Molecular orbitals electron model

Molecular Orbital Theory Model. Oxygen and hydrogen atoms in H2O are held together by a covalent bond. According to the quantum molecular orbital theory of covalent bonding between atoms, electrons in molecules occupy molecular orbitals that are described, using quantum mechanical language, by a linear combination of... 

This chapter introduces a number of useful graphical models, including molecular orbitals, electron densities, spin densities, electrostatic potentials and local ionization potentials, and relates these models both to molecular size and shape and molecular charge distributions. The chapter also introduces and illustrates property maps which simultaneously depict molecular size and shape in addition to a molecular property. Properties include the electrostatic potential, the value of the LUMO, the local ionization potential and the spin density. 

This chapter introduces and illustrates isosurface displays of molecular orbitals, electron and spin densities, electrostatic potentials and local ionization potentials, as well as maps of the lowest-unoccupied molecular orbital, the electrostatic and local ionization potentials and the spin density (on top of electron density surfaces). Applications of these models to the description of molecular properties and chemical reactivity and selectivity are provided in Chapter 19 of this guide. 

The impact on the electronic structure affecting the oxidation potential and the electron spin distribution has been explained within a simple molecular orbital (MO) model.189 199 As in the bRC the formation of a dimer leads to a decrease of the oxidation potential of the primary donor ( see section 2.1). 

The obvious deficiency of crystal-field theory is that it does not properly take into account the effect of the ligand electrons. To do this a molecular-orbital (MO) model is used in which the individual electron orbitals become a linear combination of the atomic orbitals (LCAO) belonging to the various atoms. Before going into the general problem, it is instructive to consider the simple three-electron example in which a metal atom with one ligand atom whose orbital contains two electrons. Two MO s are formed from the two atomic orbitals... 

A striking analogy exists between localized molecular orbital, electron-domain models of organic and other covalently bonded molecules (Figs. 3—8) and ion-packing models of inorganic compounds 47). 

It would appear that localized molecular orbital, electron-domain models will prove useful in interpretative studies of the structural chemistry of electron-pair donor-acceptor interactions. 

The Hiickel molecular orbital (HMO) model of pi electrons goes back to the early days of quantum mechanics [7], and is a standard tool of the organic chemist for predicting orbital symmetries and degeneracies, chemical reactivity, and rough energetics. It represents the ultimate uncorrelated picture of electrons in that electron-electron repulsion is not explicitly included at all, not even in an average way as in the Hartree Fock self consistent field method. As a result, each electron moves independently in a fully delocalized molecular orbital, subject only to the Pauli Exclusion Principle limitation to one electron of each spin in each molecular orbital. 

Fig. 4.30. Molecular-orbital/band models to illustrate the electronic structures of hematite and ilmenite and based on MS-SCF-Za calculations on FeO , FeOs", and TiO/ clusters. The double arrows labeled (a), (b), (c) refer to electronic transitions giving rise to optical properties (after Vaughan and Tossell, 1978).

A related model that gives a more detailed view of the electron energies and motions is the band model, or the molecular orbital (MO) model, for metals. In this model the electrons are assumed to travel around the metal crystal in MOs formed from the valence atomic orbitals of the metal atoms (Fig. 16.23 on page 784). 

Molecular orbital (MO) model a model that regards a molecule as a collection of nuclei and electrons, where the electrons are assumed to occupy orbitals much as they do in atoms, but having the orbitals extend over the entire molecule. In this model the electrons are assumed to be delocalized rather than always located between a given pair of atoms. (14.2)... 

Models to describe them extend from a simple 4p 4d 5s hybridization scheme, with the inert pair shielding the bonding electrons, up to a molecular orbital-based model of three orthogonal three-center-four-electron bonds. 

The formulation of covalency effects in localized electron systems is conveniently achieved with a molecular orbital (MO) model of bonding, and this approach is widely used to interpret experimental data. Although both com-... 

So it is the second step, made in the KS paper, that has been essential for DFT to become the widely applied method for electronic structure calculations that it is today. We will comment briefly on the historical context of the KS paper. Then a few remarks on practical (computational) aspects of the KS equations will be made and finally the conceptual implications of the KS one-electron or molecular orbital (MO) model and its importance for chemistry now and in the future will be commented on. 

Photoelectron spectroscopy (p.e.s.) has had a remarkable impact on studies of the electronic structure of every kind of molecule since 1968. Its role has been confirmatory with respect to molecular orbital (MO) models and has presented a continuous stimulus for improvements of MO theoretical approaches. 

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