Heavy Ion Research (GSI, Gesellschaft für Schwerionenforschung) in Darmstadt, Germany, and the JINR in Dubna. The IUPAC concluded that the GSI group should be awarded credit for the discovery, but both groups were allowed to collaborate on choosing a name for the element. They chose "neilsbohrium" in honor of the Danish physicist Niels Bohr; this was shortened to "bohrium" in 1997.
Group 8B (8, 9, 10)
The Group 8B elements are designated Groups 8, 9, and 10 in the IUPAC designation. The elements in each period of these groups are very similar in their chemical and physical properties. The Group 8 elements usually have the electron configuration (n-1)d6 ns2, the Group 9 elements usually have the electron configuration (n-1)d7 ns2, and the Group 10 elements usually have the electron configuration (n-1)d8 ns2.
Iron (Fe, Z=26)
Iron in its pure form is a malleable, ductile, silvery metal. The name comes from the Anglo-Saxon word for the metal, iren; the chemical symbol "Fe" is derived from the Latin word for iron, ferrum. It is the fourth most abundant element in the Earth's crust, having a concentration of about 4.1% by mass. Its most common ores are hematite [iron(III) oxide, Fe2O3], magnetite [Fe3O4, actually a mixture of Fe2O3 and iron(II) oxide, FeO], goethite and lepidocrocite [iron(III) oxide hydroxide, FeO(OH)], and siderite [iron(II) carbonate, FeCO3].
Iron compounds are extremely common: iron(II) oxide, or ferrous oxide, FeO, is the third most abundant compound in the Earth's crust, having a concentration of 89,700 ppm, and iron(III) oxide, or ferric oxide, Fe2O3, is the seventh most abundant compound, with a concentration of 3600 ppm. The Earth's core, with a diameter of about 7000 kilometers, is about 80% iron, along with nickel and other metals, although this is somewhat more inaccessible than the iron ore in the crust (except in really bad science fiction movies). According to the dynamo theory, convection current in the molten iron and nickel of the outer core give rise to Earth's magnetic field. Iron-56 is the final product of nuclear fusion in average-sized stars like the Sun; the fusion of iron requires an input of energy, and in these stars, iron accumulates in their centers as their nuclear fuel becomes spent.
Iron has been used by humans at least as far back as 3500 BC, mostly for ceremonial purposes because of the difficulty in obtaining it in its pure form. The iron that was used in this way was often recovered from meteorites. The processing of smelting iron from its ores was discovered in Asia Minor around 1500 BC. Iron ore from Magnesia in Lydia, Asia Minor, was discovered to attract other pieces of iron; this ore was named "magnetite" and the attractive pieces of metal were named "magnets" after their country of origin.
Iron is extracted from its ores by smelting the ores in a blast furnace with coke, a low-ash carbonaceous residue obtained from bituminous coal, and limestone (calcium carbonate, CaCO3), which is used as a flux to melt impurities in the ore. The product of this process is "pig iron," containing 3-5% carbon and other impurities. This is further refined to produce either pure iron or an alloy. Pure iron is a fairly soft metal, and corrodes easily, and is often alloyed with other metals to improve its strength and durability. Steel is iron containing from between 0.3% to 1.7% carbon; the resulting metal is much less brittle and more corrosion-resistant than pure iron; steel is the most common metal used for construction purposes. Cast iron contains from 3 to 5% carbon, and while not as hard as steel, it is much cheaper. These steels can be alloyed with other metals, such as nickel, tungsten, vanadium, and manganese, to make extremely durable materials. Stainless steel contains up to 18% chromium and 8% nickel, and is very useful in kitchen utensils.
Many of the transition metals oxidize to produce metal oxides that adhere tightly to the exposed metal, protecting the metal surface against further oxidation. When iron oxidizes, however, the iron(III) oxide, Fe2O3, that is generated flakes off of the metal surface, exposing more of the metal to further oxidation. The reaction for the rusting of iron is commonly written as 4Fe + 3O2 ® 2Fe2O3, but the actual chemistry is much more complicated, since water must also be present for the reaction to occur. Iron metal is converted to Fe2+ at some places on the exposed metal, as a result of exposure to oxygen from the air dissolved in droplets of water on the surface. The Fe2+ dissolves into the water droplet, and is further oxidized by oxygen to Fe3+. The oxygen is reduced to water by the electrons released by the oxidation of iron, since the electrons are easily carried through the conductive metal. The water droplets act as the electrolyte solution that completes the electrical circuit between the region where the iron is oxidized and dissolved out of the metal surface, and the region in which it is precipitated out as insoluble reddish-brown flakes of Fe2O3·H2O, better known as rust. Rust can be removed from iron by "pickling" it with an acid: rinsing the metal surface with an acid, such as hydrochloric acid, dissolves the Fe3+ ions, allowing them to be washed away.
Iron's longevity can be extended by coating it with zinc to produce galvanized iron. Zinc is more easily oxidized than iron, and so under conditions in which a metal can be oxidized, the zinc is oxidized instead of iron. Galvanized iron is used in car parts, outdoor fences, and other applications. The same idea is exploited in tinplate, in which a sheet of iron is coated with a thin layer of tin. This is used in the manufacture of tin cans. This type of protection is referred to as cathodic protection, since the iron acts as a cathode, where reduction takes place — that is, any Fe2+ or Fe3+ that is in the process of being generated is immediately reduced by electrons from the oxidization of zinc or tin (which act as the anodes). In many cases, it is unnecessary to coat the entire iron surface with another metal; instead, the iron is placed in electrical contact with a "sacrificial anode" made of an easily oxidized metal such as magnesium, zinc, or aluminum. This process is used to protect underground steel pipelines, boat hulls and propellers, and water heaters. These metal anodes are usually designed to be easily replaceable, so that when they are used up (i.e., "sacrificed"), they can be replaced with a fresh sample of metal, to continue to protect the iron.
