What Are Metalloids?

Metalloid, also known as semimetal, is a substance between metal and nonmetal. A metalloid is an element that exhibits the characteristics of a metal on the outside, but exhibits both metallic and non-metallic properties in terms of chemical properties. For example, arsenic and antimony, they are hard crystalline solids, apparently metal, but they show two different properties when they are chemically reacted: metal and nonmetal. Some of their oxides are soluble in both acids and bases. This is called amphoteric properties because they behave like both bases and acids. There are many elements that can also form amphoteric compounds. However, this element can only be called a quasi-metal when the duality of this chemical property is very obvious and at the same time it shows the appearance of the metal.

Metalloid is also called "semimetal", "

1. Source and use

Poisonous sand

One of the grades of gloss strength of semi-metallic Iuster. Generally refers to the reflectivity R = 0.19 ~ 0.25, it is slightly darker than the fresh metal polished surface, like the gloss reflected on the surface of old metal utensils, such as the gloss of magnetite. Semi-metallic lustrous minerals are also mostly opaque and rarely used as precious stones.

Metalloids (semimetals) are mostly semiconductors, and their resistivity is between metal and nonmetal. The characteristic of a semi-metallic energy band is that there is a small overlap between its conduction band and its valence band. Without thermal excitation, electrons at the top of the valence band flow into the lower energy conduction band bottom. Therefore, at absolute zero, there is already a certain electron concentration in the conduction band, and there is an equal hole concentration in the valence band. This is the fundamental difference between semimetals and semiconductors. However, due to the small overlap, it is also different from typical metals. This type of material has a small forbidden band width, so it is used to make infrared detection devices. The wavelength of infrared light is about 10 microns, and the corresponding photon energy is 0.1 electron volts. After the semi-metallic material is irradiated with infrared light, the electrons can be rapidly excited from the valence band to the conduction band, causing the conductivity to change, thereby detecting infrared light.

In addition to the above elements, the compound may also be a semi-metal, such as Mg ₂ Pb. Other compounds, such as HgTe, HgSe, and other band gap widths are equal to zero. Sometimes called zero band gap semiconductors, they are also semi-metallic in nature.

The conductivity of these elements varies with temperature and is mostly opposite to that of metals, that is, their conductivity increases with temperature. Metalloids have a wide range of applications and have a wide range of applications in electrical and metallurgical fields, especially in semiconductor materials. ^[3]

From the point of view of the energy band structure, the highest energy band filled by electrons in the metal is half full or partially filled. The electrons can move freely and have a higher electrical conductivity. The highest energy band filled with electrons in an insulator is a full band (also called a valence band), and the forbidden band width between the valence band and the conduction band is large. At room temperature, electrons cannot be excited from the valence band to the conduction band to generate free-moving electrons, so the conductivity is very low. The situation of electronically filled energy bands in semiconductors is similar to that of insulators, but the band gap is smaller. Under a certain doping concentration, conductive free electrons or free holes can be generated. The conductivity of a semiconductor is between the metal and the insulator. In addition, there is an intermediate situation between metals and semiconductors, where the forbidden band width is zero or very small. At this time, the electrons can be excited from the valence band to the conduction band at a very low temperature. Energy exists in both the conduction and valence bands. Free-moving electrons and holes. Like mercury telluride (HgTe), this material is called a semi-metal.