Metalloids

=//**Metalloid:**//=

A **metalloid** is a chemical element with properties that are in-between or a mixture  of those of metals and nonmetals, and which is considered to be difficult to classify unambiguously  as either a metal or a nonmetal. There is no universally agreed or rigorous definition of a metalloid. Classifying any particular element as such has been described as 'arbitrary'[|.] The six elements commonly recognized as metalloids are boron, silicon, germanium, arsenic, antimony and tellurium. They are metallic-looking brittle solids, with intermediate to relatively good electrical conductivities, and each having the electronic band structure of either a semiconductor or a semimetal. Chemically, they mostly behave as (weak) nonmetals, have intermediate ionization energy and electronegativity values, and form amphoteric or weakly acidic oxides. Being too brittle to have any structural uses, the metalloids and their compounds instead find common use in glasses, alloys and semiconductors. The electrical properties of silicon and germanium, in particular, enabled the establishment of the semiconductor industry in the 1950s and the development of solid state electronics from the early 60s onwards. The term //metalloid// was first popularly used to refer to nonmetals. Its more recent meaning as a category of intermediate or hybrid elements did not become widespread until the period 1940–1960. Metalloids are sometimes called semimetals, a practice which has been discouraged. This is because the term semimetal has a different meaning in physics, one which more specifically refers to the electronic band structure of a substance rather than the overall classification of a chemical element.

Elements commonly recognized as metalloids
//This section includes brief sketches of the physical and chemical properties of the applicable elements. For complete profiles, including occurrence, production, history, biological role and precautions, see the main article for each element.// Consistent with the list of metalloid lists, **boron, silicon, germanium, arsenic, antimony** and **tellurium** are commonly classified as metalloids. One or more from among selenium, polonium or astatine are sometimes added to the list. Boron is sometimes excluded from the list, by itself or together with silicon. Tellurium is sometimes not regarded as a metalloid. The inclusion of antimony, polonium and astatine as metalloids has also been questioned.