Thermodynamics of the lanthanides, chemical

Current interest in high temperature chemistry and the closely related thermodynamics of the actinides will provide additional stimuli for determining precise thermodynamic data in cryogenic as well as in higher temperature regions. The utopian era in the chemical thermodynamics of the lanthanides is sufficiently far off to occasion extension of shrewdly devised schemes to other classes of compounds. Use of the semi-empirical schemes already discussed—or theoretically based ones— plus the key compound concept may prove as effective here (desipte magnetic and electronic complications) as it has for hydrocarbon thermodynamics. 

Westrum, E.F.Jr., Developments in Chemical Thermodynamics of the Lanthanides, in Advances in Chemistry Series, Number 71, American Chemical Society 1967, pp. 25-50. 

The results obtained are also useful in correlating the thermodynamic properties of the chemical compounds of the lanthanides (Brewer, 1971a,b). 

The lanthanide higher oxides have not only peculiar thermodynamic properties, but also unique physical and chemical properties. The physical and chemical properties are presented as a macroscopic parameter, such as the electrical conductivity, the coefficient of expansion, and the conversion rate of a catalysis process. Due to the lack of knowledge of the wide range of non-stoichiometry of the oxygen-deficient fluorite-related homologous series of the lanthanide higher oxides, the macroscopically measured data of the physical and chemical properties are scattered, and therefore, based on the structural principle of the module ideas a deep understanding the relationship between the properties and structures is needed. 

Lanthanide (III) Oxides. The lanthanide(III) oxides will be used to illustrate the present breadth of our most extensive knowledge of the chemical thermodynamics of lanthanide compounds. Cryogenic heat capacities of hexagonal (III) lanthanum, neodymium, and samarium oxides, together with those of cubic (III) oxides of gadolinium, dysprosium, holmium, erbium, and ytterbium, have been reported (90, 91, 195). In addition, those of thulium, lutetium, and a composition approaching that of cerium (III) oxide have also been determined, and five well-characterized compositions between PrOi.714 and PrOi.833 are currently under study (J93). 

The ionic radii for the commonest oxidation states are given in Table 28-1 and are compared with those of the lanthanides in Fig. 28-2. There is clearly an actinide contraction, and the similarities in radii of both series correspond to similarities in their chemical behavior for properties that depend on the ionic radius, such as thermodynamic results for hydrolysis of halides. It is also generally the case that similar compounds in the same oxidation state have similar crystal structures that differ only in the parameters. 

Comparable recent detailed reviews of the actinide halides could not be found. The structures of actinide fluorides, both binary fluorides and combinations of these with main-group elements with emphasis on lattice parameters and coordination poly-hedra, were reviewed by Penneman et al. (1973). The chemical thermodynamics of actinide binary halides, oxide halides, and alkali-metal mixed salts were reviewed by Fuger et al. (1983), and while the preparation of high-purity actinide metals and compounds was discussed by Muller and Spirlet (1985), actinide-halide compounds were hardly mentioned. Raman and absorption spectroscopy of actinide tri- and tetrahalides are discussed in a review by Wilmarth and Peterson (1991). Actinide halides, reviewed by element, are considered in detail in the two volume treatise by Katzet al. (1986). The thermochemical and oxidation-reduction properties of lanthanides and actinides are discussed elsewhere in this volume [in the chapter by Morss (ch. 122)]. 

Grishin, A.E., Kryuchkov, A.S., Butman, M.F. et al. (2007) Suhlimation thermodynamics of some lanthanide tribromide. Proceedings of the 16th International Conference on Chemical Thermodynamics in Russia, Ivanovo, Rnssia, Vol. 1, p. 190. 

The ionic radii of the commonest oxidation states are presented in Table 2. There is evidence of an actinide contraction of ionic radii as the 5/ orbitals are filled and this echoes the well established lanthanide contraction of ionic radii as the 4/orbitals are filled. Actinides and lanthanides in the same oxidation state have similar ionic radii and these similarities in radii are obviously paralleled by similarities in chemical behaviour in those cases where the ionic radius is relevant, such as the thermodynamic properties observed for halide hydrolysis. 

F-Block Element the lanthanides and actinides, valence electrons in the f orbitals Feedstock a process chemical used to produce other chemicals or products Fine Chemicals chemicals produced in relatively low volumes and at higher prices as compared to bulk chemicals such as sulfuric acid, includes flavorings, perfumes, pharmaceuticals, and dyes First Law of Thermodynamics law that states energy in universe is constant, energy cannot be created or destroyed First Order Reaction reaction in which the rate is dependent on the concentration of reactant to the first power... 

Further developments involve the investigation of the mechanism of formation of double- and triple helicates and of the effect of variations in ligand structure on their features, the determination of their physico-chemical (thermodynamic, kinetic, electrochemical, photochemical) properties, the exploration of the coordination chemistry of the ligand strands. For instance, it may be possible to obtain quadruple helical complexes with ions of high coordination number such as the lanthanides and linear ligands containing bipy or terpy units. Using cubic metal ions would also be of interest. 

Crystal field theory is one of several chemical bonding models and one that is applicable solely to the transition metal and lanthanide elements. The theory, which utilizes thermodynamic data obtained from absorption bands in the visible and near-infrared regions of the electromagnetic spectrum, has met with widespread applications and successful interpretations of diverse physical and chemical properties of elements of the first transition series. These elements comprise scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel and copper. The position of the first transition series in the periodic table is shown in fig. 1.1. Transition elements constitute almost forty weight per cent, or eighteen atom per cent, of the Earth (Appendix 1) and occur in most minerals in the Crust, Mantle and Core. As a result, there are many aspects of transition metal geochemistry that are amenable to interpretation by crystal field theory. 

Jones, A.D. and Williams, D.R. (1970) Thermodynamic considerations in co-ordination. Part VIII. A calorimetric and potentiometric study of complex formation between some lanthanide(III) ions and histidine. Journal of the Chemical Society A, 3138-3144. 

Schumm, R. H., Wagman, D. D., Bailey, S., Evans, W. H., and Parker, V. B. Selected values of chemical thermodynamic properties. Tables for the Lanthanide (Rare Earth) elements (Elements 62 through 76 in the Standard Order of Arrangement). Nat l Bur. Stand. Tech. Note 270-7, 75 p. (1973). 

One of the barren regions of chemical thermodynamic values involves fundamental thermal and entropy data for lanthanide compounds despite the fact that these substances provide an unexcelled opportunity for studying the influence of electronic structure on key thermodynamic properties. 

Scandium, yttrium, and the lanthanides represent 17% of all of the elements that can be obtained in coherent form. In view of their similar chemical behavior separation of these elements proved to be formidable (Szabadvary, 1988) but all of the metals have now been obtained in relatively high purity and, except for promethium, their thermodynamic properties have been measured with varying degrees of quality. Based on the interpolation of the properties of neighboring elements, it has also been possible to estimate the thermodynamic properties of promethium in order to complete this review. Because of the radioactive nature of this element and the fact that the most stable isotope has half-life of only 17.7 years, it is unlikely that further measurements will be carried out beyond the very basic properties which have already been determined. 

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