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METALLOIDS AND SEMICONDUCTORS
by Jonathan Buhalis

Metalloids Nonmetals
Boron
5
Carbon
6
Nitro­gen
7
Oxy­gen
8
O
Fluor­ine
9
F
Alumin­um
13
Sili­con
14
Phos­phorus
15
Sulfur
16
Chlor­ine
17
Cl
Gallium
31
Germa­nium
32
Arsenic
33
Sele­nium
34
Bromine
35
Indium
49
Tin
50
Anti­mony
51
Tellur­ium
52
Iodine
53
Thallium
81
Tl
Lead
82
Bis­muth
83
Polo­nium
84
Po
Asta­tine
85
Metals
Metalloids
Semiconductors

Metalloids

A metalloid is an element that has properties between those of a metal and a nonmetal. Typically, metalloids are lustrous and electrically conductive like a metal, but brittle. Their chemical behavior generally falls between the other two categories.

Metallic elements are on the left side of the periodic table. (The inset is a piece of the table.) Nonmetals are on the right side. The metalloids lie in a diagonal band that runs to the lower right between those two categories. There is no hard rule for exactly which elements are metalloids, but the following are almost always included: boron, silicon, germanium, arsenic, antimony, tellurium, and more doubtfully astatine. Some elements adjacent to these are often included.

Sb, A. Jonathan BuhalisAntimony
As, A. Jonathan BuhalisArsenic
B, A. Jonathan BuhalisBoron
Ge, A. Jonathan BuhalisGermanium
Se, A. Jonathan BuhalisSelenium
Si, A. Jonathan BuhalisSilicon
Te, A. Jonathan BuhalisTellurium

Note that the concept of a metalloid is not quite the same as a semiconductor, but there is considerable overlap. Semiconductors may be elements, but some are compounds.

silicon diodes, A. Jonathan BuhalisSemiconductors
by Jonathan Buhalis

A semiconductor is a material that has electrical conductivity somewhere between a conductor such as most metals and an insulator such as ceramic. Semiconductors have made possible the transistor and other key components of the electronic age.

What makes semiconductors useful is that their electrical conductivity, usually low, can become much higher under certain conditions. Higher temperature increases the conductivity (the opposite behavior of metals). Light can do so as well, hence the solar cell. The diode and the transistor are designed to transmit electrical current one direction but not the other. All of these phenomena let semiconductors act as electronic switches, and that is the basis for computer logic.

The common semiconductors are silicon, germanium, and compounds of gallium and indium.

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Content by Jonathan Buhalis
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