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Valence (chemistry)

About: Valence (chemistry) is a research topic. Over the lifetime, 24937 publications have been published within this topic receiving 645252 citations. The topic is also known as: valency.


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Journal ArticleDOI
TL;DR: The adsorption of hydrogen on Fe(110, (100) and (111) single crystal planes has been studied by means of low energy diffraction (LEED), thermal desorption spectroscopy (TDS), work function measurements and ultraviolet photoelectron spectroscopic (UPS).

269 citations

Journal ArticleDOI
TL;DR: In this article, a number of copper sulfides and selenides were studied using X-ray photoelectron spectroscopy, and it was found that the copper in all the compounds is monovalent, while the average oxidation state of the chalcogen varies from − 3 2 in Cu3Se2, to − 1 in CuS and CuSe and to built− 1 2 in CoS2 and CoSe2.
Abstract: A number of copper sulphides and selenides were studied using X-ray photoelectron spectroscopy. It was found that the copper in all the compounds is monovalent, while the average oxidation state of the chalcogen varies from —2 in Cu2S and Cu2Se, to − 3 2 in Cu3Se2, to −1 in CuS and CuSe and to built− 1 2 in CuS2 and CuSe2. The deficit of electrons relative to a closed-shell configuration is delocalized (holes in the S(3p) or Se(4p) valence band), leading to p-type metallic conduction. This is also found for the ternary compounds KCu4S3, CuV2S4 and TlCu2Se2. S2− and S− coexist in KCu4S3; the new compounds TlCu4S3 and KCu4Se3 are isostructural with KCu4S3.

267 citations

Journal ArticleDOI
TL;DR: In this article, the effects of a change in the chemical environment of an atom in a surface region are manifested in several subtle ways on the measured Auger electron spectra, such as a shift in the energies of the Auger electrons, which is the result of charge transfer and is a measure of the valence state of the atom.
Abstract: The effects of a change in the chemical environment of an atom in a surface region are manifested in several subtle ways on the measured Auger electron spectra. The first, a shift in the energies of the Auger electrons, is the result of charge transfer and is a measure of the valence state of an atom. Examples of this effect are the oxidation results on refractory metals presented here. It is found that measurable changes are found even for submonolayer coverages of oxygen on an otherwise clean surface. The second main effect is a change in the shape of a complex spectrum, which occurs when some of the electrons involved in this Auger process are valence electrons. The best example of this behavior is that of carbon, and it is found that these complex spectra serve as a fingerprint for the identification of the form of the carbon at a surface. Problems and opportunities for the exploitation of both these effects are discussed, the data included here being illustrative of the usefulness of this type of measurement.

267 citations

Journal ArticleDOI
TL;DR: In this paper, the vibrational spectra of diamond and diamond-like crystals of the elements of Group IV (Si, Ge, and gray Sn) were treated on the basis of a valence force potential.
Abstract: Lattice dynamics and the vibrational spectra of diamond and diamondlike crystals of the elements of Group IV (Si, Ge, and gray Sn) are treated on the basis of a valence force potential. Experimental phonon dispersion curves from the literature are satisfactorily fitted by a six‐parameter valence force potential. The one‐ and two‐phonon absorptions are compared with the calculated density of states g(v) and with the density of combined states J(v). The results are satisfactory. The success in reproducing the spectroscopic properties of all four elements with only these parameters is consistent with the highly directional character of the covalent bonds in the crystal and the lack of ionic character. The different information derived from the widely used shell model and the valence force potential are briefly discussed.

267 citations

Journal ArticleDOI
TL;DR: It is suggested that care must be taken when using quantum chemistry to assess metal-ligand covalency in this part of the periodic table and also topological analysis of the electron density via the quantum theory of atoms-in-molecules.
Abstract: A covalent chemical bond carries the connotation of overlap of atomic orbitals between bonded atoms, leading to a buildup of the electron density in the internuclear region. Stabilization of the valence 5f orbitals as the actinide series is crossed leads, in compounds of the minor actinides americium and curium, to their becoming approximately degenerate with the highest occupied ligand levels and hence to the unusual situation in which the resultant valence molecular orbitals have significant contributions from both actinide and the ligand yet in which there is little atomic orbital overlap. In such cases, the traditional quantum-chemical tools for assessing the covalency, e.g., population analysis and spin densities, predict significant metal–ligand covalency, although whether this orbital mixing is really covalency in the generally accepted chemical view is an interesting question. This review discusses our recent analyses of the bonding in AnCp3 and AnCp4 (An = Th–Cm; Cp = η5-C5H5) using both the trad...

266 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,521
20222,997
2021616
2020611
2019584
2018577