Ionic configurations, oxides

It has been shown that different methods may ascribe different bond lengths to the 0-0 and C—O bonds and that the medium and substituents affect the electronic behaviors of carbonyl oxides." For example, recent computational studies (B3LYP/6-31 + G (d, p)) of carbonyl oxides, syn- and awri-methyl carbonyl oxides and dimethylcarbonyl oxides in gas and solution reveal that dipolar character increases with the number of methyl groups, and the ionic configuration is stabilized in a polar medium. These effects result in a weakened 0 0 bond and an increased double-bond character in the CO bond. ... 

In conjunction with these efforts, calculations were made to predict the chemical properties of the Superheavies so that likely ores could be chosen for investigation and separation schemes devised. Separation techniques were developed to purify and identify elements with lifetimes as short as a thousandth of a second. Models were developed to predict such aggregate properties as entropies from samples as small as 500 atoms. Ground-state electron configurations, oxidation states, ionization energies, metallic radii, ionic radii, densities, melting points. 

The problem of the electronic (or ionic) configurations for the three different states of the R elements vapor, metal and oxide, has been described in detail by Gschneidner (1971), Gschneidner and Daane (1988), Gschneidner et al. (1990), and Beaudry and Gschneidner (1978). In the gaseous state two types of configuration are encountered ... 

The nature of the bonding in these monoxides is not fully understood. Bonding in these oxides has been described in terms of the R O ionic configuration with some success. (Ames et al. 1967, Ackermann et al. 1976, Guido and Guigli 1974). But Murad and Hildenbrand (1980) disagree with this model stating that the apparent success of ionic model could be due to a fortuitous adjustment of the... 

This chapter is intended to provide a unified view of selected aspects of the physical, chemical, and biological properties of the actinide elements. The f block elements have many unique features, and a comparison of the lanthanide and actinide transition series provides valuable insights into the properties of both. Comparative data are presented on the electronic configurations, oxidation states, redox potentials, thermochemical data, crystal structures, and ionic radii of the actinide elements, together with a miscellany of topics related to their environmental and health aspects. Much of this material is assembled in tabular and graphical form to facilitate rapid access. Many of the topics covered in this chapter, and some that are not discussed here, are the subjects of subsequent chapters of this work, and these may be consulted for more comprehensive treatments. This chapter provides a welcome opportunity to discuss the biological and environmental aspects of the actinide elements, subjects that were barely mentioned in the first edition of this work but have assumed great importance in recent times. 

Note well the italicized sentence. It implies that the inert pair effect is a relative phenomenon. It emerges only through a comparison with other Groups. For example, the atoms of the Group II elements have configurations of the type [FIS] ns, and in the +2 oxidation state, their ionic configuration is [FIS]. For a Group II element, the process... 

Valence and oxidation state are directly related to the valence-shell electron configuration of a group. Binary hydrides are classified as saline, metallic, or molecular. Oxides of metals tend to be ionic and to form basic solutions in water. Oxides of nonmetals are molecular and many are the anhydrides of acids. 

The number of electrons in the d orbitals depends on the electron configuration of the metal. That configuration can be found from the oxidation state of the metal and its atomic number. As an example, consider [Cr (NH ). The ionic charge on the complex is +3, and because ammonia is a neutral ligand, all the charge... 

Zinc, Cu and Ni have similar ionic radii and electron configurations (Table 5.6). Due to the similarity of the ionic radii of these three metals with Fe and Mg, Zn, Cu and Ni are capable of isomorphous substitution of Fe2+ and Mg2+ in the layer silicates. Due to differences in the electronegativity, however, isomorphous substitution of Cu2+ in silicates may be limited by the greater Pauling electronegativity of Cu2+ (2.0), whereas Zn2+ (1.6) and Ni2+ (1.8) are relatively more readily substituted for Fe2+ (1.8) or Mg2+ (1.3) (McBride, 1981). The three metals also readily coprecipitate with and form solid solutions in iron oxides (Lindsay, 1979 Table 5.7). 

Chromium has a similar electron configuration to Cu, because both have an outer electronic orbit of 4s. Since Cr3+, the most stable form, has a similar ionic radius (0.64 A0) to Mg (0.65 A0), it is possible that Cr3+ could readily substitute for Mg in silicates. Chromium has a lower electronegativity (1.6) than Cu2+ (2.0) and Ni (1.8). It is assumed that when substitution in an ionic crystal is possible, the element having a lower electronegativity will be preferred because of its ability to form a more ionic bond (McBride, 1981). Since chromium has an ionic radius similar to trivalent Fe (0.65°A), it can also substitute for Fe3+ in iron oxides. This may explain the observations (Han and Banin, 1997, 1999 Han et al., 2001a, c) that the native Cr in arid soils is mostly and strongly bound in the clay mineral structure and iron oxides compared to other heavy metals studied. On the other hand, humic acids have a high affinity with Cr (III) similar to Cu (Adriano, 1986). The chromium in most soils probably occurs as Cr (III) (Adriano, 1986). The chromium (III) in soils, especially when bound to... 

I shall take the simple view that most metal oxide structures are derivatives of a closest packed 02 lattice with the metal ions occupying tetrahedral or octahedral holes in a manner which is principally determined by size, charge (and hence stoichiometry) and d configuration (Jj). The presence of d electrons can lead to pronounced crystal field effects or metal-metal bonding. The latter can lead to clustering of metal atoms within the lattice with large distortions from idealized (ionic) geometries. 

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