Metalloids: The Semi-Metals

Metalloids, or semi-metals, are a group of elements that possess both properties of metals and non-metals.

The following six elements are commonly regarded as metalloids:

1. Boron
2. Silicon
3. Germanium
4. Arsenic
5. Antimony
6. Tellurium

Properties

Metalloids are brittle, lustrous metallic elements that exhibit semiconductive properties. Unlike metals, they are neither malleable nor ductile. Although they do not readily alloy with metals, each metalloid selectively compounds with certain metal elements to form alloys.

Applications

Being too brittle and weak for structural applications, metalloids are most often used in the chemical, electronics, and alloying industries.

Germanium and silicon were critical in the development of the first transistors in the late 1940s and are, to this day, an integral part of semiconductors and solid-state electronics.

Metallic antimony is widely used in alloys such as pewter and Babbitt, while chemical forms of antimony are used as a flame retardant ingredient in plastics and other materials.

Tellurium is used as an alloying agent to improve the machinability of certain steels, as well as in electro-thermal and photovoltaic applications due to its unique thermal conductivity properties.

Boron, an extremely hard element, is used as a dopant in semiconductors, as a bonding agent in permanent rare earth magnets, as well as in abrasive and chemical substances (e.g. Borax). Used as a dopant in some semiconductors, arsenic is more often found in metal alloys with copper and lead where it acts as a strengthening agent.

Etymology

The terms 'metalloid' comes from the Latin metallum, meaning metal, and oeides, meaning 'resembling in form and appearance'.