metalloids, or semimetals

Metalloids, or semi-metals, have physical and chemical properties that fall between metals and nonmetals. These include boron, silicon, germanium, arsenic, selenium, antimony, tellurium, and astatine. These brittle elements often have the appearance of metals, but differ greatly in their electrical properties. The electrical conductivities of silicon and germanium lie between those of metals and those of nonmetal insulators. These elements, known as semiconductors, become more conductive at high temperatures, a trait not shared by true metals.