The most common oxidation states of iron are Fe2+, the ferrous or iron(II) ion, and Fe3+, the ferric or iron(III) ion. Iron can also exist in the -2, -1, 0, +1, +4, and +6 states as well. Iron(III) oxides are used to make magnetic storage media. Iron pyrite, FeS2, [iron disulfide, or iron(II) sulfide (actually Fe2+ combined with a disulfide anion, S22-)] is also known as "fool's gold" because its yellow color makes it look a lot like gold.
A "ferrous" wheel
Iron is an essential nutrient for almost all living organisms. Of the 4 grams of iron in the average human adult, about 65% is incorporated into the protein hemoglobin, which carries oxygen in the bloodstream from the lungs to the cells. The hemoglobin protein consists of four subunits, each of which contains a molecule called heme, a porphyrin ring which binds an iron in the +2 oxidation state; oxygen molecules "stick" to the iron ion, allowing transport of oxygen from the lungs to the various tissues of the body. Iron is also involved in the function of many of the body's enzymes, including those which synthesize DNA and those which metabolize carbohydrates. Iron is also bound by the transferrin protein, which carries iron between various cells in the body; it also acts as an antibiotic by preventing the uptake of iron by invading bacteria. Iron is easily obtained in the diet, from foods such as red meat, fish, poultry, liver, breakfast cereals, wine, lentils, beans, black-eyed peas, leafy vegetables, tofu, peanut butter, raisins, bread, and eggs. Despite the nutritional recommendations from the "Popeye" cartoons, spinach is not actually a good source of iron — even though it contains 2.7 mg per 100 g of spinach leaves, the oxalate ions (C2O42-) that are also found in spinach bind the iron very tightly, decreasing the amount that the body can extract.
Cobalt (Co, Z=27)
Cobalt is a hard, lustrous bluish-gray metal. It is named for the German word for "goblin," kobold, because of the toxic fumes of arsenic that were produced when silver miners heated the ore smaltite, CoAs2, mistaking it for silver ore. It is found in the Earth's crust at a concentration of 20 ppm, making it the 32nd most abundant element. Cobalt is found in the ores cobaltite [(Co, Fe)AsS] and erythrite [cobalt(III) arsenate, Co3(AsO4)2], although it is more commonly obtained as a by-product of nickel and copper mining.
Cobalt has been used to produce deeply blue colors in glass and pottery since the time of the Ancient Egyptians. Today, cobalt is used in many types of alloys, ceramics, stained glass (known as cobalt glass), magnets, and magnetic recording media. Cobalt is not as magnetic as iron, but its magnetic properties are retained at higher temperatures than iron; it is alloyed with aluminum and nickel to make strong, permanent Alnico magnets.
Radioactive cobalt-60 is made by bombarding cobalt-59 with neutrons in a nuclear reactor. Cobalt-60 has a half-life of 5.3 years, undergoing beta-decay to produce nickel-60, and emitting gamma rays in the process. Cobalt-60 used used as a radiation source in some medical equipment, and is also used in irradiating food and detecting structural defects in metals.
In its compounds, cobalt typically forms +2 and +3 ions. Salts of Co2+ tend to form reddish-pink colors in aqueous solution, because of the formation of the complex ion [Co(OH2)6]2+. Replacing the hydroxide anions with chloride anions forms the blue complex [CoCl4]2-.
Cobalt is essential in the diet because it is incorporated into Vitamin B12(cyanocobalamin), which is necessary for the prevention of pernicious anemia.
Nickel (Ni, Z=28)
Nickel is a hard, malleable, silvery metal. The name is derived from the German word kupfernickel, meaning "Old Nick's copper" (i.e., copper of the devil, or false copper) because it was frequently mistaken for copper. It is found in the Earth's crust at a concentration of 80 ppm, making it the 23rd most abundant element. It is found in the ores millerite [nickel sulfide, NiS], pentlandite [(Fe,Ni)9S8], nickeline [nickel arsenide, NiAs], nickeliferous limonite [(Fe,Ni)O(OH)], and garnierite [(Ni,Mg)3Si2O5(OH)]. About 10% of the Earth's core is also composed of nickel.
Because of its high resistance to oxidation, it is frequently used in coins. The "nickel," the US five-cent piece, is composed of 25% nickel and 75% copper.
Nickel is more commonly used in alloys rather than as the pure metal. Pure nickel is ferromagnetic, and is used in some permanent magnets, such as Alnico magnets which are composed of an alloy of aluminum, nickel, and cobalt. Stainless steel is an alloy of iron and chromium which contains about 8% nickel. Invar ("invariable") is an alloy of 64% iron and 36% nickel which does not expand when heated. Nichrome is an alloy of nickel and chromium (11 to 22%) which is stable at high temperatures, and is used in the heating elements of ovens and toasters. Monel is an alloy of 70% nickel and 30% copper which does not corrode in sea water, and is used for propeller shafts in boats. Platinite is an alloy of 46% nickel and 54% iron, and is used in light bulbs. Nickel aluminide, Ni3Al, is an unusual alloy which is six times stronger than stainless steel, and becomes stronger at higher temperatures, making it of potential use in rocket engines. Nitinol, (an acronym of Nickel Titanium, Naval Ordnance Laboratories, where this alloy was developed) is an alloy of 55% nickel and 45% titanium, which is a "shape memory alloy" that has the ability to be deformed, and return to its previous shape; this makes ideal for use in frames for glasses, and dental braces.
Nickel powder or Raney nickel (a nickel-aluminum alloy) are used as catalysts for the production of hydrogenated oils, in which unsaturated fats, which contain carbon-carbon double bonds, and tend to be liquids at room temperature, are reacted with hydrogen gas to produce saturated fats, which contain carbon-carbon single bonds only, and tend to be solids at room temperature. The hydrogen and unsaturated fats are adsorbed onto the surface of the metal, which slightly weakens the hydrogen-hydrogen bonds and the carbon-carbon double bond; when the hydrogen "bumps" against the weakened bond, the hydrogen atoms are added to the carbon-carbon double bond, producing a single bond, and the saturated product drifts away from the metal surface, leaving it free to react with more of the reactants. This process is used in the production of shortening from vegetable oils, and the production of margarines and other spreads.
In its compounds, nickel is most commonly found in the +2 oxidation state [the nickel(II) ion, or "nickelous" ion], although +1, +3 and +4 states also exist.
Nickel-cadmium batteries (NiCad, or NiCd) use nickel oxide-hydroxide, NiO(OH), at the cathode (the positive electrode), and cadmium metal at the anode. As the battery discharges, the nickel is reduced from the +3 oxidation state to the +2 oxidation state, and the cadmium is oxidized to the +2 oxidation state. The battery can be recharged, using an external source of electricity to run the reactions in reverse, allowing the battery to be reused.
Ruthenium (Ru, Z=44)
Ruthenium is a silver-gray, extremely brittle, and stable metal. It named from the Latin word for Russia, Ruthenia. It is found in the Earth's crust at a concentration of 1 ppb, making it the 74th most abundant element. It is found in the ores laurite [ruthenium sulfide, RuS2], ruarsite [ruthenium arsenic sulfide, RuAsS], and ruthenarsenite [(Ru,Ni)As], although it is usually obtained as a by-product from the refining of nickel and platinum.
Ruthenium is used in the electronics industry in some electrical contacts and chip resistors. It is also used in the anodes used to produce chlorine in electrolytic cells. It is also used in alloys with platinum and palladium in jewelry to harden the metals.
Rhodium (Rh, Z=45)
Rhodium is a silvery, hard, unreactive metal. It is named from the Greek word for rose, rhodon, because of its red-colored salts. It is found in the Earth's crust at a concentration of 0.2 ppb, making it the 78th most abundant element. It is found in some areas as the free metal, and in the ore rhodplumsite [(Rh3Pb2S2)], and is also found in some platinum ores.
Rhodium is used as a part of the catalyst in automobile catalytic converters that reduce the emissions of nitrogen oxides, carbon monoxides, and unburned hydrocarbons. It is also used to make reflective surfaces for optical fibers and headlights, as a hardener for platinum and palladium, and is electroplated on white gold to produce a jewelry called rhodium flashing. Because of its unreactivity and high melting point (1964°C), it is also used in some high-temperature crucibles.
Palladium (Pd, Z=46)
Palladium is a soft, malleable and ductile, silvery-white metal. It is found in the Earth's crust at a concentration of 0.6 ppb, making it the 76th most abundant element. It is named after the asteroid, Pallas, which had been discovered in the same year that the metal was first isolated (1802). Palladium is occasionally found as the free metal, and also in the ores stibiopalladinite [palladium antimonide, Pd5Sb2] and braggite [(Pd,Pt,Ni)S], but is most commonly obtained as a by-product of the mining of copper, silver, and gold.
Palladium is used in catalytic converters, dental fillings, jewelry (as an alloy with gold called white gold), in the mainsprings of analog wristwatches, and the ceramic capacitors used in many electronic devices. Palladium(II) chloride, PdCl2, is used in instruments for detecting carbon monoxide.
Palladium can absorb up to 900 times its own volume of hydrogen gas, possibly forming palladium hydride, PdH2, in the process.
Osmium (Os, Z=76)
Osmium is a hard, lustrous, blue-gray or blue-black metal. Its name is derived from the Greek word for odor, osme, because of its nasty smell (which is actually caused by osmium tetroxide). It is found in the Earth's crust at a concentration of 0.1 ppb, making it the 79th most abundant element. It is found as the free metal, and in iridosmine and osmiridium, alloys of osmium and iridium that may also contain traces of platinum and rhodium. Osmium is also found in some platinum ores, and is commercially obtained as a by-product from nickel refining.
Osmium is the densest metal known, at 22.588 g/cm3, although iridium is a very close contender at 22.562 g/cm3. Osmium is not very reactive, but the powdered form does react with oxygen in the air to produce osmium tetroxide, OsO4, which is poisonous, and has a unpleasant odor similar to that of ozone.
Osmium is used as in some alloys agent to minimize wear due to friction, and is also used in in electrical switch contacts, in some ballpoint pen and fountain pen tips, and in phonograph needles (a rapidly diminishing usage!).
In organic synthesis, osmium tetroxide is used to produce vicinal diols (which have two OH groups on neighboring carbons) from alkenes (molecules containing carbon-carbon double bonds). Since osmium reagents are very expensive, the reaction is usually performed with an oxidizing agent in the same reaction vessel, which oxidizes the osmium reagent back into osmium tetroxide, allowing it to be used in catalytic amounts rather than in stoichiometric amounts.
Iridium (Ir, Z=77)
Iridium is a hard, brittle, silvery-white metal. It is named from the Latin word for "rainbow," iris, because of the colorful compounds that it forms. It is found in the Earth's crust at a concentration of 3 ppt, making it the 82nd most abundant element. It is found as the free metal, and in iridosmine and osmiridium, alloys of iridium and osmium that may also contain traces of platinum and rhodium. Most iridium is obtained as a by-product from the refining of platinum.
Iridium is the second densest metal known, at 22.562 g/cm3, not far behind osmium at 22.588 g/cm3. It is the most corrosion-resistant of all known metals, able to withstand even got aqua regia. It is extremely rare, having a concentration in the Earth's crust of 3 ppt.
Iridium is used as an alloying agent for hardening platinum, in fountain pen tips and compass bearings, in the tips of automobile spark plugs, in the electrodes used in the chlor-alkali process.
Iridium also provided the smoking gun for the event that caused the extinction of the dinosaurs 65 million years ago. Geologists discovered that the boundary between the Cretaceous and Tertiary periods (the K-T boundary) was enriched in iridium. The noted geologist Walter Alvarez hypothesized that since asteroids are rich in iridium, a large asteroid may have collided with the Earth 65 million years ago, causing severe climate changes that led to the extinction of the dinosaurs and many other forms of life. The evidence seems to indicate that a bolide measuring about 5 to 15 kilometers across hit the Earth in what is now the Yucatán Peninsula, creating the the Chicxulub Crater.
Platinum (Pt, Z=78)
Platinum is a very heavy, soft, malleable and ductile, silvery-white metal. It is named from the Spanish word platina, meaning "little silver," because it was first known (to Europeans, anyway) as an unworkable silver-like metal found alongside gold in some deposits. It is found in the Earth's crust at a concentration of 1 ppb, making it the 75th most abundant element. It occurs naturally as the free metal, in an alloy with iridium called platiniridium, and in the ores cooperite [(Pt,Pd,Ni)S] and sperrylite [platinum arsenide, PtAs2]
The platinum metals are ruthenium, rhodium, palladium, osmium, iridium, and platinum. These metals share many important physical and chemical properties, and are often found in close proximity to each other in natural sources, often in the uncombined metallic form.
Platinum is extremely stable and corrosion-resistant. It has the third highest density of all known metals, at 21.45 g/cm3, and a very high melting point, at 1768°C. It is a very rare element, having an abundance of about 1 ppb in the Earth's crust. Platinum was mined and worked by Native Americans in South America as far back as 2000 years ago. Platinum is considered one of the precious metals because of its rarity, stability, high melting point, and high luster.
Platinum is used in jewelry, catalytic converters, laboratory instruments, medical and dental instruments, electrical contacts, electrodes for electrolysis, computer hardware (about 80% of all hard disk drives contain platinum), fiber optical cable and LCD displays, and fuel cells. The standards for the meter and the kilogram housed at the International Bureau of Weights and Measures in Paris, France, are made of platinum alloyed with 10%iridium.
In organic synthesis, platinum is used to catalyze the reactions of alkenes (which contain carbon-carbon double bonds) to alkanes (which contain only carbon-carbon single bonds). The finely divided metal can adsorb molecules of the alkene and hydrogen gas onto its surface, weakening the C=C bond and the H-H bond, and releasing the product alkanes when they have reacted with each other.
In its compounds, the most common oxidation states of platinum are +2 and +4, but +3 and +6 states are also known.
Cisplatin, PtCl2(NH3)2, also known as Platinol, Peyrone's chloride, and more formally as cis-diamminedichloroplatinum(II), is used in the chemotherapeutic treatment of some cancers. It works by attaching itself to sections of DNA which contain two guanine units next to each other; since it affects healthy cells as well as cancer cells, it causes a number of side effects, but many of these effects can be treated with other medications.
Hassium (Hs, Z=108)
Hassium is a synthetic element, produced by the cold fusion of lead-208 and iron-58. The longest-lived isotope, hassium-270, was recently reported (story) to have a half-life of 30 seconds, which is considerably more stable than many of the transuranic elements.. It was first produced at the GSI in Darmstadt, Germany, in 1984, and was named after the German state of Hesse, where the GSI is located.
Meitnerium (Mt, Z=109)
Meitnerium is a synthetic element, produced by the cold fusion of bismuth-209 and iron-58. The longest-lived isotope, meitnerium-268, has a half-life of 0.07 seconds. It was first produced at the GSI in Darmstadt, Germany, in 1982, and was named after Lise Meitner, the Austrian physicist who was a member of the research team that first observed nuclear fission in uranium, and was the first to recognize that the results of their experiment indicated that fission had taken place.
Darmstadtium (Ds, Z=110).
Darmstadtium is a synthetic element, produced by the bombardment of lead-208 with nickel-62. The longest-lived isotope, darmstadtium-279, has a half-life of 180 milliseconds. It was first produced at the GSI in Darmstadt, Germany, in 1994, and was named for the city in which is was first produced.
Group 1B (11)
The Group 1B elements (Group 11 in the IUPAC designation) have the electron configuration (n-1)d10 ns1, instead of the expected (n-1)d9 ns2; since in d9 s2 configuration the d orbitals are one electron away from being completely filled, an electron from the s orbital occupies a d orbital instead, leaving one electron in the valence shell. These metals usually form 1+ charges, which is why this group has historically been called 1B. The elements in this group are sometimes referred to as "coinage metals" because they have historically been used in coins, although other metals besides the ones in Group 1B have been used in coins as well.
