Metallic bond in chemistry examples. Inorganic chemistry

As already indicated in paragraph 4.2.2.1, metal connection- electronic connection of atomic nuclei with minimal localization of shared electrons both on individual (as opposed to ionic bonds) nuclei, and on individual (as opposed to ionic bonds) nuclei covalent bond) connections. As a result, it is an electron-deficient multicenter chemical bond in which shared electrons (in the form of “electron gas”) provide communication with the maximum possible number of nuclei (cations) that form the structure of liquid or solid metallic substances. Therefore, the metallic bond as a whole is non-directional and saturated; it should be considered as limiting case of delocalization of a covalent bond. Let us recall that in pure metals the metallic bond appears primarily homonuclear, i.e. cannot have an ionic component. As a result, a typical picture of the electron density distribution in metals is spherically symmetrical cores (cations) in a uniformly distributed electron gas (Fig. 5.10).

Consequently, the final structure of compounds with a predominantly metallic type of bond is determined primarily by the steric factor and packing density in the crystal lattice of these cations (high CN). The BC method cannot interpret metallic bonds. According to MMO, a metallic bond is characterized by a deficiency of electrons compared to a covalent bond. Strict application of MMO to metallic bonds and connections leads to band theory (electronic model metal), according to which in the atoms included in the crystal lattice of a metal, there is an interaction of almost free valence electrons located in external electron orbits with the (electric) periodic field of the crystal lattice. As a result, the energy levels of electrons split and form a more or less wide band. According to Fermi statistics, the highest energy band is populated by free electrons up to complete filling, especially if the energy terms of an individual atom correspond to two electrons with antiparallel spins. However, it can be partially filled, which provides the opportunity for electrons to move to higher energy levels. Then

this zone is called the conduction zone. There are several main types relative position energy bands corresponding to the insulator, monovalent metal, divalent metal, intrinsic semiconductor, n-type semiconductor and impurity/b-type semiconductor. The ratio of energy bands also determines the type of conductivity of a solid.

However, this theory does not allow us to quantitatively characterize the various metal connections and did not lead to a solution to the problem of the origin of real crystal structures of metal phases. Specifics of nature chemical bond in homonuclear metals, metal alloys and intermetallic heterocompounds is considered by N.V. Ageev)