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Metalloids are too brittle to have any structural uses in their pure forms. [105] They and their compounds are used in alloys, biological agents (toxicological, nutritional, and medicinal), catalysts, flame retardants, glasses (oxide and metallic), optical storage media and optoelectronics, pyrotechnics, semiconductors, and electronics. [n 19]
Lists of metalloids differ since there is no rigorous widely accepted definition of metalloid (or its occasional alias, 'semi-metal'). Individual lists share common ground, with variations occurring at the margins. The elements most often regarded as metalloids are boron, silicon, germanium, arsenic, antimony and tellurium.
The chemical elements can be broadly divided into metals, metalloids, and nonmetals according to their shared physical and chemical properties.All elemental metals have a shiny appearance (at least when freshly polished); are good conductors of heat and electricity; form alloys with other metallic elements; and have at least one basic oxide.
Calx – calcium oxide; was also used to refer to other metal oxides. Chalcanthum – the residue produced by strongly roasting blue vitriol (copper sulfate); it is composed mostly of cupric oxide. Chalk – a rock composed of porous biogenic calcium carbonate. CaCO 3; Chrome green – chromic oxide and cobalt oxide.
In 1811, Berzelius referred to nonmetallic elements as metalloids, [17] [18] in reference to their ability to form oxyanions. [19] [20] A common oxyanion of sulfur, for example, is the sulfate ion SO 2− 4. Many metals can do the same. Chromium, for instance, can form the chromate ion CrO 2− 4.
The metallic elements in the periodic table located between the transition metals to their left and the chemically weak nonmetallic metalloids to their right have received many names in the literature, such as post-transition metals, poor metals, other metals, p-block metals, basic metals, and chemically weak metals.
The common oxide of selenium (SeO 3) is strongly acidic. Tellurium. Tellurium is a silvery-white, moderately reactive, [8] shiny solid, that has a density of 6.24 g/cm 3 and is soft (MH 2.25) and brittle. It is the softest of the commonly recognised metalloids.
Another common classification is by degree of metallic or nonmetallic behaviour and characteristics. Elements in the vicinity of where the metals and nonmetals meet are sometime classified as metalloids or an equivalent term. These two to three classes are commonly marked by differing background colors in the periodic table.