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.

Physical and Chemical Nature of the Scaling Relations between Adsorption Energies of Atoms on Metal Surfaces

Abstract: Despite their importance in physics and chemistry, the origin and extent of the scaling relations between the energetics of adsorbed species on surfaces remain elusive. We demonstrate here that scalability is not exclusive to adsorbed atoms and their hydrogenated species but rather a general phenomenon between any set of adsorbates bound similarly to the surface. On the example of the near-surface alloys of Pt, we show that scalability is a result of identical variations of adsorption energies with respect to the valence configuration of both the surface components and the adsorbates.

Photocatalysis for Water Decomposition by RuO2-Dispersed ZnGa2O4 with d10 Configuration

Abstract: The photocatalytic activity for water decomposition of RuO2-dispersed ZnGa2O4 with an octahedrally coordinated Ga3+ ion was studied in order to examine the photocatalytic properties of p-block metal oxides with d10 configuration. ZnGa2O4 was impregnated with Ru3(CO)12 or Ru(C5H7O2)3 in THF and oxidized to convert them to RuO2. For RuO2-loaded ZnGa2O4, hydrogen and oxygen were stably produced from the initial stage of reaction under Hg−Xe lamp light irradiation. The activity dependence on the calcination temperature of ZnGa2O4, the amount of RuO2 loaded, and the oxidation temperature of RuO2 showed that the dispersion of small RuO2 particles leads to high photocatalytic activity. The electronic structure of ZnGa2O4 was calculated by a plane-wave-based density function theory (DFT). The valence bands were mainly composed of the O 2p orbitals, whereas the conduction bands were formed by hybridzation of Ga 4s4p and Zn 4s4p orbitals. Large dispersion observed in the conduction band indicated the large mobility...

Modified valence indices from the two-particle density matrix

Abstract: The modified ionic and covalent valence indices are introduced, defined in the framework of the two-particle density matrix, with respect to the reference state of separated atoms or ions (SAL). They include only quadratic contributions in changes of the molecular charge-and-bond order matrix elements, relative to the SAL. General properties of the modified valence indices are examined and illustrative qualitative results for model systems are presented. Numerical UHF SCF MO valence data for selected diatomic and triatomic molecules are reported and interpreted in terms of the valence saturation effect and the ionic vs. covalent valence competition. A three-orbital valence model of a symmetric transition state of the bond-forming–bond-breaking reaction supports the BEBO model postulate of preservation of the total “bond order.” The model predictions are compared with the UHF numerical values. © 1994 John Wiley & Sons, Inc.

The Nature of the Transition Metal–Carbonyl Bond and the Question about the Valence Orbitals of Transition Metals. A Bond Energy Decomposition Analysis of TM(CO)6q (TMq = Hf2–, Ta1–, W0, Re1+, Os2+, Ir3+)

Abstract: The equilibrium geometries and bond-dissociation energies for loss of one CO and loss of six CO from TM(CO)6q (TMq = Hf2-, Ta-, W, Re+, Os2+, Ir3+) have been calculated at the BP86 level using Slat...

Carbon K-shell excitation in small molecules by high-resolution electron impact

Abstract: The excitation of 1s carbon electrons has been observed in CO, CH4, CF4, CO2, COS, C2H2 and C2H4 by means of the electron energy-loss technique with high resolution (70 meV in the 300 eV excitation energy range) and at an incident electron energy of 1.5 keV. The energies, widths and vibrational structures of excited states corresponding to the promotion of 1s carbon electrons to unoccupied valence and Rydberg orbitals have been obtained. The validity of the equivalent-core model, and the role of resonances caused by potential barriers, are discussed.