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*Click on the element names below for more details.
The term rare earth is disingenuous as they are neither rare nor earths. The rare earths are more plentiful than silver and some elements (lanthanum, cerium, neodymium and yttrium) are more common than lead. Together rare earth elements represent approximately a sixth of all known elements in the earth's crust (promethium is an exception as it does not occur naturally). Since these elements are of uncommon mineable concentration and the individual elements are difficult to separate, the prices are relatively high. Most rare earth oxides have sharp absorption bands in the visible, ultraviolet and near infrared. This property, associated with the electronic structure gives beautiful pastel colors to many of the rare earth salts. Monazite and Bastnasite are the two principal commercial sources of rare metals. Lanthanum (La, atomic number 57) was isolated in a relatively pure form in 1923. Ion exchange and solvent extraction techniques have led to much easier isolation of the rare earth elements. Lanthanum is one of the most reactive of the rare-earth metals; it is the prototype for the lanthanide series. It is silvery white, malleable, ductile and so soft it can be cut with a knife. It oxidizes rapidly when exposed to air. Cold water attacks lanthanum slowly, and hot water attacks it much more rapidly. The metal reacts directly with elemental carbon, nitrogen, boron, selenium, silicon, phosphorus, sulphur and with halogens. Lanthanum is found in rare earth minerals such as cerite, monazite, allanite and bastnasite. Monazite and bastnasite are principal ores in which lanthanum occurs in percentages up to 25% and 38% respectively. Some uses of rare earth compounds containing lanthanum are as follows:
Cerium (Ce, atomic number 58) - the element was discovered in 1803 by Klaproth and also by Berzelius and Hisinger. The metal was first prepared in 1875 by Hillebrand and Norton. Cerium is the most abundant of the rare earth metals. It is found in the following minerals: allanite (also known as orthite), monazite, bastnasite, cerite and samarskite. Monazite and bastnasite are the more important known sources of cerium at present. Cerium is the second most reactive metal in the lanthanide series, Europium being the most reactive. Cerium composes slowly in cold water and rapidly in hot water. Alkali solutions and both dilute and concentrated acids attack the metal rapidly. The metal in pure form is likely to ignite if struck. Once struck, tiny pieces of cerium are knocked off and once air born they burst into flame by reacting quickly with oxygen (heats up and burst into flame). Some uses of cerium are as follows:
Praseodymium (Pr, atomic number 59) was discovered when von Welsbach separated didymia into two other, praseodymium and neodymia, which gave salts of different colors. Compounds of these elements (and other rare earth elements) in solution have distinctive sharp spectral absorption bands or lines. Praseodymium occurs along with other rare earth elements in a variety of minerals including Monazite and Bastnasite. Praseodymium is soft, silvery, malleable and ductile. It develops a green oxide coating that falls off when exposed to air. Like other REM, it should be kept under a light mineral oil or in sealed plastic. It can be prepared by several different methods, such as by calcium reduction of the anhydrous chloride of fluoride. Praseodymium uses are as follows:
Neodymium (Nd, atomic number 60) - von Welsbach separated didymium into two new elemental components, neodymia and praseodymia, by repeated fractionation of ammonium didymium nitrate in 1885. It wasn't until 1925 when neodymium was separated into a relatively pure form. It is found in misch metal (comprises 18%). It is also found in minerals such as monazite and bastnasite (the most common sources for rare earth metals). Neodymium can be refined by separating neodymium salts from other rare earths by ion-exchange or solvent extraction. Neodymium metal has a bright silvery metallic luster. It is one of the more reactive rare earth metals (REM's) and quickly tarnishes in air forming an oxide that spalls off and exposes metal to oxidation. To prevent this from occurring, neodymium should be kept under light mineral oil or sealed in a plastic material. The demand for neodymium is extremely high. Some of neodymium's uses are as follows:
Promethium (Pm, atomic number 61) was not identified until 1945 when Marinsky, Glendenin and Coryell made the first chemical identification by use of ion-exchange chromatography. Their work was done by fission of uranium and by neutron bombardment of neodymium. In 1902 Branner predicted the existence of an element between neodymium and samarium. This theory was confirmed by Moseley in 1914. It wasn't until 1941 that staff at Ohio State University irradiated neodymium and praseodymium with neutrons, deuterons and alpha particles producing several new radio- activities (which most likely were those of element 61). Wu and Segre, and Bethe confirmed the formation in 1942, however, chemical proof of element 61 was lacking because of the difficulty in separating the rare earths from each other at that time. Promethium is highly radioactive; there is not a lot of it. The only rare earth element that is radioactive and it is not found in nature. It is from the decay of other radioactive elements. Nuclear research discovered promethium. It is a soft beta emitter (although no gamma rays are emitted) X-radiation can be generated when beta particles are impinged on elements of high atomic number and great care must be taken when handling it. Promethium salts luminesce in the dark with a pale blue or greenish glow due to their radioactivity. Little is known about the properties of metallic promethium. Two allotropic modifications exist. Uses for promethium are as follows:
