The Rare-Earth Elements

XVich stores of the rare earth minerals lay hidden for centuries m the Scandinavian peninsula until, one day in 1787, Lieutenant Carl Axel Arrhenius found, near the Ytterby feldspar quarry in Roslagen, an unusual black rock which he at first called ytterite, but which was later named gadolinite for the famous Finnish scientist Johan Gadolin who detected in it yttria, scandia, and all the rare earths of the yttria group. 

The interruptions of army life were never able to stifle Arrhenius s love of science, and he always regretted that he had been snatched away so early from his studies and thrust into the occupations of practical life (69). In the school year 1816-17, when he was about sixty years old, he studied chemistry in Beizelius laboratory. Almost to the close of his life he continued to attend Berzelius lectures. Even the disconnected words which Arrhenius uttered during the delirium of his last illness showed that his mind was still occupied with mmeralogical chemistry (69). 

The first description of gadolinite was published by Bengt Reinhold Geijer (1758-1815) in Ctell s Annalen in 1788. I am now sending you, said he, a specimen of a heavy stone which one of my friends, Hr. Lieut. Arrhenius, found. It was discovered at Ytterby, three miles from Stock- 

Johan Gadolin, 1760-1852. Professor of chemistry at the University of Abo, Finland. Discoverer of the complex earth yttria, which afterward yielded an entire senes of simple oxides He made a thorough study of tire rare earth minerals from Ytterby, Sweden 

In 1812 Thomas Thomson visited the Ytterby quariy. It would be improper, said he, while giving an account of the minerals of Upland, to pass by the quarry of Ytterby, become famous from the curious substances that have been found in it It lies rather less than two English miles north from the fortress of Vaxholm, and consists of a rock obviously connected with gneiss, that constitutes the basis of the country though it consists chiefly of beautiful white felspar, and felspar of a flesh red 

Indicate the position of the rare-earth elements in Mendeleev s periodic table, the electron configurations and sizes of their atoms, and their oxidation states. 

Large chemical isomer shifts are also observed in some instances, but less correlation has been done in this area. 

The detailed Hamiltonians appropriate to the electronic and nuclear properties of the rare earths in general have been excellently summarised elsewhere [1]. They are not given here explicitly because of the more limited depth of treatment. Note, however, that the vectorial addition of the total orbital, L, and spin angular momentum, S, denoted by J is the most useful quantum number for describing electronic states. Any crystalline field potential then acts as a perturbation to the appropriate / state. This is opposite to the situation found in Fe, where the crystalline field is the dominant term. 

The high energy of the 145-43-keV transition in Pr is not conducive to a strong Mdssbauer resonance and indeed the first attempts to observe it 

The 67-25-keV and 72-5-keV resonances in Nd were first observed by Kaindl and Mossbauer in 1968 [4], Both levels are populated by the decay of 

17-7-y (Fg. 17.1). This can be prepared by the reaction sequence (EC 340 d) Pm with ion-exchange separation of the from the samarium after a suitable lapse of time ( 6 months). A satisfactory source matrix can be made from NdaOa doped with the Pm, and all data have been obtained at 4-2 K. 

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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 earths, it can be produced by reducing the anhydrous chloride or fluoride with calcium metal in a tantalum crucible. Calcium and tantalum impurities can be removed by vacuum remelting. Other methods of isolation are possible. 

Figure 47.6). By choosing which isotope to mea.sure, all of the rare earth elements can be analyzed accurately and quickly following their ion-exchange separation into just two fractions. 

Comparing the relative abundance of the rare earths and the other elements Hsted in Table 1, the rare earths are not so rare. Cerium, the most abundant of the rare-earth elements is roughly as abundant as tin thuHum, the least abundant, is more common than cadmium or silver. Over 200... 

Laser isotope separation techniques have been demonstrated for many elements, including hydrogen, boron, carbon, nitrogen, oxygen, sHicon, sulfur, chlorine, titanium, selenium, bromine, molybdenum, barium, osmium, mercury, and some of the rare-earth elements. The most significant separation involves uranium, separating uranium-235 [15117-96-1], from uranium-238 [7440-61-1], (see Uranium and uranium compounds). The... 

Inductively coupled plasma-mass spectrometry (ICP-MS) is a multielement analytical method with detection limits which are, for many trace elements, including the rare earth elements, better than those of most conventional techniques. With increasing availability of ICP-MS instalments in geological laboratories this method has been established as the most prominent technique for the determination of a large number of minor and trace elements in geological samples. 

Structure and morphology. Most of the rare-earth elements were encapsulated in multilayered graphitic cages, being in the form of single-domain carbides. The carbides encapsulated were in the phase of RC2 (R stands for rare-earth elements) except for Sc, for which Sc3C4(20] was encapsulated[21]. 

