Metalloid

  13 14 15 16 17
2 B
Boron
C
Carbon
N
Nitrogen
O
Oxygen
F
Fluorine
3 Al
Aluminium
Si
Silicon
P
Phosphorus
S
Sulfur
Cl
Chlorine
4 Ga
Gallium
Ge
Germanium
As
Arsenic
Se
Selenium
Br
Bromine
5 In
Indium
Sn
Tin
Sb
Antimony
Te
Tellurium
I
Iodine
6 Tl
Thallium
Pb
Lead
Bi
Bismuth
Po
Polonium
At
Astatine
 
  Commonly recognized (86–99%): B, Si, Ge, As, Sb, Te
  Irregularly recognized (40–49%): Po, At
  Less commonly recognized (24%): Se
  Rarely recognized (8–10%): C, Al
  (All other elements cited in less than 6% of sources)
  Arbitrary metal-nonmetal dividing line: between Be and B, Al and Si, Ge and As, Sb and Te, Po and At

Recognition status, as metalloids, of some elements in the p-block of the periodic table. Percentages are median appearance frequencies in the lists of metalloids.[n 1] The staircase-shaped line is a typical example of the arbitrary metal–nonmetal dividing line found on some periodic tables.

A metalloid is a chemical element which has a preponderance of properties in between, or that are a mixture of, those of metals and nonmetals. The word metalloid comes from the Latin metallum ("metal") and the Greek oeides ("resembling in form or appearance").[1] There is no standard definition of a metalloid and no complete agreement on which elements are metalloids. Despite the lack of specificity, the term remains in use in the literature.

The six commonly recognised metalloids are boron, silicon, germanium, arsenic, antimony and tellurium. Five elements are less frequently so classified: carbon, aluminium, selenium, polonium and astatine. On a standard periodic table, all eleven elements are in a diagonal region of the p-block extending from boron at the upper left to astatine at lower right. Some periodic tables include a dividing line between metals and nonmetals, and the metalloids may be found close to this line.

Typical metalloids have a metallic appearance, may be brittle and are only fair conductors of electricity. They can form alloys with metals, and many of their other physical properties and chemical properties are intermediate between those of metallic and nonmetallic elements. They and their compounds are used in alloys, biological agents, catalysts, flame retardants, glasses, optical storage and optoelectronics, pyrotechnics, semiconductors, and electronics.

The term metalloid originally referred to nonmetals. Its more recent meaning, as a category of elements with intermediate or hybrid properties, became widespread in 1940–1960. Metalloids are sometimes called semimetals, a practice that has been discouraged,[2] as the term semimetal has a more common usage as a specific kind of electronic band structure of a substance. In this context, only arsenic and antimony are semimetals, and commonly recognised as metalloids.


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  1. ^ Oxford English Dictionary 1989, 'metalloid'; Gordh, Gordh & Headrick 2003, p. 753
  2. ^ Cite error: The named reference Atkins2010p20 was invoked but never defined (see the help page).

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