Metallic bonding

A metallic bond or metal bond is defined as the chemical bond, such as is present in the case of metals and alloys. This is characterized by the occurrence of motile ( delocalized ) electrons in the metal lattice, inter alia, for the macroscopic properties of electrical conductivity, metallic luster, ductility ( malleability, ductility ) are responsible. It is caused by electrostatic attractive forces between the metal ions and free electrons.

Formation

The outer electrons ( valence ) of the metals, which are located on the outermost shell are only weakly bound and can therefore be easily separated from the atom. The metal therefore forms a lattice of positively charged metal ions, the so-called atomic cores, each of which carry the core charge. The votes outer electrons are no longer associated with a single atom and can move almost freely within the grid. This is called electron gas or electron gas cloud. Sometimes you designate the electron gas and Fermi gas after the Italian physicist Enrico Fermi. This also means that no firm bond between atomic cores and electrons exists and therefore the bond is non-directional.

Delocalized electrons effect good electrical conductivity and high thermal conductivity of metals, which decreases with increasing temperature. The reason for this lies in the equally increasing lattice vibrations ( phonons), which scatter the charge carriers with increasing temperature more and more. These empirical properties of metals can be derived directly from the band model.

The positively charged atomic cores form a so-called metal mesh (metal crystal ) in which they are arranged similar to the ionic lattice periodic. Here, different lattice types are possible. Frequently occurs in a face-centered cubic lattice with alkali and alkaline earth metals. For transition metals, and the body-centered cubic lattice is stable due to the directed link between the d- orbitals. Other types of gratings are rarely unalloyed metals.

Occurrence

A purely metallic bonding occurs in metallic elements ( metals ) and alloys ( mixtures of metals ) on. Other types of metallic solids have mixed forms of chemical bonds. Some salts, for example, show a transitional form between ionic and metallic bonding, as these metallic shine, but are colored, or current in one direction only good conduct (one-dimensional metals). It is also possible to produce polymers ( polymers that are normally characterized by covalent bond ) with metallic properties. Here delocalized electrons have been " built into" the substance through the targeted insertion of double bonds. At very high pressure, even the normally gaseous material and electrical insulator hydrogen (H2) to accept metallic properties. It is believed that this metallic hydrogen occurs for example in the " gas giant planet " Jupiter and Saturn.

This makes it clear that the terms covalent bond, ionic bond and metallic bond are indeed easier to understand, but for intermediate areas may take the molecular orbital theory better descriptions and predictions.

Intramolecular Interactions: Ionic bond | Covalent bond | Metallic bond | Coordinative binding

Intermolecular interactions: hydrogen bonds | Dipole -dipole interactions | Van der Waals forces

Delocalized π - bond | delocalized σ - bond ( three-center bond, four-center bond)

• Chemical Bonding