metalloids

Metalloids, also referred to as semimetals, are elements whose properties are intermediate between those of metals and nonmetals. They tend to be brittle, often have a metallic luster, and exhibit electrical conductivity that lies between that of metals and nonmetals. This conductivity can be adjusted by temperature, impurities, or light, making metalloids useful as semiconductors in electronic devices.

Most metalloids occupy a diagonal region on the periodic table that separates metals from nonmetals, commonly described as the stair-step boundary from boron to astatine. The classical list includes boron, silicon, germanium, arsenic, antimony, tellurium, and polonium. Depending on the source, astatine or other elements may be included or excluded, reflecting differences in criteria for classification.

Chemically, metalloids display mixed behavior. They tend to form covalent bonds with nonmetals and can form alloys with metals. Their oxides are often amphoteric or acidic rather than basic, and several metalloids show multiple oxidation states. Silicon and germanium are well known as semiconductors, while boron and arsenic are commonly used as dopants to tailor conductivity in silicon-based electronics.

Metalloids occur across the earth’s crust and play a central role in modern technology. They are essential in electronics, photovoltaics, sensors, and various specialty materials. Due to their intermediate properties, metalloids occupy a nuanced position in chemistry and materials science, with ongoing discussion about the precise boundaries that separate them from neighboring metals and nonmetals.