Metalloid

The semi-metals are elements and are in the periodic table between metals and non-metals. They can of the electrical conductivity and are not attributable to the metals or non-metals in appearance. All metalloids are solids at normal conditions. Semiconductor is an umbrella term and includes semi-metals and compound semiconductor alike.

Older definition

The original definition of the semimetals (or also outdated, metalloids ) is now outdated as something in chemistry. It defines the semi-metals as a series of elements in the III. to VI. Group of the periodic table stand.

To the semi-metals include the following elements:

These elements have both properties of metals and properties of classical non-conductor. They usually occur in two allotropic crystalline forms, one of which is metallic, which carries other non-metallic character. In general, their electrical conductivity is relatively small at room temperature but decreases with increasing temperature to greatly, unlike metals. Therefore, semi-metals are also referred to as elementary semiconductors.

In fact, many of these elements classical semiconductors such as germanium or silicon. Their outer electron shell is filled with three to six electrons, so they can deliver both electrons and absorb.

In the periodic table, the metalloids found in a diagonal between boron and astatine. Elements located right above this line are non-metals; Elements that are left below this line are metals.

Newer definition

In the more recent definition of semi-metals, which is increasingly used in the chemical industry and in particular in the Physics, reference is made longer on the band structure of the solid only on the physical and chemical properties. Semi- metals are then crystalline solids having a band gap, which has the value zero or a value in the range of the thermal energy, with the Boltzmann constant and T is the absolute temperature. A typical representative of the range of the elements are the modification of carbon graphite and gray tin ( α -Sn).

An exact assignment is very difficult, however, because, as mentioned, the different crystal modifications usually have different characteristics. Thus, white tin ( β - tin ), a metal and gray tin ( α -Sn), a semiconductor, but the latter can also be referred to as a semi- metal. The assignment should be organized according to the most common modification at room temperature and normal pressure.

• B, C ( graphite), Si, P (black ), Ge, Se ( gray ), Te according to this classification semiconductor.
• Al, Ga, Sn, Bi, In, Pb, TI metals.

The difficulty of an exact definition of the semimetals shown in the following table: