The uses of the transition metals are wide and varied. They appear in almost every facet of our day to day life, from electric cabling to decorative door handles to corrosion-resistant alloys. Hence the transition metals are extremely important elements.
SCANDIUM - Sc
Scandium forms 25 ppm of the earth's crust (cf the better known transition metals cobalt at 29 ppm and copper at 68 ppm). Scandium is very widely but thinly distributed (in over 800 minerals). The only mineral containing appreciable amounts of scandium is the rare thortveitite, Sc2Si2O7, found in Norway, which contains 35-40% Sc2O3. But since the metal scandium has no significant uses, this lack of a good ore is no real problem. Scandium can be obtained as a by-product from the processing of uranium ores which contain only about 0.02% Sc2O3, but as large amounts of the uranium ore have to be processed anyway, this is a major source of Scandium. Scandium does have some uses - the iodide is added to mercury vapour lamps which the TV industry use because of the efficient light output and the similarity to the solar spectrum, while trace amount make aluminium alloys very strong (but they become four times as expensive). Isotopes of scandium are also used in crude oil analysis.
TITANIUM - Ti
Titanium forms 0.63% (i.e. 6320 PPM) of the earth's crust and is a very abundant element, 9th of all elements in fact, and second commonest of the transition elements. Titanium has a very low density for a metal, 57% of that of steel, and has good mechanical strength. When alloyed with small quantities of metals such as Al and Sn, the product has the highest strength to weight ratio of any of the engineering metals. Since about 1950 titanium has found uses in the manufacture of gas turbine engines which led to increased production and improvements in the production techniques. Its major uses are still in the aircraft industry, for airframes and engines, but chemical processing and marine equipment is also an important use. TiO2 is the most widely used white pigment in the paint industry, over 3 millions tonnes being used annually. Titanium alloys are also used in hip replacement units and bone implants, due to the unreactive nature of the alloys. From the chemist's point of view, titanium is important for its use as a component of the Ziegler Natta catalysts used in the polymerisation of alkenes. (Many transition metals find uses as catalysts.) World production of Titanium is about 100,000 tonnes p.a..
VANADIUM - V
Vanadium represents about 136 PPM of the earth's crust and is the 19th most abundant element. Over 60 different minerals contain vanadium. It is often recovered as a by product from other processes (such as uranium production) rather than directly produced. An unusual source is as a by-product from Venezuelan and Canadian crude oil. Vanadium has several important uses. It is added to some steels because it reacts with carbon to form V4C3 and disperses to produce a fine grained steel with resistance to wear and is stronger at high temperatures. These steels are widely used for producing springs and high speed tools. Vanadium(V) oxide is the catalyst in the production of SO3 from SO2 in the manufacture of sulphuric acid - the Contact process. (More tonnes of H2SO4 are manufactured annually than other compound.) Annual production of vanadium exceeds 35,000 tonnes p.a.
CHROMIUM - Cr
Chromium is present at a concentration of 122 PPM of the earth, comparable to vanadium and chlorine (126 PPM). The principle ore of chromium is chromite, FeCr2O4, produced mainly in the old USSR, southern Africa where 96% of known reserves are found, and the Philippines. The main use of chromium is in the production of non-ferous alloys, pure chromium having a low ductility at normal temperatures. It also finds many applications in electroplating which is both a decorative and protective process. About 9.5 million tonnes are produced annually.
MANGANESE - Mn
Manganese is the 12th most abundant element, and the third most abundant transition element at 0.106% (1060 PPM) of the earth's crust. Over 300 minerals contain manganese, of which 12 are important commercially. More than 1012 tonnes of "manganese nodules" litter the ocean floor, with 107 tonnes deposited annually. This is due to weathering of rocks which produces colloidal particles of Mo, Fe, and other metal oxides, which agglomerate into lumps in the sea. At 15-30% Mn, it is the presence of other metals which makes these nodules an attractive source of Mn. Of its many uses, one is dominant - 95% of all the manganese ores are used in the production of steel, mainly in the form of ferromanganese. Ores equivalent to 10 million tonnes of MN are produced annually. In the steel furnace, the Mn forms MnS which joins the slag, preventing the formation of FeS which induces brittleness. It also combines with oxygen to prevent the formation of bubbles in the solid metal. Finally it increases the hardness of steel, and is used where resistance to wear and mechanical shock is important e.g. excavators, dredgers, rail crossings etc. It is also used in the production of non ferrous alloys. "Manganin" (84% Cu, 12% Mn, 4% Ni) is used in electrical instruments because the temperature coefficient of its resistivity is almost zero. Many Mn compounds find uses as well. You may have heard of potassium permanganate, KMnO4 for example.(Interestingly, although KMnO4 is very wellknown, the Mn7+ oxidation state it displays is actually very rare indeed.) MnO2 finds extensive use in dry batteries, and is also used in the brick and glass industry, and in the production of MnFe2O4 to make magnets of televisions.
IRON - Fe
Iron is the 4th most abundant element at 6.2% (62000 PPM) after oxygen, silicon, and aluminium, making it the commonest transition metal, and it is one of the most important elements. It is produced on a vast scale in the blast furnace process. Iron finds use in an enormous variety of steels, annual world production being about 700 million tonnes i.e. it is very important economically, and of course its main use is in building things. Iron is the catalyst used in the Haber process to manufacture NH3. (More moles of NH3 are manufactured than any other compound and only H2SO4 is made on a bigger tonnes scale, and both compounds have many uses.)
COBALT - Co
Cobalt is present at 29 PPM i.e. 0.0029% of the earth's crust, is only the thirtieth most abundant element and apart from Sc at 25 PPM, is the rarest of the first row transition elements. Only a few important ores exist although over 200 cobalt containing minerals are known. About 33,000 tonnes are produced annually. About 30% of this is used to produce chemicals for the ceramic and paint industries. Many blue paints contain cobalt compounds. Cobalt compounds are also used as catalysts in the OXO process for the formation of aldehydes, and hydrogenation and dehydrogenation processes are equally important. Another 30% of the cobalt is used in the production of high-temperature alloys in the construction of gas turbines. Many magnetic alloys containing Co are also important e.g. Alnico steel.
NICKEL - Ni
Nickel is the seventh most abundant transition metal and 22nd most abundant element at 99 PPM Over a quarter of the world production of Ni comes from the Sudbury Basin in Canada, a giant meteor crater measuring 17 by 37 miles. Total production of the metal is around 750,000 tonnes. Most is used in the production of alloys, both ferrous and non ferrous. Stainless steel contains up to 8% Ni and it is also used in Alnico steel for strong magnets. Small amounts are used as catalysts for hydrogenation of unsaturated vegetable oils. Nickel is well known as a useful catalyst for hydrogenation and other reactions in the lab and industry, often as the very finely divided form called Raney Nickel.
COPPER - Cu
Copper is present at 68 PPM in the earth's crust and has several important ores, as well as being found native. About 8 million tonnes are produced annually. An important metal, copper's major use is as a conductor of electricity, but it is also used in the formation of coins (money), as well as brass (Cu-Zn), bronze (Cu with Sn) and special alloys like Monel (Ni-Cu)
ZINC - Zn
Zinc is more abundant than copper at 76 PPM, and about 6 million tonnes are produced each year. About 35-40% of this is used as an anti-corrosion coating - e.g. galvanized steel, which is simply steel that has been zinc plated to prevent it rusting. Apart from brasses, several special alloys of zinc are used for diecasting, including the majority of pressure diecastings. Large quantities are used in the manufacture of batteries, and as a roof cladding.