Copper (Cu, Z=29)
Copper is a malleable, ductile, reddish-brown metal. Its name is derived from the Old English name coper, which is in turn derived from the Latin word cuprum for "from the island of Cyprus," which was the leading supplier of copper in the Mediterranean area at the time of the Roman empire. The symbol "Cu" is derived from cuprum. Copper is not an extremely common element in the Earth's crust, having a concentration of only 50 ppm in the Earth's crust (making it the 26th most abundant element), but it is relatively easy to obtain because it is highly concentrated in its ores. Some copper is found as the pure metal form in 99% or better purity; the ores of copper include chalcopyrite [CuFeS2], chalcocite [copper(I) sulfide, Cu2S], covellite [copper(II) sulfide, CuS], bornite [Cu5FeS4], cuprite [copper(I) oxide, Cu2O], tenorite [copper(II) oxide, CuO], paramelaconite [a mixture of copper(I) and copper(II) oxides], chalcanthite [copper(II) sulfate pentahydrate, CuSO4·5H2O], and and brochantite [a mixture of copper(II) sulfate and copper(II) hydroxide, CuSO4·3Cu(OH)2], malachite [copper(II) carbonate hydroxide, Cu2CO3(OH)2],and azurite [a mixture of two parts copper(II) carbonate and one part copper(II) hydroxide, Cu3(CO3)2(OH)2].
Copper artifacts have been found which date back to about 10,000 years ago; the refining of copper ores started at around 5000 BC. However, copper is a soft metal, and is not unsuitable for making tools and weapons. The Bronze Age began in around 3000 BC when it was discovered that copper could be alloyed with tin (at a ratio of about two parts copper to one part tin) to make bronze; the resulting alloy was much stronger, and was capable of holding an edge.
Copper is a good conductor of heat and electricity, and is used extensively in electrical wiring. For this usage, it must be extremely pure, because trace amounts of other metal decrease the electrical conductivity and increase the amount of resistance in copper wiring. Copper can be roasted and smelted from its ore in about 99% purity, but this is still not good enough for use as wiring. Copper is further refined in an electrochemical process, in which impure copper is used at the anode of the electrolytic cell, and a sheet of very pure copper is used as the cathode. Copper is oxidized at the anode into Cu2+ ions, which dissolved in the electrolyte solution, and are are reduced at the cathode, plating out on the electrode as copper metal in better than 99.6% purity. Other easily oxidized metal ions, such as Zn2+ and Fe2+ remain in the electrolyte solution, and less easily oxidized metals fall to the bottom of the cell as "anode mud," which contains such “impurities” as silver, gold, and platinum.
Copper was widely used to make cookware such as pans and kettles, but this use is less common now because of widely available cheaper cookware made of aluminum or stainless steel. Many high-quality pots and pans are made with copper bottoms, which distributes the heat from the stovetop quickly and evenly throughout the pan.
Because copper resists corrosion by water, air, and most acids (except for concentrated nitric and sulfuric acids), it is ideal for making coins. The US one-cent piece, the penny, used to be made from solid copper (or copper alloyed with tin, nickel, or zinc) but due to the increasing cost of copper, this was replaced in 1982 with a coin made from a zinc core surrounded by a thin copper plating (about 2.4% of the mass of the coin). [An interesting chemical demonstration can be done with these kinds of pennies: if the copper on the edge of the penny is filed off to expose the zinc, and the coin dropped into hydrochloric acid, the zinc will undergo a single-displacement reaction with the hydrochloric acid and dissolve in the solution as soluble zinc chloride, ZnCl2, while the copper on the obverse and reverse sides of the penny will remain unaffected, leaving two thin pieces of copper foil still bearing the impressions of the Lincoln head and the Lincoln Memorial.] The US five-cent piece, the nickel, is an alloy of 75% copper and 25% nickel; and the the ten-cent piece (the dime) and 25-cent piece (the quarter) are 91.67% copper and 8.33% nickel. The US Sacajawea dollar coin, first issued in November of 1999 is also made primarily of copper (88.5% copper, 6% zinc, 3.5% manganese, and 2% nickel).
Copper is also widely used in plumbing and water pipelines, motors and generators, circuitry and computer chips, household fixtures, kitchen utensils, dinnerware (such as sterling silver, which consists of silver alloyed with 7.5% copper or some other metal), in ceramic glazes and colored glass, and in musical instruments (especially those made of brass).
Copper is also widely used in statuary. The Statue of Liberty is made of 81.3 tons of copper plating mounted on a steel skeleton. The Colossus of Rhodes, one of the Seven Wonders of the Ancient World, was a 110-foot bronze statue of the Greek god Helios on the island of Rhodes which stood at the mouth of the Mandraki harbor entrance; it was completed in 280 BC and destroyed by an earthquake in 224 BC.
Copper is used to make several important metal alloys. Bronze is an alloy of copper and tin. Brass is an alloy of copper and zinc, which is addition to being harder than copper can be polished to a high, golden luster. Gunmetal (also known as red brass) is an alloy of copper, tin, and zinc which is strong enough to make guns and cannons. Cupronickel (also called Monel metal) is an alloy of copper and nickel commonly used in coins, such as the US 5-cent piece, and in shipbuilding. Alloys of copper and nickel are also used in desalination plants and underwater pumps because it resists corrosion by sea water. Aluminum bronzes are alloys of copper and up to 7% aluminum that have a gold luster, and are very resistant to corrosion; they are used in naval architecture, engine parts on ships, and landing gear components.
