metaloids

Metalloids, also called semimetals, are elements whose properties are intermediate between those of metals and nonmetals. They commonly lie along the border between metallic and nonmetallic regions of the periodic table, often forming a diagonal band from boron to polonium. Metalloids tend to be brittle and lustrous, but their electrical conductivity falls between that of metals and nonmetals and can be adjusted by temperature, impurities, or structural changes. Because of this tunable conductivity, they are especially important in electronic applications as semiconductors.

The best-known metalloids are boron, silicon, germanium, arsenic, antimony, tellurium, and polonium; astatine is sometimes considered borderline. Silicon and germanium are foundational semiconductors used in diodes, transistors, and integrated circuits. Boron, arsenic, and antimony are commonly employed as dopants to modify silicon's electrical properties, creating p-type or n-type materials. Tellurium is used in thermoelectric devices and some specialty alloys, while polonium is radioactive and only used in niche laboratory contexts. The set of metalloids is not universally agreed upon, and some elements such as selenium or astatine are variably classified as metalloids depending on the criteria used.

Chemically, metalloids typically exhibit a mix of covalent and ionic bonding tendencies; many form compounds whose acidity or basicity varies with structure. Their electronegativity lies between metals and nonmetals, and their semiconducting behavior is strongly influenced by temperature and by deliberate doping.

In summary, metalloids are a loosely defined group of elements with properties between metals and nonmetals, notable for their role in electronics and materials science. Their exact classification varies with the criteria used.