Rare earth elements ionic radius

Van Orman JA, Grove TL, Shimizu N (2001) Rare earth element diffusion in diopside influence of temperature, pressure and ionic radius, and an elastic model for diffusion in silicates. Contrib Mineral Petrol 141 687-703... 

Goldschmidt (1923) was the first to note that ionic radii vary as a function of coordination number—i.e., with the number of first neighbors surrounding the ion. The observed variation is fundamentally identical for all cations and, in the case of cations coordinated by anionic ligands, results in a progressive increase in ionic radius with increasing coordination number. As an example, figure 1.9 shows the increases in ionic radius for the various rare earth elements (and In, and Sc ) as a function of coordination number with. ... 

Symbol Ho atomic number 67 atomic weight 164.93 a lanthanide series rare earth element electron configuration [Xe]4/ii6s2 valence state +3 metallic radius (coordination number 12) 1.767A atomic volume 18.78 cc/mol ionic radius Ho3+ 0.894A one naturally occurring isotope. Ho-165. 

Ionic radius Dy,+ 0.908 A. Metallic radius 1.775 A. First ionization potential 5.93 eV second 11.67 eV. Dysprosium appears to he exclusively trivalcnt. Other important physical properties of dysprosium arc given under Rare-Earth Elements and Metals. 

Ionic radius, Pr3+ 1.01 A, Pr 1+ 0.90 A. Metallic radius, 1.828 A. First ionization potential, 5.42 cV second, 10.55 cV. Other important physical piopeities of piaseodymium me given undei Rare-Earth Elements and Metals. 

Ionic radius 0,98 A. Other important physical properties of promethium are given under Rare-Earth Elements and Metals. 

Although the rare-earth elements (REEs) have similar geochemical behavior, since they are all large-ion lithophile elements and most of them partition among melts and mineral phases as a smooth function of ionic radius (with the exception of europium, which, commonly being... 

The lanthanide or rare earth elements (atomic numbers 57 through 71) typically add electrons to the 4f orbitals as the atomic number increases, but lanthanum (4f°) is usually considered a lanthanide. Scandium and yttrium are also chemically similar to lanthanides. Lanthanide chemistry is typically that of + 3 cations, and as the atomic number increases, there is a decrease in radius for each lanthanide, known as the lanthanide contraction. Because bonding within the lanthanide series is usually predominantly ionic, the lanthanide contraction often determines the differences in properties of lanthanide compounds and ions. Lanthanide compounds often have high coordination numbers between 6 and 12. see also Cerium Dysprosium Erbium Europium Gadolinium Holmium Lanthanum Lutetium Praseodymium Promethium Samarium Terbium Thulium Ytterbium. 

The rare earth elements (REE) are the most useful of all trace elements and REE studies have important applications in igneous, sedimentary and metamorphic petrology. The REE comprise the series of metals with atomic numbers 57 to 71 — La to Lu (Table 4.4). In addition, the element Y with an ionic radius similar to that of the REE Ho is sometimes included. Typically the low-atomic-number members of the series are termed the light rare earths (LREE), those with the higher atomic... 

Also as a result of the lanthanide contraction, yttrium has an ionic radius comparable to that of the heavier REE species in the holmium-erbium region. If the effective ionic radius (Shannon 1976) of is plotted (0.90 A)., it plots in between element 67 (Ho) and 68 (Er). Scandium (effective ionic radius is 0.745 A), plots outside of the Lanthanide series. As also the outermost electronic arrangement of yttrium is similar to the heavy rare earths, the element behaves chemically like the heavy rare earths. It concentrates during (geo)chemical processes with the heavier REEs, and is difhcult to separate from the heavy REEs. Scandium, on the other hand, has a much smaller atomic radius, and the trivalent ionic size is much smaller than that of the heavy rare earths. Therefore, scandium does not occur in rare earth minerals, and in general has a chemical behavior that is significantiy different from the other rare earth elements (Gupta and Krishnamurthy 2005). 

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