The most common oxidation states of iron are Cu+, the copper(I) or cuprous ion, and Cu2+, the copper(II) or cupric ion. Copper(II) sulfate, CuSO4, is white in is anhyrous form, and deep blue when it is complexed with water in the pentahydrate form, CuSO4·5H2O. This material, sometimes called blue vitrol, is used in fungicides and algicides, and in ink pigments. Copper(II) chloride, CuCl2, is used as a dye fixer in the textile industry. Copper(II) acetate, Cu(C2H3O2)2, also known as verdigris, forms as copper is exposed to air and seawater over long periods of time; it is widely used as a green pigment in oil paintings.
Copper is essential in the diet because it is a part of several enzymes in the body, such as cyctochrome c oxidase, which is required for energy production. Copper is plentiful in foods such as seafood (especially shellfish), lamb, duck, pork, and beef, almonds, walnuts, Brazil nuts, sunflower seeds, mushrooms, and bran. The minimum amount of copper needed in the diet is around 1.2 mg per day, but a typical diet can provide as much as 6 mg per day.
Some mollusks (such as oysters) and some arthropods (such as the horseshoe crab) use hemocyanin to carry oxygen to their cells. In this protein complex, a copper(I) ion is held in place by histidine groups; molecular oxygen complexes with the copper ion to form a blue copper(II)-oxygen complex. (In Star Trek, Vulcan blood was green because it was copper-based.)
Silver (Ag, Z=47)
Silver is a soft, ductile, malleable, silvery (duh) metal. The name is derived from the Anglo-Saxon word for the metal, siolfur; its chemical symbol, Ag, is derived from the Latin name for silver, argentum. Silver is a fairly rare element, having a concentration of 70 ppb in the Earth's crust, making it the 66th most abundant element. It is found in the ores argentite and acanthite [both silver sulfide, Ag2S], stephanite [silver antimony sulfide, Ag5SbS4], horn silver [silver chloride, AgCl], silver arsenide [Ag3As], bromyrite [AgBr], and cerargyrite [AgCl]. However, most silver is obtained as a by-product from the refining of other metals.
Silver was known in many ancient civilizations, but since is not obtained from the ground as the pure metal, it has not been used for as long as gold has been. Silver was first mined around 3000 BC, and was extensively used in coins, although silver coins are too soft to be very durable.
Silver is the metal which is most conductive to electricity and heat, which makes is extremely important in the electronics industry. The metal is extremely malleable and ductile — one gram of silver can be drawn into a wire nearly two kilometers long. Silver is is stable to water and oxygen, but forms silver sulfide, Ag2S, when it is exposed to sulfur compounds in the air; this forms a black coating (tarnish) on the silver, which requires regular cleaning. Silver is considered one of the precious metals because of its rarity, stability, high melting point, and high luster.
Silver is widely used in the electronics industry in switches, circuits, and electronic devices (such as computer keyboards). It is also used in cutlery, jewelry, and mirrors. Sterling silver is an alloy of 93% silver and 7% copper which is widely used in tableware. Amalgams of silver, tin, and mercury are used by dentists to fill cavities.
In its compounds, silver typically is in the +1 oxidation state, but some +2 and +3 compounds are also known. Silver nitrate, AgNO3, is used in photographic emulsions, as are silver bromide, AgBr, silver chloride, AgCl, and silver iodide, AgI. Silver iodide is used in used to seed clouds to encourage rainfall.
Colloidal silver is a suspension of silver used in "alternative" medicine as a antibiotic. However, prolonged use, or overdoses, of colloidal silver can lead to a condition called argyria, in which silver becomes deposited in tissues throughout the body, causing the skin to become bluish-gray. Although this is not harmful in itself, it is disfiguring, and it may not be possible to reverse the condition.
Gold (Au, Z=79)
Gold is a soft, malleable, yellow metal. It is an extremely rare element, having a concentration of 1 ppb in the Earth's crust, making it the 73rd most abundant element. The name is derived from the Anglo-Saxon language, while the chemical symbol "Au" is derived from the Latin name for the metal, aurum ("shining dawn"). It is often found as the free element as nuggets or grains, and in alluvial deposits, and is associated with some sulfide ores, and is also found in the mineral sylvanite [silver gold telluride, (Ag,Au)Te2].
Gold has been used by humans for thousands of years. Since uncombined gold can be obtained directly from the ground (or by panning streams and rivers), and is easy to refine because it has a relatively low melting point (1064ºC) it was one of the first metals to be discovered, and was widely used in making jewelry, coins, and other artifacts. The desire for gold encouraged the ancient alchemists to try to figure out how to make the "Philosopher's Stone" that would enable them to transmute base metals such as lead into gold. Although they never succeeded (except perhaps for Nicholas Flamel, in the Harry Potter books by J. K. Rowling), they did accumulate a lot of empirical observations that led to the development of the science of chemistry.
Gold is extremely unreactive: the only acids that dissolve gold are aqua regia ("king of waters," a mixture of concentrated hydrochloric acid and nitric acid), and selenic acid, H2SeO4. Gold extremely malleable and ductile: one gram of gold can be beaten out to make a thin film that is one square meter in area and 50 nanometers in thickness. Gold is also a very good electrical conductor, making it useful in electrical connections. The oceans contain roughly 10 million tons of gold, but it is at such a low concentration — about 10 parts per thousand — that is impractical to try to extract it. Like silver, gold is considered one of the precious metals because of its rarity and stability.
Gold is used extensively in jewelry (this accounts for about 75% of all gold produced), in bullion (precious metals in bulk form), and in electronics. Thin films of gold are used in some large buildings to reflect away heat; the Mylar film that coats the skins of some spacecraft is also covered in gold foil for the same reason.
