Ionization energy rare earth elements

Table 18.1.2. Ionization energies of rare-earth elements (kJ mol 1)...

The monosulfides of the rare earth elements behave differently from that discussed here since these are metal-like for all but those elements forming the most stable divalent states. Here a general proclivity towards forming tripositive ions seems more important (as in the metals themselves)—a property usually considered to result from a fortuitous balance between ionization and lattice or solvation energies. The sulfides have also been interpreted in terms of a degeneracy of the upper 4f levels with a 5d band (where applicable) (10). In contrast to the halides, there is little differentiation of the electrical properties among the monosulfides, monoselenides, and monotellurides (29). 

Electron energy-loss spectroscopy (EELS), a powerful technique for material characterization at nanometer spatial resolution, has been widely used in chemical microanalysis and the studies of solid-state effects [4]. In EELS, the L ionization edges of transition metal and rare earth elements usually display sharp peaks at the near-edge region, known as white lines. For transition metals with unoccupied 3d states, the transition of an electron from 2p state to 3d levels lead to the formation of white lines. The L3 and L2 lines are the transitions from 2p / to 3d / 3d and from 2p / to 3d /, respectively, and their intensities are related to the unoccupied states in the 3d bands [5,6]. 

The rare earth (RE) ions most commonly used for applications as phosphors, lasers, and amplifiers are the so-called lanthanide ions. Lanthanide ions are formed by ionization of a nnmber of atoms located in periodic table after lanthanum from the cerium atom (atomic number 58), which has an onter electronic configuration 5s 5p 5d 4f 6s, to the ytterbium atom (atomic number 70), with an outer electronic configuration 5s 5p 4f " 6s. These atoms are nsnally incorporated in crystals as divalent or trivalent cations. In trivalent ions 5d, 6s, and some 4f electrons are removed and so (RE) + ions deal with transitions between electronic energy sublevels of the 4f" electroiuc configuration. Divalent lanthanide ions contain one more f electron (for instance, the Eu + ion has the same electronic configuration as the Gd + ion, the next element in the periodic table) but, at variance with trivalent ions, they tand use to show f d interconfigurational optical transitions. This aspect leads to quite different spectroscopic properties between divalent and trivalent ions, and so we will discuss them separately. 

Schick s work includes the study of borides, carbides, nitrides, and oxides of some elements in Groups IIA, IIIB, IVA, IVB, VB, VIIB, and VIII as well as selected rare earths and actinides. As far as possible, the tables have been made compatible with the JANAF tables. Among the subjects treated are phase diagrams, heat capacities, enthalpies, entropies, enthalpies of phase transformation, formation, and reaction, melting temperatures, triple points, free energies of formation, vapour pressures, compositions of vapour species, ionization and appearance potentials, e.m.f. of cells, and enthalpies of solution and dilution. Volume 1 summarizes the techniques used to analyse data and cites the data analysed, and Volume 2 gives tables of values produced by this study. 

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