Rare earth elements properties

Table 1 Selected rare earth element properties ...

Unusual for the cyclopolyene compounds of rare earth elements properties of cyclopentadienyl and indenyl Ce(lV) complexes described in the papers of Indian researchers have prompted Deacon and coworkers [21] to repeat the synthesis of Cp4Ce and its derivatives. They have established [21] that the reaction of (C5H5NH)2-CeCl with CpNa does not lead to tetracyclopentadienide of cerium but to the well known trivalent derivative Cp3Ce under the conditions given in paper [1]. The attempts to reproduce the synthesis of tetrafluorenylcerium and dichloride of dicyclo-heptatrienylcerium failed as well [22]. 

Ion-exchange and complexing properties of organosilicon adsorbents were studied on the example of 50 elements of Periodical System. Among synthesized adsorbents it was found an effective complexation afents toward rare-earth elements. The sorption of elements is accompanied by bright display of tetradic effect. Adsorbents were synthesized, which opened wide chances of soi ption isolation and division of rare-earth elements. 

T.T. Bakumenko, Catalytical properties of rare and rare-earth elements, AN USSR, Kiev, 1963 (in Russian). 

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... 

The two rare earth elements niobium (Nb) and tantalum (Ta) were the main subject of study in the investigation referred to. Both elements have very similar properties and almost always occur together in our solar system. However, the silicate crust of the Earth contains around 30% less niobium (compared to its sister tantalum). Where are the missing 30% of niobium They must be in the Earth s FeNi core. It is known that the metallic core can only take up niobium under huge pressures, and the conditions necessary for this may have been present on Earth. Analyses of meteorites from the asteroid belt and from Mars show that these do not have a niobium deficit. 

Schweitzer, G. K. (1956). The radiocolloid properties of the rare earth elements, page 31 in Rare Earths in Biochemical and Medical Research A Conference Sponspored by the Medical Division, Oak Ridge Institute of Nuclear Studies, October 1955, Report No. ORINS-12, Kyker, G. C. and Anderson, E. B., Eds. (Office of Technical Services, Washington). 

Basic chrome sulfate, 6 543 Basic copper chromate, molecular formula, properties, and uses, 6 561t Basic detergents, 15 222 Basic (cationic) dyes, 9 217, 242-243 anthraquinone, 9 301 azo, 9 421 24 Basic dyestuffs, 9 224 Basic extractants, of rare-earth elements, 14 642... 

Schumm, R. H. Wagman, D. D. Bailey, S. Evans, W. H. Parker, V. B. "Selected Values of Thermodynamic Properties. Table for the Lanthanide (Rare Earth) Elements (Elements 62 through 76 in the Standard Order of Arrangement)" Nat. Bur. Stand. Tech. Note No. 270-7, April 1973. 

Due to the great similarity of the chemical properties of the rare earth elements, their separation represented, especially in the past, one of the most difficult problems in metallic chemistry. Two principal types of process are available for the extraction of rare earth elements (i) solid-liquid systems using fractional precipitation, crystallization or ion exchange (ii) liquid-liquid systems using solvent extraction. The rare earth metals are produced by metallothermic reduction (high purity metals are obtained) and by molten electrolysis. 

The morning session was devoted to a general explanation of the areas of application in studying magnetic properties, oxidation states, compounds, and metal structure. In the afternoon, reviews of the Mossbauer investigations of iron, tin, iodine, tellurium, and some of the rare earth elements were presented. The meeting concluded with a discussion on the future of Mossbauer Spectroscopy in which an interested audience participated. 

The basis for the claim of discovery of an element has varied over the centuries. The method of discovery of the chemical elements in the late eightenth and the early nineteenth centuries used the properties of the new sustances, their separability, the colors of their compounds, the shapes of their crystals and their reactivity to determine the existence of new elements. In those early days, atomic weight values were not available, and there was no spectral analysis that would later be supplied by arc, spark, absorption, phosphorescent or x-ray spectra. Also in those days, there were many claims, e.g., the discovery of certain rare earth elements of the lanthanide series, which involved the discovery of a mineral ore, from which an element was later extracted. The honor of discovery has often been accorded not to the person who first isolated the element but to the person who discovered the original mineral itself, even when the ore was impure and that ore actually contained many elements. The reason for this is that in the case of these rare earth elements, the earth now refers to oxides of a metal not to the metal itself This fact was not realized at the time of their discovery, until the English chemist Humphry Davy showed that earths were compounds of oxygen and metals in 1808. 

The discovery of the rare earth elements provide a long history of almost two hundred years of trial and error in the claims of element discovery starting before the time of Dalton s theory of the atom and determination of atomic weight values, Mendeleev s periodic table, the advent of optical spectroscopy, Bohr s theory of the electronic structure of atoms and Moseley s x-ray detection method for atomic number determination. The fact that the similarity in the chemical properties of the rare earth elements make them especially difficult to chemically isolate led to a situation where many mixtures of elements were being mistaken for elemental species. As a result, atomic weight values were not nearly as useful because the lack of separation meant that additional elements would still be present within an oxide and lead to inaccurate atomic weight values. Very pure rare earth samples did not become a reality until the mid twentieth century. 

Scandium is a soft, lightweight, silvery-white metal that does not tarnish in air, but over time, it turns yellowish-pink. It resists corrosion. Scandium reacts vigorously with acids, but not water. Scandium has some properties similar to the rare-earth elements. Although its position in group 3 places it at the head of the 17 elements of the lanthanide series of rare-earth metals, scandium, as a metal, is not usually considered a rare-earth. Scandiums melting point is l,54l°C, its boiling point is 2836°C, and its density is 2.989 glctn . 

The elements in the lanthanide series are also called rare-earth elements they are not scarce or rare, but at one time they were thought to be rare because they were very difficult to find and extract from their ores, difficult to separate from each other, and difficult to identify. Chemical elements that have similar physical and chemical properties tend to occur together in the same ores and minerals. 

The Rare Earth Elements (REE-Lanthanides and Y) are commonly used to unravel rock-forming processes because of their simiiar chemicai properties, typicaiiy iow soiubiiities and assumed resistance to fractionation in crustai and surface environments. However, under some weathering conditions REE are significantiy mobiiised and fractionated (e.g., Nesbitt 1979 Duddy 1980 Sharma Rajamani 2000). 

Because Sm and Nd are both rare Earth elements and have similar chemical properties, and because they often occupy crystalline sites that are not easily altered, this system is resistant to alteration by later events (such as a later metamorphic event). Hence, this system is often applied to determine old and formation ages, whereas other systems (such as K-Ar) may be applied to obtain metamorphic ages. 

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