The purity of gold is measured in units called karats. Pure gold is 24 karat. An alloy that is 92% gold is 22 carat (92% of 24), 18 carat gold is 75% gold, 12 karat is 50% gold, and so on. Gold in jewelry is often alloyed with silver or copper, with a small amount of zinc to harden it. Gold can be given a range of colors depending on the metal with which it is alloyed: white gold contains 10% nickel, red gold contains 50% copper, blue gold contains 54% indium, purple gold contains 20% aluminum, green gold (also known as electrum) contains 27% silver, and black gold contains 25% cobalt.
In its compounds, gold is usually found in the +1 or +3 oxidation states; Au+ is known as the gold(I) or aurous ion, and Au3+ is known as the gold(III) or auric ion.
Gold salts are used in some treatments for arthritis, when non-steroidal anti-inflammatory drugs do not work. Because there are side effects from having gold build up in the body, this kind of treatment can only be used for a few years. Gold is also used in dentistry to fill cavities and make crowns; the gold is alloyed with silver, palladium, and zinc to harden the amalgam. Over 60 tons of gold per year are used in this fashion.
Roentgenium (Rg, Z=111).
Roentgenium is a synthetic element, produced by the bombardment of bismuth-209 with nickel-64. The longest-lived isotope, roentgenium-280, has a half-life of 3.6 seconds. It was first produced at the GSI in Darmstadt, Germany, in 1994, and was named for Wilhelm Röntgen, the discoverer of X-rays.
Group 2B (12)
The Group 2B elements (Group 12 in the IUPAC designation) have the electron configuration (n-1)d10 ns2. These metals usually form 2+ charges, which is why this group has historically been called 2B (or not 2B, that is the question).
Zinc (Zn, Z=30)
Zinc is a fairly hard, bluish-white metal. The name is derived from the German word for the metal, zink, which may in turn have originated from the Persian word for stone, sing. It is found in the Earth's crust at a concentration of 75 ppm, making it the 24th most abundant element. It is found in the ores sphalerite, zinc blende, or wurtzite [zinc sulfide, ZnS], smithsonite or zinc spar [zinc carbonate, ZnCO3], hemimorphite or calamine [hydrated zinc silicate hydroxide, Zn4Si2O7(OH)2·H2O], hydrozincite or zinc bloom [zinc carbonate hydroxide, Zn5(CO3)2(OH)6], and franklinite [(Fe,Mn,Zn)(Fe,Mn)2O4].
Zinc compounds were known for many thousands of years, and were used in medical treatments. Zinc metal was refined in India as far back as 1300 BC, and was used in making brass by mixing copper with zinc ores such as calamine, but it was not recognized as an element until the mid-1700's.
Zinc tarnishes in the air to form a coating of zinc oxide. It has a low melting point (419°C) and boiling point (907°C). Zinc is malleable between 100°C and 210°C, but above this range, it becomes brittle.
Zinc is the fourth most commonly used metal, after iron, aluminum, and copper. Its main use is used to coat ("galvanize") iron or steel, forming a protective layer which is preferentially oxidized instead of the iron. Since 1982, the US one-cent piece has been made of primarily zinc (about 97.6% of a penny's weight), surrounded by a thin coating of copper (see above for the entry on Copper). Zinc is also used in the manufacture of automotive engine parts and car bodies, electrical equipment, and in the making of brass (an alloy of 67% copper and and 33% zinc). Other zinc alloys include nickel silvers (20% zinc, 60% copper, and 20% nickel) that are often used in tableware, and Prestal (78% zinc, 22% aluminum), which is almost as strong as steel, but easy to mold. Zinc forms the anode component of dry cell and alkaline batteries; although they are not rechargeable, they are still commonly used because they are cheap.
In its compounds, zinc is usually in the +2 oxidation state. Zinc oxide, ZnO, is a white, insoluble powder used in white paints and watercolors, and pharmaceutical ointments, such as diaper rash medications and calamine lotion, a mixture of zinc and iron oxides. Zinc oxide is used in some sunscreens and sunblocks to protect the skin against damaging UV-B rays. Zinc sulfide, ZnS, is used as a white pigment in fluorescent paints, and is combined with barium sulfide to make a white pigment called lithophone; it is also used in scintillation detectors because it emits light when excited by X-rays or electrons. Zinc dichromate, ZnCr2O7, is an orange-red pigment. Zinc chromate, ZnCrO4, is a brilliant yellow pigment.
Zinc is non-toxic, and is an essential nutrient in the diet, because it is used in many proteins and enzymes in the body. A particularly important one is carbonic anhydrase, which is responsible for the transport of carbon dioxide in vertebrates. Foods that are rich in zinc include oysters, red meat, herring, beans, nuts, cheeses, whole grain and whole grain breads, sunflower and pumpkin seeds, maple syrup, and bran.
Cadmium (Cd, Z=48)
Cadmium is a soft, malleable, silvery metal. It names comes from the Greek word cadmia, the ancient Greek name for calamine, a mineral of zinc carbonate (ZnCO3); cadmium was first observed as an impurity in some calamine ores. It is found in the Earth's crust at a concentration of 0.1 ppm, making it the 65th most abundant element. It is found in the ores greenockite [cadmium sulfide, CdS], cadmoselite [cadmium selenide, CdSe], and otavite [cadmium carbonate, CdCO3], but it is usually obtained as a by-product from the mining of zinc ores.
