Oxidation states electronic structure

Element Most used isotope Log Half life(year) Source or production Avail amt (g) Electronic structure Oxidation states Origin of name... 

Chemical properties of elements are determined by the valence electronic structure, oxidation states, ionic radii, and coordination number. As already described in OSect. 18.2.1, the oxidation states of the actinide elements are more variable than those of the lanthanides. 

According to the different origins (valence/lat-tice contributions) it is expected that observed quadrupole splittings may reflect information about the electronic structure (oxidation state, spin state), bond properties, and molecular symmetry. As an example the spectra of three iron coordination compounds are shown in Figure 11. 

Several reversible electronic structures (oxidation states) are possible for polyaniline (PAni) ... 

Occluded, possibly neutral, complexes can be prepared by capture in the zeolite cages during synthesis, by post-synthesis sorption from either the gas or liquid phase, or by in situ preparation [17], Such species are submitted to the high electrostatic fields of the zeolite cages (109-11 v.m l) and may interact with nearby acidic sites both factors are likely to alter their electronic structure (oxidation state). Metal carbonyl complexes are probably the most common organometallics which can be used to illustrate this situation [18],... 

Specific form of an element defined according to isotopic composition, electronic or oxidation state, and/or complex or molecular structure... 

According to International Union of Pure and Applied Chemistry (IUPAC), the terms speciation and chemical species should be reserved for the forms of an element defined as to isotopic composition, electronic or oxidation state and/or complex or molecular structure (Templeton el al, 2000). This classical definition, appropriate to speciation in solution samples, would exclude most speciation studies on solid materials, such as soils and sediments, more properly defined as fractionation studies. The terminology used in this chapter is based on the broader definition of speciation given by Ure and Davidson (2002), which encompass the IUPAC s narrow definition and includes the selective extraction and fractionation techniques of solid samples. 

X-ray photoelectron spectroscopy Mossbauer spectroscopy X-ray singlecrystal diffraction XPS (ESCA) Inner-shell electron transitions. Excitation of nuclear spin by y rays. Fourier transform of diffraction data reveals location of electron density. Oxidation state of metal. Oxidation and spin state. Antiferromagnetic coupling (Fe only). Precise three-dimensional structure, bond distances and angles for small molecules. Lower resolution and precision for proteins. 

The application of MOssbauer spectroscopy to silicate mineralogy has been well described in two papers by Bancroft et al, in which the influences of electronic configuration, oxidation state, and coordination symmetry of the iron cations were correlated firstly with silicates of known structures [212], and latterly with silicates of unknown and complex structures [213]. Most of the data discussed here are taken from these works, but references are given where appropriate to other data available. Silicate minerals of lunar origin are discussed on p. 294. 

According to lUPAC recommendations a chemical species is the specific form of an element defined as to isotopic composition, electronic or oxidation state, and/or complex of molecular structure. Speciation analyses are the analytical activities of identifying and/or measuring the quantities of one or more individual chemical species in a sample, while speciation of an element is the distribution of an element amongst defined chemical species in a system. 

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. 

Chromium forms a white solid, hexacarhonyl, Cr(CO)j, with the chromium in formal oxidation state 0 the structure is octahedral, and if each CO molecule donates two electrons, the chromium attains the noble gas structure. Many complexes are known where one or more of the carbon monoxide ligands are replaced by other groups of ions, for example [CrfCOlsI] . 

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