Scandium abundance

Scandium abundances have been measured in stars by spectroscopic interpretation of the 5526 and 5657 A lines of the Sc+ ion, which is isoelectronically similar... 

Scandium is apparently much more abundant (the 23rd most) in the sun and certain stars than on earth (the 50th most abundant). It is widely distributed on earth, occurring in very minute quantities in over 800 mineral species. The blue color of beryl (aquamarine variety) is said to be due to scandium. It occurs as a principal component in the rare mineral thortveihte, found in Scandinavia and Malagasy. It is also found in the residues remaining after the extrachon of tungsten from Zinnwald wolframite, and in wiikite and bazzite. 

Lanthanides is the name given collectively to the fifteen elements, also called the elements, ranging from lanthanum. La, atomic number 57, to lutetium, Lu, atomic number 71. The rare earths comprise lanthanides, yttrium, Y, atomic number 39, and scandium. Sc, atomic number 21. The most abundant member of the rare earths is cerium, Ce, atomic number 58 (see Ceriumand cerium compounds). 

Although scandium is chemically similar to rare-earths, it no longer is considered to be one of them. Scandium is the 42nd most abundant element found in the Earths crust, making up about 0.0025% of the Earths crust. It is widely distributed at 5 ppm on the Earth. (It is about as abundant as lithium, as listed in group 1.) Scandium is even more prevalent in the sun and several other stars than it is on Earth. 

Fig. 8.5. The delicious cocktail of the supernovas. Mixing 13 measures of SNll with 1 measure of SNl, we find a composition of matter that approaches observed abundances in the Solar System. Certain isotopes of chlorine, potassium and scandium, among others, are not produced in snfficient qnantities, however. (From Nomoto et at. 1997.)...

The earth s crust is again a good source of lanthanides. Although the name rare earths is still used to denote the lanthanide elements, and scandium and yttrium, in the strictest sense of the word rare they are more plentiful than many of our common elements. It comes as a surprise to many people when a comparison of the relative abundance of the lanthanides and other elements in the earth s crust is made. Table 4... 

The lanthanides (Ln) include lanthanum (La) and the following fourteen elements—Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu— in which the 4f orbitals are progressively filled. These fifteen elements together with scandium (Sc) and yttrium (Y) are termed the rare-earth metals. The designation of rare earths arises from the fact that these elements were first found in rare minerals and were isolated as oxides (called earths in the early literature). In fact, their occurrence in nature is quite abundant, especially in China, as reserves have been estimated to exceed 84 x 106 tons. In a broader sense, even the actinides (the 5f elements) are sometimes included in the rare-earth family. 

Natural isotopes of scandium and their solar abundances... 

Sc is the only stable isotope of scandium therefore all elemental observations ofits elemental abundance are of the abundance of 45Sc. This isotope has... 

Vanadium is one of the odd-Z elements thathas only a single stable isotope,51V but it has another very rare isotope, 5°V, that is so long lived that it is essentially stable, and a second radioactive isotope for which evidence exists in presolar supernova grains. Vanadium is about six times more abundant than the rare scandium, but it is underabundantrelative to its immediate even-Z neighbors Ti and Cr. Itis the 26th most abundant element. 

When Mendeleev produced his original Periodic Table in 1869, he left a space for a metallic element of atomic mass 44 preceding yttrium. The first fairly pure scandium compounds were isolated by Cleve in 1879, but it was not until 1937 that the element itself was isolated. Although a relatively abundant element, it is fairly evenly distributed in the earth s crust and has no important ores, though it is the main component of the rare ore thortveitite (Sc2Si207), thus being relatively expensive. In fact, it is mainly obtained as a by-product from uranium extraction. 

The abundances of 39 nongaseous elements in the Sun have assigned errors below 30%. Only the four elements sulfur, manganese, scandium, and strontium differ by more than 20% from Cl abundances. The difference is below 10% for 27 of these elements. The agreement between meteoritic and solar abundances must therefore be considered excellent and there is not much room left for further improvements. Obvious candidates for redetermination of solar abundances are manganese and sulfur. The hmiting factor in the accuracy of meteorite abundances is the inherent variability of Cl chondrites, primarily the Orgueil meteorite. 

Davis A. M. and Hinton R. W. (1985) Trace element abundances in OSCAR, a scandium-rich refractory inclusion from the Ornans meteorite. Meteoritics 20, 633 -634. 

The refractory component comprises the elements with the highest condensation temperatures. There are two groups of refractory elements the refractory lithophile elements (RLEs)—aluminum, calcium, titanium, beryllium, scandium, vanadium, strontium, yttrium, zirconium, niobium, barium, REE, hafnium, tantalum, thorium, uranium, plutonium—and the refractory siderophile elements (RSEs)—molybdenum, ruthenium, rhodium, tungsten, rhenium, iridium, platinum, osmium. The refractory component accounts for —5% of the total condensible matter. Variations in refractory element abundances of bulk meteorites reflect the incorporation of variable fractions of a refractory aluminum, calcium-rich component. Ratios among refractory lithophile elements are constant in all types of chondritic meteorites, at least to within —5%. 

Figure 7 shows the abundances of the four refractory lithophile elements—aluminum, calcium, scandium, and vanadium—in several groups of undilferentiated meteorites, the Earth s upper mantle and the Sun. The RLE abundances are divided by magnesium and this ratio is then normalized to the same ratio in Cl-chondrites. These (RLE/Mg)N ratios are plotted in Figure 7 (see also Figure 1). The level of refractory element abundances in bulk chondritic meteorites varies by less than a factor of 2. Carbonaceous chondrites have either Cl-chondritic or higher Al/Mg ratios (and other RLE/Mg ratios), while rumurutiites (highly oxidized chondritic meteorites), ordinary chondrites, acapulcoites, and enstatite chondrites are depleted in refractory elements. The (RLE/Mg)N ratio in the mantle of the Earth is within the range of carbonaceous chondrites.

There are few measurements of the Fe (Fe203) abundance in mantle xenoliths (O Neill et al, 1993 Canil et al., 1994 Canil and O Neill, 1996). Wet chemical determinations for FeaOs in peridotites are fraught with errors, but better and more precise results are obtainable with Moss-bauer spectroscopy of individual minerals (O Neill et al., 1993). Fe " " behaves as a mildly incompatible element during melting with a bulk D of —0.1, similar to that of scandium or V (Figure 12(e)). 

Orthopyroxene partitions nickel, cobalt, and manganese less than olivine and there are no clear correlations amongst these elements. Although low in abundance, orthopyroxene can be a significant reservoir for the trivalent cations vanadium, scandium plus tetravalent titanium, due to its high modal abundance, especially in depleted xenoliths with little or... 

Scandium is a moderately abundant element. However, it tends to be spread out throughout the earth rather than concentrated in a few places. This makes it difficult to isolate. In fact, scandium is classified as a rare earth element. Rare earth elements are not really rare. However, they are difficult to extract from the earth. They were also difficult to separate from each other. 

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