Hybridization of covalent bonds

An extreme example of hybidization is the structure proposed for sulphur hexafluoride, SF6. The six S-F bonds are directed to the apices of a regular octahedron. An arrangement which would satisfy this number of covalent bonds is sp3d2 hybridization. The ground state of the sulphur atom is s2p4 and 

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Drawing Resonance Hybrids of Covalently Bonded Compounds... 

Organic molecules are generally composed of covalent bonded atoms with several well-defined hybridization states tending to have well-understood preferred geometries. This makes them an ideal case for molecular mechanics parameterization. Likewise, organic molecules are the ideal case for semiempirical parameterization. 

Phosphorus and sulfur are the third-row analogs of nitrogen and oxygen, and the bonding in both can be described using hybrid orbitals. Because of their positions in the third row, however, both phosphorus and sulfur can expand their outer-shell octets and form more than the typical number of covalent bonds. Phosphorus, for instance, often forms five covalent bonds, and sulfur occasionally forms four. 

In summary, the Lewis-like model seems to predict the composition, qualitative molecular shape, and general forms of hybrids and bond functions accurately for a wide variety of main-group derivatives of transition metals. The sd-hybridization and duodectet-rule concepts for d-block elements therefore appear to offer an extended zeroth-order Lewis-like model of covalent bonding that spans main-group and transition-metal chemistry in a satisfactorily unified manner. 

Separation of covalently bonded atoms into QM and MM regions introduces an unsatisfied valence in the QM region this can be satisfied by several different methods. In the frozen-orbital approach a strictly localized hybrid sp2 bond orbital containing a single electron is used at the QM/MM junction [29]. Fro-... 

When the formation of covalent bonds is established between functional groups and a surface, a covalent or chemical functionalization is reached. The main characteristic of this type of functionalization is the change in the carbon hybridization from sp2 to sp3 [104]. Although this covalent functionalization provides the possibility to obtain a... 

Topological analysis of the total density has a considerable advantage over the use of the deformation densities in that it is reference-density independent. There is no need to define hybridized atoms to analyze the nature of covalent bonding, and the ambiguity when using the standard deformation density, noted above in the discussion on propellanes, does not occur. 

The Pu and Am" " ions have a 5 f and 5 f well localized f-shell this is borne out clearly by the fact that their magnetic susceptibility is well explained in the atomic picture (see Chap. D). Nevertheless, this f-configuration is non-localized in metals, therefore, it might well be assumed to form some amount of covalent bonding by hybridization with the 2p electrons of the oxygen ion (see later, and Chap. E). 

Benzene, CgHg, is a common industrial solvent. The benzene molecule is based on a ring of covalently bonded Ccirbon atoms. Draw two acceptable Lewis structures for benzene. Based on the structures, describe a likely resonance hybrid structure for benzene. 

Relative strength of covalent bonds for different combination (hybridization) of bond electrons... 

Hybridization. A satisfactory description of covalent bonding should also be able to account for molecular geometry, that is, for the mutual directions of bonds. Let us take for an example boron trifluoride, which is a trigonal planar molecule. Boron uses three orbitals to form three completely equivalent bonds to fluorine atoms. 

Boron trifluoride and ethylene are but two of the many instances where the directional properties of covalent bonds are better described in terms of overlap of hybrid orbitals than in terms of simple atomic orbitals. 

Shape is crucial, both 7.2 Strengths of Covalent Bonds 7.11 Hybridization and sp3 Hybrid... 

In the absence of hybridization, s-orbital leads to the formation of metallic bond (non-directional) whereas d-orbital leads to the formation of covalent bond (directional). This means the d-orbital of Ti is potentially capable of forming covalent bond with the d-orbital of Ni, providing the energy level of the two d-orbital from Ti and Ni are not too far apart. Now, let us represent this energy level difference as AEd (Ti-Ni). Analogously, there would be AEd (Ti-Co) and AEd (Ti - Fe). From Fig. 5 we see that the order of magnitude for the three AEd s should be... 

Closely associated with hybridization is the whole idea of covalent bonding, the agent which is assumed to link the atoms in a molecule. The exaggerated directional properties assumed for pure and hybrid orbitals alike, feature prominently in the theory of chemical bonding as a function of overlap. Like hybridization, this topic is more than a theory, having become the central dogma of chemistry. 

The quantum content of current theories of chemical cohesion is, in reality, close to nil. The conceptual model of covalent bonding still amounts to one or more pairs of electrons, situated between two atomic nuclei, with paired spins, and confined to the region in which hybrid orbitals of the two atoms overlap. The bond strength depends on the degree of overlap. This model is simply a paraphrase of the 19th century concept of atomic valencies, with the incorporation of the electron-pair conjectures of Lewis and Langmuir. Hybrid orbitals came to be introduced to substitute for spatially oriented elliptic orbits, but in fact, these one-electron orbits are spin-free. The orbitals are next interpreted as if they were atomic wave functions with non-radial nodes at the nuclear position. Both assumptions are misleading. 

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