Covalent bonds electron density

A high electron density surface (also called a bond electron density surface) shows the core of electron density around each atomic nucleus and regions where neighboring atoms share electrons (covalent bonding regions). 

Noteworthy, the distances between Si+ and the coordinating atom of S are merely 5 - 10% longer than covalent bond distances in neutral R3SiX compounds. [117] Accordingly, the silylium ion character of these complexes should be low. This was confirmed by an analysis of the bond electron density, which reveals that covalent Si-S bonds are formed in all complexes. [43] The 29Si NMR shifts are... 

There is no sharp difference between covalent and ion types of bonds. In covalent compounds, electron density is spread almost symmetrically over the partners, its mass centre being in the middle of the distance between atoms, while in purely ionic compounds the maximum of binding electron orbital coincides with the centre of one of the atoms. Polar bonds exhibit asymmetry in the distribution of electron density, mass centre being shifted from the middle to one of the parmers. This shift is characterized by the degree of the bond s ionicity. 

Dunitz, J., and Seiler, P. The absence of bonding electron density in certain covalent bonds as revealed by X-ray analysis. J. Amer. Chem. Soc. 105, 7056 7058 (1983). 

Charge Transfer Charge transfer becomes important where metal-ligand bonds exhibit some degree of covalent character. Electron density from the bound ligands can be transferred to the central metal cation M, and back donation to or from the d-orbitals of transition metals can provide an additional energetic contribution. Charge transfer in SIBFA is based on the expression [53-55]... 

Describe, use, or explain each of the following with respect to forming a covalent bond electron cloud, charge cloud, or charge density valence electrons half-filled electron orbital filled electron orbital electron sharing orbital overlap octet rule or rule of eight. 

Charge density Covalent bond Electron cloud Lewis diagram (formula, structure)... 

Heterogeneous reaction (Section 6 1) A reaction involving two or more substances present in different phases Hydro genation of alkenes is a heterogeneous reaction that takes place on the surface of an insoluble metal catalyst Heterolytic cleavage (Section 4 16) Dissociation of a two electron covalent bond in such a way that both electrons are retained by one of the initially bonded atoms Hexose (Section 25 4) A carbohydrate with six carbon atoms High density lipoprotein (HDL) (Section 26 11) A protein that carries cholesterol from the tissues to the liver where it is metabolized HDL is often called good cholesterol Histones (Section 28 9) Proteins that are associated with DNA in nucleosomes... 

The unequal distribution of electron density in covalent bonds produces a bond dipole, the magnitude of which is expressed by the dipole moment, having the units of charge times distance. Bonds with significant bond dipoles are described as being polar. The bond and group dipole moments of some typical substituents are shown in Table 1.7. 

A common interpretation of the interaction of chalcogens with nucleophiles considers donation of electron density from a lone pair on the donor atom into the o- (E-X) orbital (Figure 15.1). As the degree of covalency increases, a hypervalent three-centre four-electron bond is formed. Real systems fall somewhere between secondary interactions and hypervalent (three centre - four electron) bonds. The two extremes can be distinguished by the correlation of X-E and E D distances.In the hypervalent case both bond distances decrease simultaneously, whereas in the secondary bond the distances are anticorrelated. This concept has been applied in a study of selenoquinones 15.17 (R = Ph, Me) with short Se 0 contacts,for... 

---