Metallic bonding

Metallic bonding is a type of chemical bonding that arises from the electrostatic attractive force between conduction electrons (in the form of an electron cloud of delocalized electrons) and positively charged metal ions. Metal atoms lose their valence electrons to a large, delocalized orbital, which leaves the nucleus, and other electrons that are closer to the nucleus, as positively charged cations. The ions form a crystal lattice as they are held together by the negative charge of the delocalized orbital. It may be described as the sharing of free electrons among a structure of positively charged ions, and as a more delocalized version of covalent bonding. Metallic bonding accounts for many physical properties of metals, such as strength, ductility, thermal and electrical resistivity and conductivity, opacity, and lustre.

Metallic bonding is not the only type of chemical bonding a metal can exhibit as a pure substance. For example, elemental gallium consists of covalently-bound pairs of atoms in both liquid and solid-state—these pairs form a crystal structure with metallic bonding between them. Another example of a metal–metal covalent bond is the mercurous ion (Hg
₂).