Samarium (Sm, atomic number 62) was discovered spectroscopically by its sharp absorption lines in 1879 by Lecoq de Boisbaudran in the mineral samarskite. Samarium is found along with other members of the rare earth elements in many minerals including the common sources, monazite and bastnasite. It occurs in monazite to the extent of 2.8%. While misch metal containing 1% of samarium metal has long been used, samarium has not been isolated in relatively pure form until recently. Ion-exchange and solvent extraction techniques have recently simplified separation of the rare earths form one another. More recently, electrochemical deposition, which uses an electrolytic solution of lithium citrate and a mercury electrode, is said to be a simple and highly specific way to separate the rare earths. Samarium metal can be produced by reducing the oxide with lanthanum. Samarium has a bright silver luster and is reasonably stable in air. Three crystal modifications of the metal exists with transformations at 734 and 922 degrees Celsius. The metal ignites in air at approximately 150 degrees Celsius. The sulfide has excellent high temperature stability and good thermoelectric efficiencies up to 11pp degrees Celsius. Samarium changes oxidation stages very easily. Some uses for Samarium are as follows:
Europium (Eu, atomic number 63) was discovered in the form of spectral lines that were not accounted for by samarium or gadolinium concentrates in 1890 by Boisbaudran. The official discovery of europium is generally credited to Demarcay who separated the rare earth in reasonably pure form in 1901. The pure metal was not isolated until recent years. Europium is now prepared by mixing Eu203 with a 10% excess of lanthanum metal and heating the mixture in a tantalum crucible under high vacuum. The element is collected as a silvery white metallic deposit on the walls of the crucible. As with other rare earth metals (with the exception of lanthanum), europium ignites in air at about 150 to 180 degrees Celsius. Europium is about as hard as lead and is quite ductile. It is the most reactive of the rare earth metals, it quickly oxidizes in air. It resembles calcium in its reaction to water. Bastnasite and monazite are the principal ores containing europium. Europium has been identified spectroscopy in the sun and certain stars. Some known uses for Europium are as follows:
Gadolinium (Gd, atomic number 64) rare earth metal is obtained from the mineral gadolinite. Gadolinia, the oxide of gadolinium, was separated by Merignac in 1880 and Lecoq de Boisbaudran independently isolated it from Mosasander's yttria in 1886. Gadolinium is found in several other minerals, including monazite and bastnasite. With the development of ion-exchange and solvent extraction techniques, the availability and the prices of gadolinium and the other rare earth metals have greatly improved. The metal can be prepared by the reduction of the anhydrous fluoride with metallic calcium. Gadolinium is silvery white, has a metallic luster and is malleable and ductile (like other related rare earth metals). At room temperature gadolinium crystallizes in the hexagonal, close packed alpha form. Upon heating to 1235 degrees Celsius, alpha gadolinium transforms into the beta form (which has a body centered cubic structure). The metal is relatively stable in dry air but tarnishes in moist air. It forms a loosely adhering oxide film which falls off and exposes more surface to oxidation. The metal reacts slowly with water and is soluble in dilute acid. Gadolinium has the highest thermal neutron capture cross-section of any known element (49,000 barns). Some known uses for Gadolinium are as follows:
Terbium (Tb, atomic number 65) was discovered by Mosander in 1843. Terbium is found in cerite, gadolinite and other minerals along with other rare earths. It is also recovered from monazite in which it is present to the extent of 0.03%, from xenotime and from euxnite (a complex oxide containing 1% more of terbia). Terbium has been isolated only in recent years with the development of ion exchange techniques for separating the rare earth elements. As with other rare earth metals; terbium can be produced by reducing the anhydrous chloride or fluoride with calcium metal in a tatalum crucible. Calcium and tantalum impurities can be removed by vacuum re-melting. Other methods of isolation are also possible. Terbium is reasonably stable in air. It is a silver grey metal which is malleable, ductile and soft enough to be cut with a knife. Two crystal modifications exist with a transformation temperature of 1289 degrees Celsius. The oxide is a chocolate or dark maroon color. Some known uses of Terbium are as follows:
Dysprosium (Dy, atomic number 66) was discovered in 1886 by Lecoq de Boisbaudran, but not isolated. The oxide and metal wasn't available in relative pure form until 1950 when development of ion exchange separation and metallographic reduction techniques were created by Spedding and associates. Dysprosium occurs along with other rare earths in a variety of minerals such as: xenotime, fergusonite, gadolinite, euxenite, polycrase and blomstrandine. Monazite and bastnasite are the most important sources. Dysprosium can be prepared by reduction of the trifluoride with calcium. The metal is a metallic bright silver luster. Dysprosium is relatively stable in air temperature and is readily attacked and dissolved by dilute and concentrated mineral acids to evolve hydrogen. The metal is soft enough to be cut with a knife and can be machined without sparking if overheating is avoided. Small amounts of impurities can greatly affect its physical properties. Dysprosium is very reactive and therefore is stored in foil. Its thermal neutron absorption cross section and high melting point suggest metallurgical uses in nuclear control applications for alloying with special stainless steels. Some known uses for dysprosium are as follows:
