Electronic Structure. Bonding

6 Molecular Properties and Spectra 4.1.4.6.1 Electronic Structure. Bonding 

The significant difference between the bond angles in NH3 ( HNH = 106.7°) and NF3 ( FNF = 102.4°) is explained within the valence-shell electron-pair repulsion model of Gillespie (or its earlier variants) by a smaller repulsion of bonding electron pairs in NF3 as compared to 

since in the former, the electrons are drawn towards the more electronegative fluorine atoms [6, 7, 8]. In the valence bond model, the same effect is explained on spatial grounds by a repulsion between nonbonded atoms which is smaller in NF3 than in NH3 [9]. 

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Using MO theory, predict the electronic structure, bond order, and number of unpaired electrons in the peroxide ion, 022-. 

To summarize in contrast to the observed nucleophilic attack of strongly basic nucleophiles on the sulfonyl and sulfoxy sulfur of the three-membered ring sulfones and sulfoxides, the acyclic sulfone and sulfoxide groups are attacked by nucleophiles only with difficulty Although the precise reason for this difference is as yet not clear, it is most probably associated with the geometry, electronic structure, bonding and strain energy of the cyclic compounds. 

A. Simon, Clusters of metals poor in valence electrons - structures, bonding, properties. Angew. Chem. Int. Ed. 27 (1988) 159. 

An extensive system of metallic radii has been formulated on the basis of this equation. It is evident that there is some uncertainty about this empirical equation in particular, the value 0.60 A for the factor of the logarithmic term is somewhat uncertain but, in fact, the conclusions about electronic structure, bond numbers, and valence in metals and intermetallic compounds that have been reached through use of the equation would not be significantly changed by some change in the value of this factor. <... 

The chemistry of transition metal nitrosyls has been reviewed, with spectra of many types used to study the electronic structure. Bonding, as described in Chapter 13, can be thought of as a linear complex of NO, isoelectronic with CO and with NO stretching frequencies of 1700 to 2000 cm or a bent complex of NO , isoelectronic with O2 and with NO stretching frequencies of 1500 to 1700 cm . The number of electrons on the metal ion and the influence of the other ligands on the metal provide for changes from one to the other during reactions. 

The hybrid structure is defined as the superposition of the resonance structures. A benzene ring is often shown with a circle inside a hexagon (in American texts) rather than alternating double bonds — the latter example misrepresents the electronic structure. Bonds with broken w bond orders are often displayed as double bonds with one solid and one dashed line. 

Figure 9.3 The role of ROS in the possible mechanisms by which nanomaterials interact with biological systems. ROS generation is associated with all the four aspects of the mechanisms, in which examples illustrate the importance of material composition, electronic structure, bonded surface species (e.g., metal-containing), surface coatings (active or passive), and solubility, including the contribution of surface species and coatings and interactions with other environmental factors (e.g., UV activation).

Since most of the salient features concerning structure, electronic structure, bonding, and charge transfer are addressed earlier, particularly in section 6.1, emphasis here is placed on some of the more unique and perhaps still controversial results provided by theoretical calculations. Adequate references are, however, provided for the interested reader. 

What are the electronic structures, bond lengths, and bond angles of sulfur dioxide and sulfur trioxide ... 

Ching, W.Y., Ouyang, L, Rulis, P., and Yao, H. (2008) Ah initio study of the physical properties of y-AhOs Lattice dynamics, bulk properties, electronic structure, bonding, optical properties, and ELNES/ XANES spectra. Phys. Rev. E, 78 (1), 014106. 

For the ground-states of other electron-rich molecules, the results of valence-bond calculations from different laboratories - see for example references 24-29 of Chapter 2 - also indicate also indicate that long-bond structures are more important than is usually supposed, and therefore they need to be included in qualitative valence-bond descriptions of their electronic stmcture. This book describes how this can be done, and some of the resulting consequences for the interpretation of the electronic structure, bond properties and reaction mechanisms for various electron-rich molecules. When appropriate, molecular orbital and valence-bond descriptions of bonding are compared, and relationships that exist between them are derived. Considerable attention is given to the use of Pauling 3-electron bonds (A--B as A-B) for providing qualitative valence-bond descriptions of electronic structure. The increased-valence structures for electron-rich molecules - for example... 

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