Semimetals or Metalloids List

Elements With Properties of Both Metals and Nonmetals

The semimetals or metalloids are found along a zig-zag pattern, starting with boron.
The semimetals or metalloids are found along a zig-zag pattern, starting with boron. ALFRED PASIEKA/SCIENCE PHOTO LIBRARY / Getty Images

This is a list of elements considered to be semimetals or metalloids, elements that have properties of both metals and nonmetals.

Although tennessine is in the last periodic (column) of elements, relativistic effects probably won't make it a noble gas.

Element 117 will most likely be identified as a metalloid, once its properties have been confirmed.

Semimetal or Metalloid Properties

These elements are found in a zig-zag line on the periodic table, separating the basic metals from the nonmetals. However, the defining characteristic of metalloids is not so much their position on the periodic table as the extremely small overlap between the bottom of the conduction band and top of the valence band. A band gap separates a filled valence band from an empty conduction band. Semimetals do not have a band gap.

In general, the metalloids have the physical properties of metals, but they have chemical properties more like nonmetals:

  • Semimetals tend to be used to make excellent semiconductors, although most of the elements themselves are not technically semiconducting. Exceptions are silicon and germanium, which are true semiconductors, as they can conduct electricity under the right conditions.
  • These elements have lower electrical and thermal conductivity than metals.
  • Semimetals/metalloids have high lattice dielectric constants and high diamagnetic susceptibilities.
  • The elements are typically malleable and ductile. An exception is silicon, which is brittle rather than malleable or ductile.
  • Metalloids may either gain or lose electrons in reactions. Oxidation numbers of elements in this group may range from +3 to -2.
  • As far as appearance goes, metalloids may be either dull or shiny and metallic-looking.
  • These elements are extremely important in electronics as semiconductors, although they are also used in optical fibers, added to alloys, added to glass and enamels, and found in some drugs, cleaners, and pesticides. The heavier elements tend to be toxic. Polonium, for example, is dangerous both due to its toxicity and radioactivity.

Distinction Between Semimetals and Metalloids

Some texts use the terms semimetals and metalloids interchangeably, but more recently, the preferred term for the element group is "metalloids," so that "semimetals" may be applied to describe chemical compounds as well as elements that exhibit properties intermediate between metals and nonmetals. An example of a semimetal compound is mercury telluride (HgTe). Some conductive polymers may also be considered semimetals in terms of their behavior.

Other scientists consider arsenic, antimony, bismuth, the alpha allotrope of tin (α-tin), and the graphite allotrope of carbon to be semimetals. This group of elements is called the "classic semimetals."

Other elements also behave like metalloids, so the usual grouping of elements isn't a hard-and-fast rule.

For example, carbon, phosphorus, and selenium exhibit both metallic and nonmetallic character. To some extent, this depends on the form or allotrope of the element. An argument could even be made for calling hydrogen a metalloid, since it normally acts as a nonmetallic gas, but can form a metal.

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Helmenstine, Anne Marie, Ph.D. "Semimetals or Metalloids List." ThoughtCo, Aug. 7, 2017, thoughtco.com/semimetals-or-metalloids-list-606662. Helmenstine, Anne Marie, Ph.D. (2017, August 7). Semimetals or Metalloids List. Retrieved from https://www.thoughtco.com/semimetals-or-metalloids-list-606662 Helmenstine, Anne Marie, Ph.D. "Semimetals or Metalloids List." ThoughtCo. https://www.thoughtco.com/semimetals-or-metalloids-list-606662 (accessed December 15, 2017).