Lanthanide elements, actinides compared thermodynamic properties

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)]. 

A review of the thermodynamic properties of the actinides and selected comparative data for the lanthanides have been given (Morss 1986). One experimental approach that has been frequently used for obtaining enthalpies of formation of the oxides has been through solution calorimetry, and many data have been acquired for the actinide oxides through Cf in the series. Elements with a higher Z than Cf are not amenable to this technique. 

Gas-phase chemistry studies of atomic and molecular rare-earth and actinide ions have a deep-rooted history of more than three decades. In gas phase, physical and chemical properties of elementary and molecular species can be studied in absence of external perturbations. Due to the relative simplicity of gas-phase systems compared to condensed-phase systems, solutions or solids, it is possible to probe in detail the relationships between electronic structure, reactivity, and energetics. Most of this research involves the use of a variety of mass spectrometry techniques, which allows one exerting precise control over reactants and products. Many new rare earth and actinide molecular and cluster species have been identified that have expanded knowledge of the basic chemistry of these elements and provided clues for understanding condensed-phase processes. Key thermodynamic parameters have been obtained for numerous atomic and molecular ions. Such fundamental physicochemical studies have provided opportunities for the refinement and validation of computational methods as applied to the particularly challenging lanthanide and actinide elements. Among other applications, the roles of... 

The ionic radius is a useful parameter with which to correlate numerous physical and thermodynamic properties of the actinide elemoits. Its usefulness for this purpose is not usually dependent on how it is d ned or on the absolute values that are used when comparing members of the series. Nevertheless, the tom radii implies spherical ions, and the modes of deriving such radii from crystallographic data usually assume that these spheres are in contact with spherical anions. When this assumption is not true, as in most real crystals, the derived radii depend on the method of calculation and are somewhat arbitrary. Consequently, there have been published for the actinide elements several tables of radii which differ both in absolute values and in the slope of the curve obtained when they are plotted against atomic number. All of these sets of radii have in common, however, two qualitative features a contraction of the radius with increasing atomic number and a cusp at the half-filled 5f-electron shell. Additional perturbations of the curve at the one-fourth- and three-fourths-fiUed shells have not been established for the actinides, although slight effects were shown to exist for the lanthanides... 

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