Metals are all chemical elements in the periodic system on the left and below a dividing line from boron to astatine. Thus, they account for about 80 percent of all chemical elements. The transition to nonmetals through semimetals is seamless and many of them can form modifications with metallic and atomic bonding. The term is also used for alloys and some intermetallic phases. It applies to all materials which have the following four characteristic metallic material properties in solid or liquid form: high electrical conductivity, which decreases with increasing temperature, high thermal conductivity, ductility (deformability) and metallic gloss (mirror finish).