Together with the metals and nonmetals, the metalloids (in Greek metallon = metal and eidos = sort - also called semimetals) form one of the three categories of chemical elements as classified by ionization and bonding properties. They have properties intermediate between those of metals and nonmetals. There is no unique way of distinguishing a metalloid from a true metal but the most common is that metalloids are usually semiconductors rather than conductors.

The known metalloids (and their atomic symbols) are:

• Boron (B)
• Silicon (Si)
• Germanium (Ge)
• Arsenic (As)
• Antimony (Sb)
• Tellurium (Te)
• Polonium (Po)
• Astatine (At)

In the periodic table, metalloids occur along the diagonal line from boron to polonium. Elements to the upper right of this line are nonmetals; elements to the lower left are metals.

Semi-metallic behaviour is not confined to the elements, but is also found in alloys and compounds. Mercury(II) telluride is one example.

One definition of semi-metallic behavior would be if the conduction band and valence band overlap. This is also true of metals, so semi-metals must additionally have a relatively low carrier density.

Periodic table

Metalloids

شبه فلز | Metaloide | Polumetali | Metal·loide | Polokov | Halbmetall | Poolmetallid | Metaloide | Metaloido | Métalloïde | 준금속 | Polumetali | Metaloid | Málmungur | Metalloidi | מטלואידים | Pusmetaliai | Metalloïde | 半金属 | Halvmetall | Półmetale | Metalóide | Metaloid | Полуметаллы | Metalloid | Polkovina | Металоиди | Metaloid | Puolimetalli | Halvmetall | ธาตุกึ่งโลหะ