Cadmium is used for electroplating steel, which is especially useful in preventing corrosion in ocean-going vessels, and in the manufacture of bearings. It main use in nickel-cadmium (NiCad) batteries, where it serves as the anode (see also the entry for Nickel above). Cadmium can absorb neutrons, and is used in the control rods that regulate nuclear reactions in fission power plants.
In its compounds, cadmium is usually found in the +2 oxidation state. Cadmium compounds are used in paint pigments to produce a wide variety of intense colors, such as cadmium yellow (cadmium sulfide, CdS) and cadmium red (cadmium selenide, CdSe).
Small amounts of cadmium are can be eliminated by the body, but it can accumulate in the liver and kidneys. Exposure to large amounts of cadmium is toxic, in part because it interferes with the action of zinc-containing enzymes.
Mercury (Hg, Z=80)
Mercury is a very dense, heavy, silver-white metal that is a liquid at room temperature. Mercury is also known as "quicksilver." It is named for the Roman god, Mercury (Hermes in Greek mythology), who was the swift-moving messenger of the gods; the chemical symbol "Hg" is derived from the Latin name for the metal, hydragyrum, "liquid silver." It is found in the Earth's crust at a concentration of 50 ppb, making it the 68th most abundant element. It is found in the ores cinnabar [mercury(II) sulfide, HgS], livingstonite [mercury antimony sulfide, HgSb4S8], and corderoite [Hg3S2Cl2]
In many respect, mercury is an unusual metal. It is the only commonly encountered metal that is a liquid at room temperature, having a melting point of -38.83°C. When frozen, mercury looks and feels like lead. It has a boiling point of 356.73°C, which means that heating mercury compounds strongly can evaporate some of the toxic metal. It also has a very high density, of 13.534 g·cm-3. Mercury is a poor conductor of heat, but a good conductor of electricity. It has a high coefficient of expansion, and expands and contracts even with changes in temperature. This, combined with the fact that it does not adhere to glass much, makes mercury an ideal liquid for measuring devices such as thermometers, barometers, and sphygmomanometers (blood-pressure meters). Mercury forms alloys with a number of metals; these are usually referred to as amalgams.
Mercury compounds, in the form of cinnabar and other ores, have been used for thousands of years. Metallic mercury has been known since at least 1600 BC. Some alchemists believed that mercury was the key to figuring out how to transform base metals into gold, but these investigations proved fruitless (at least from the perspective of actually making gold).
Mercury, in the form of mercury(II) oxide, MgO, is used in small zinc-mercury "button" batteries that are used in hearing aids and other small devices. Mercury is also used in fluorescent lighting, electrical switches, and dental amalgams (usually with silver and tin, although modern amalgams often replace mercury with copper).
In its compounds, mercury is found in the +1 and +2 oxidation states. The mercury(I) or mercurous ion is actually a diatomic ion with a formula of Hg22+, while the mercury(II) or mercuric ion is a monatomic Hg2+ ion. (Zinc and cadmium also can form diatomic univalent cations [i.e., M22+], but the Hg+—Hg+ bond is much stronger than the Zn+—Zn+ bond or the Cd+—Cd+ bonds, and the univalent Zn and Cd cations are not of much importance.)
Mercury(I) chloride, Hg2Cl2, also known as calomel, is a heavy white powder, which used to be used as a diuretic and laxative. It is not very soluble in water, so very little of the mercury is absorbed by the body, but since mercury accumulates in the body, the effects of mercury toxicity can build up after a while. It was also used as a fungicide and insecticide, and as a treatment for syphilis. Mercury(II) sulfide, HgS, also known as vermillion, is found in the minerals cinnabar and metacinnabar. It has a distinct reddish color used in some paint pigments. Some of the pigments found in cave paintings dating back to 30,000 years ago contain mercury(II) sulfide. Thimerosal is a mercury-containing organic compound which is used as a preservative in some vaccines; there have been some concerns about the mercury in this compound being linked to some cases of autism in children, although there isn't much medical evidence for this.
Mercury poisoning results in severe headaches and nausea, vomiting, stomach pains, and diarrhea; over a longer period of time, fatigue, weakness, memory loss, insomnia, depression, and paranoia can result. The phrase "mad as a hatter" (and the character of the Mad Hatter in Alice in Wonderland) is derived from the symptoms of mercury poisoning exhibited by people in the hat-making industry, who used solutions of mercury(II) nitrate dihydrate, Hg(NO3)2·2H2O, to make rabbit and beaver fur into felt. Organic mercury compounds, such as methyl mercury [CH3Hg]+, and dimethyl mercury, (CH3)2Hg, are especially toxic, because they are extremely volatile, and easily penetrate the blood-brain barrier.
Ununbiium (Uub, Z=112).
Ununbiium is a synthetic element, produced by the fusion of an isotope of zinc with an isotope of lead. "Ununbiium" is a temporary, systematic name (literally meaning "1" "1" "2", the atomic number of the element) until the official name is decided upon. The first isotope produced, ununbiium-277, has a half-life of 0.28 milliseconds. It was first produced at the GSI in Darmstadt, Germany, in 1996.
F. Albert Cotton and Geoffrey Wilkinson, Advanced Inorganic Chemistry, 5th ed. New York: John Wiley & Sons, 1988.
John Emsley, The Elements, 3rd edition. Oxford: Clarendon Press, 1998.
John Emsley, Nature's Building Blocks: An A-Z Guide to the Elements. Oxford: Oxford University Press, 2001.
David L. Heiserman, Exploring Chemical Elements and their Compounds. New York: TAB Books, 1992.