Metalloids

Metalloids
Name	Metalloids
Caption	Elemental examples and semiconducting devices
Category	Chemical elements
Periodictable group	Various
Properties	Intermediate metallic and nonmetallic characteristics

Metalloids Metalloids occupy a set of elements with intermediate properties between metals and nonmetals, recognized in chemistry, materials science, and engineering. Their classification appears in textbooks, databases, and industrial standards, and they play roles in electronics, metallurgy, and environmental policy. Definitions and boundaries have been debated by researchers, historians, and international organizations across centuries.

Definition and classification

Scientists and organizations such as International Union of Pure and Applied Chemistry, Royal Society of Chemistry, American Chemical Society, National Institute of Standards and Technology, and International Union of Crystallography offer criteria that place elements like boron, silicon, germanium, arsenic, antimony, tellurium, and polonium into the metalloid group. Classification schemes appear in works by Dmitri Mendeleev, Linus Pauling, Glenn T. Seaborg, Alfred Werner, and contributors to the Periodic Table debate, while textbooks from Oxford University Press, Cambridge University Press, and McGraw-Hill present varying lists. Academic journals including Nature, Science, Journal of the American Chemical Society, Angewandte Chemie, and Physical Review Letters publish studies that refine boundary criteria using electronegativity, ionization energy, and band structure, echoed by researchers at Massachusetts Institute of Technology, Stanford University, University of Cambridge, California Institute of Technology, and ETH Zurich.

Physical and chemical properties

Metalloids exhibit intermediate electrical conductivity noted in studies from Bell Labs, IBM Research, Bell Telephone Laboratories, and research groups at Hitachi, Siemens, Intel Corporation, and Samsung Electronics, which exploit semiconducting behavior. Their atomic and crystal structures are characterized by band gaps and covalent bonding discussed in monographs by Linus Pauling, Neal W. Ashcroft, N. David Mermin, and papers in Physical Review B and Proceedings of the National Academy of Sciences. Properties such as semiconductivity, anisotropic conductivity, amphoteric behavior, and variable oxidation states are demonstrated in experimental work by researchers at Lawrence Berkeley National Laboratory, Argonne National Laboratory, Rutherford Appleton Laboratory, and Brookhaven National Laboratory. Thermophysical data, phase diagrams, and alloy behavior feature in compilations by ASM International, CRC Press, Wiley-VCH, and standards from British Standards Institution and International Electrotechnical Commission.

Occurrence and production

Elemental metalloids are found in ores and minerals mined by companies like Rio Tinto, BHP, Glencore, Barrick Gold Corporation, and Vale S.A., and processed at facilities linked to Toshiba, Hitachi Zosen, Kobe Steel, and Outotec. Geological occurrences are documented by institutions such as the United States Geological Survey, Geological Survey of Canada, Geoscience Australia, British Geological Survey, and survey programs like USGS Mineral Resources Program and National Geological Research Institute (Turkey). Extraction and refinement techniques draw on metallurgy research from Kroll Process studies, smelting operations examined at Carnegie Institution for Science, and hydrometallurgical developments reported in conferences hosted by TMS (The Minerals, Metals & Materials Society), ICAME, and Metallurgical Society.

Applications and uses

Metalloids underpin industries and technologies developed by firms and institutions such as Intel Corporation, Texas Instruments, Samsung Electronics, Sony Corporation, Panasonic, Siemens, and GE Aviation. Silicon drives the microelectronics sector represented at events like Consumer Electronics Show and research at MIT Lincoln Laboratory and IBM Research. Germanium and tellurium are critical to photovoltaic and thermoelectric devices advanced by First Solar, SunPower Corporation, Tesla (company), and research teams at National Renewable Energy Laboratory and Fraunhofer Society. Boron compounds and ceramics are used in aerospace and defense applications developed by Boeing, Airbus, Lockheed Martin, and Northrop Grumman, while antimony and arsenic have roles in flame retardants and semiconductors discussed in industry panels at Chemical Industries Association and European Chemical Industry Council.

Health, safety, and environmental impact

Toxicity, exposure limits, and environmental fate of certain metalloids are regulated by agencies such as World Health Organization, Environmental Protection Agency, European Chemicals Agency, Occupational Safety and Health Administration, and Food and Agriculture Organization. Epidemiological and toxicological research published in The Lancet, Environmental Health Perspectives, Toxicological Sciences, and reports by United Nations Environment Programme assess risks from arsenic contamination, antimony leaching, and selenium/tellurium mobility, with remediation projects coordinated by United Nations Development Programme and World Bank. Industrial hygiene practices and safety standards are informed by guidance from National Institute for Occupational Safety and Health, International Labour Organization, Centers for Disease Control and Prevention, and standards bodies like ISO and ASTM International.

Historical background and discovery

Discoveries and characterizations of metalloid elements feature in histories of chemistry authored by Marie Curie, Dmitri Mendeleev, Antoine Lavoisier, John Dalton, and Jöns Jacob Berzelius, and in biographies published by Cambridge University Press and Oxford University Press. Early mineral descriptions appear in accounts by explorers and naturalists associated with institutions such as the British Museum, Smithsonian Institution, Muséum national d'Histoire naturelle, and expeditions sponsored by Royal Society and Académie des Sciences. Industrial-scale production and usage expanded during the Industrial Revolution, influenced by companies like Siemens & Halske, Edison General Electric, General Electric, and later by semiconductor pioneers at Fairchild Semiconductor, Intel Corporation, and research labs at Bell Labs.

Category:Chemical elements