Figure 4 shows vapor pressure curves of rare-earth metals[24], clearly showing that there is a wide gap between Tm and Dy in the vapor pressure-temperature curves and that the rare-earth elements are classified into two groups according to their volatility (viz.. Sc, Y, La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, and Lu, non-volatile elements, and Sm, Eu, Tm, and Yb, volatile elements). Good correlation between the volatility and the encapsulation of metals was recently... 

B. Jezowska-Trzebiatowska, S. Kopacz and T. Mikul-SKl, The Rare Earth Elements, Occurrence and Technology, Elsevier, Amsterdam, 1990, 540 pp. 

According to this assignment the differentiating electron, that is, the final electron to enter the atom of lutetium, wss seen as an f electron. This suggested that lutetium should be the final element in the first row of the rare earth elements, in which f electrons are progressively filled, and not a transition element as had been believed by the chemists. As a result of more recent spectroscopic experiments the configuration of ytterbium has been altered to (27)... 

The problem is no longer the validity of Mendeleev s system, but the best way to represent it. Should it be the original short-form table with 8 columns, the familiar medium-long form with 18 columns, or perhaps even a long-form table with 32 columns, which more naturally accommodates the rare earth elements Into the main body of the table Altanahvely, some favor pyramidal tables, while others advocate the left-step form proposed by diaries Janet in the 1920s. Theodor Benfey and rhilip Stewart have proposed continuous spiral models. Hundreds, possibly even thousands, of periodic systems have been proposed, and each has its ardent supporters. 

C5. Craven, W. E., "Intercalation of the Rare Earth Elements into Graphite and Di-chalcogenides, M. S. Thesis, U S Air Force Institute of Technology, Air University, 1965, 68 pp. Wright-Patterson Air Force Base, Ohio. 

Almost all of the rare-earth metal/rare-earth metal tri-iodide systems, R/RI3, contain binary phases with the rare-earth element in an oxidation state lower than -1-3 ( reduced rare-earth metal iodides) [3, 7, 10-13]. More common is the oxidation state -i-2. Elements that form di-iodides RI2 are illustrated in Fig. 4.1. 

In each of the composition diagrams in Fig. 14.2, the numbers represent a series of reactions run at a defined composition and temperature. These are isometric sulfur slices through three-dimensional K/P/RE/S quaternary phase diagrams. As just one example of what we have studied. Table 14.1 identifies the compositions at each point and the resulting phase(s). We have rigorously studied how phase formation is dependent upon the compositions of reactions for the rare-earth elements Y, Eu, and La and we have also discovered key structural relationships between the rare-earth elements, indicating a significant dependence on rare-earth and alkali-metal size for sulfides and selenides. 

In each representation, the alkali metal is black, the rare-earth element is shaded medium grey, the main group element is dark grey, and selenium is light grey (a) NagEu2(Si2Se6)2,... 

The rare earth elements (R) are those from atomic numbers 57-71, emanating as a particular series from the parent element lanthanum (atomic no. 57). The set of 14 elements from cerium (58) through lutetium (71) inclusive are commonly known as the lanthanoid (or lanthanide Ln) series. The rare earths form a bridge at the... 

Bence, A.E. (1983) Volcanogenic massive sulfides rtx k/water interactions in ba.saltic systems and their effects on the distribution of the rare earth elements and selected first. series transition elements (abst.). 4th International Symposium on Water-Rock interaction, Mi.sasa, Japan, 48. 

Ruhlin, D.E. and Owen, R.M. (1986) The rare earth element geochemistry of hydrothermal sediments from the East Pacific Rise Examination of a seawater scavenging mechanism. Geochim. Cosmochim. Acta, 50, 393-400. 

Hsi C, Langmuir D (1985) Adsorphon of uranyl onto ferric oxyhydroxides applications of the surface complexation site-binding model. Geochim Cosmochim Acta 49 1931-1941 Ingri J, Widerlund A, Land M, Gustafsson O, Anderson P, Ohlander B (2000) Temporal variation in the fractionation of the rare earth elements in a boreal river the role of colloidal particles. Chem Geol 166 23-45... 

Today, ICP-AES is an indispensable inorganic analytical tool. However, because of the high plasma temperature, ICP-AES suffers from some severe spectral interferences caused by line-rich spectra of concomitant matrix elements such as Fe, Al, Ca, Ni, V, Mo and the rare-earth elements. This is at variance with AAS. The spectral interference can of course be minimised by using a (costly) high-resolution spectrometer. On the other hand, the high temperature of the ICP has the advantage of reducing chemical interferences, which can be a problem in AAS. 

Weang ZC, Wang LS (1997) Thermodynamic properties of the rare earth element vapor complexes LnAl3Cl12 from Ln = La to Lu. Inorg Chem 36(8) 1536-1540... 

Other f-transition metal catalysts have been described by von Dohlen (4) and Throckmorton (5) as well as by Chinese (6, 7) and Italian (8-10) scientists. They generally consist of a rare earth compound, an aluminum alkyl, and a halide, the halogens being bound to the rare earth element or aluminum. 

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