Holmium (Ho, atomic number 67).The special absorption bands of holmium were noticed in 1878 by the Swiss chemists Delafontaine and Soret, who announce the existence of an "Element X". Cleve, of Sweden, later independently discovered the element while working on erbia earth. The element is name is therefore name after Cleve's native city. Holmia, the yellow oxide, was prepared by Homberg in 1911. Holmium occurs in gadolinite, monazite and in other rare earth minerals. It has been isolated by the reduction of its anhydrous chloride or fluoride with calcium metal. Pure holmium has a metallic to bright silver luster. It is relatively soft and malleable, it is able to stay dry in room temperature, but it rapidly oxidizes in moist air and at elevated temperatures. Holmium metal has unusual magnetic properties. It has the highest magnetic moment of any known element in the periodic table. It has the greatest number of impaired electrons and impaired electrons are what give rise to magnetism. Therefore, Holmium has many uses in magnetic materials. Very few other uses have been found for the element. Like some other rare earths Holmium seems to have a low acute toxic rating. Some known uses for Holmium are as follows:
Erbium (Er, atomic number 68) is found in minerals that dysprosium is found in (xenotime, fergusonite, gadolinite, euxenite, polycrase and blomstrandine). In 1842, Mosander separated "yttria" found in the mineral gadolinite, into three fractions. He called these three fractions: yttria, erbia and terbia. After 1877, the earlier known erbia became terbia. The erbia of this period was later shown to consist of five oxides, now known as: erbia, Scandia, holmia, thulia and ytterbia. By 1905 Urbain and James independently succeeded in isolating fairly pure Er2O3. Klemm and Bommer first produced reasonable pure erbium metal in 1934 by reducing the anhydrous chloride with potassium vapor. The pure metal is soft and malleable and has a bright, silvery, metallic luster. As with other rare earth metals, it's properties depend, to a certain extent, on the impurities present. The metal is fairly stable in air and does not oxidize as rapidly as some of the other metals. Some known uses for erbium are as follows:
Thulium (Tm, atomic number 69) was discovered in 1879 by Cleve Thulium occurs in small quantities along with other rare earths in a number of minerals. It is obtained commercially from monazite which contains about 0.007% of the element. Thulium is the least abundant of the rare earth elements, but with new sources recently discovered, it is now considered to be about as rare as silver, gold or calcium. Thulium is very difficult to separate from the other elements because it is so similar in size. It can be isolated by reduction of the oxide with lanthanum metal or by calcium reduction of a closed container. The element is silver/grey, soft, malleable and ductile. It can be cut with a knife. Due to the difficulty to separate it is very expensive and is not used often. It has a +2 and +3 oxidation state. Chemists are beginning to find uses for it and uses should increase in years to come. As with other lanthanides, thulium has a low to moderate acute toxic rating. It should be handled with care. The few known uses for Thulium are as follows:
Ytterbium (Yb, atomic number 70) - Marignac discovered a new component in the earth then known as erbia in 1878 which he called ytterbia. In 1907, Urbain separated ytterbia into two components which he called neoytterbia and lutecia. The elements in these earths are now knows as ytterbium and lutetium, respectively. These elements are identical with aldebaranium and cassiopeium (discovered independently and at about the same time by von Welsbach). Ytterbium occurs along with other rare earths in a number of rare minerals. The element was first prepared by Klemm and Bonner in 1937 by reducing ytterbium tri-chloride with potassium. Their metal was mixed, however, with KCI. Daane, Dennison and Spedding prepared a much purer form in 1953 from which the chemical and physical properties of the element could be determined. It is commercially recovered principally from monazite sand which contains about 0.03%. Ion-exchange and solvent extraction techniques developed in recent years have greatly simplified the separation of the rare earths from one another. Ytterbium is a silvery and lustrous metal that is very soft and reacts very rapidly with oxygen. Even though the element is fairly stable, it should be kept in closed containers to protect it from air to moisture. Ytterbium is readily attacked and dissolved by dilute and concentrated mineral acids and reacts slowly with water. Ytterbium is the least abundant amongst the rare earths. Its chemistry is the least understood therefore it is not used often. Ytterbium has some possible uses, they are as follows:
Lutetium (Lu, atomic number 71) - In 1907, Urbain described a process by which Marignac's ytterbium (1879) could be separated into the two elements, ytterbium (neoytterbium) and lutetium. These elements were identical with "aldebaranium" and "cassiopeium", independently discovered at this time. The spelling of the element was changed from lutecium to lutetium in 1949. Lutetium occurs in very small amounts in nearly all minerals containing yttrium and is present in monazite to the extent of about 0.003% which is commercial source. The pure metal has been isolated only in recent years and is one of the most difficult to prepare. It can be prepared by the reduction of the anhydrous LuCl3 or LuF3 by an alkaline earth metal. The metal is silvery white and relatively stable in air. 176Lu occurs naturally (2.6%) with 175 Lu (97.4%). It is radioactive with a half-life of about 3 x 10 10 years. Some known uses for Lutetium are as follows:
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Periodic Table of REE Videos
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