Chemistry

An Overview about the Chemical Element Silicon



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Silicon

Symbol: Si

Atomic Number: 14

Atomic Mass: 28.0855 amu (atomic mass units)

Melting Point: 1410.0 C (1683.15 K, 2570.0 F)

Boiling Point: 2355.0 C (2628.15 K, 4271.0 F)

Number of Protons/Electrons: 14

Number of Neutrons: 14

Classification: Metalloid

Crystal Structure: Cubic

Density @ 293 K: 2.329 grams per cubic centimeter

Color: grey

Jons Jacob Berzelius, a chemist working in his native, Sweden discovered silicon in 1824. He heated the element potassium in a silica container and then carefully washed the by-products to reveal the amorphous silicon extracted from the silica. A second allotrope, the crystalline form, was made by Henri Etienne Sainte-Claire Deville in 1854. The Latin word for flint is "silicis" and it is from this word that silicon gets its name.

Silicon is the second most abundant element in the earths' crust and the seventh most abundant in the universe. Silicon has not been found as a free element. On Earth it is mainly found in the form of silicon oxide in sand, and minerals such as opal, amethyst, agate and flint. It can also be found as silicates in minerals like feldspar, asbestos and hornblende. It has been detected in the sun and other stars spectroscopically and is found as the principal element in the aerolite class of meteorites.

The element has three naturally occurring elements all of which are stable. The moist common making up 92.230% of the total is silicon-28. In addition eighteen unstable elements are known with half lives ranging from around 200 nanoseconds to 132 years.

The pure element is produced by heating silicon oxide in the form of sand with carbon at a temperature of 2200 C (2473.15 K, 3992 F). Silicon and its compounds have many uses so it is fortunate that it is so common.

* Pure silicon crystals grown using the Czochralski process and doped with other elements such as boron, arsenic or germanium are used in solid state electronics. The applications of such crystals include transistors, microchips and rectifiers.

* Silicon oxide is used to manufacture glass and bricks.

* Silica gel is a colloidal form of silicon oxide that is used as a desiccant.

* Silicon carbide or carborundum is used as an abrasive as it is nearly as hard as diamond.

* Sodium silicate or water-glass is used to produce soaps and adhesives. It is also used as an egg preservative.

* Silicon is a major part of silicone which has many uses. Silicone is used in lubricants, medical implants, electrical insulation and as a polishing agent.

* The compound silicon tetrachloride is used to make smoke screens.

Silicon also has an important biological function. Both fresh water and sea water diatoms extract silica from the water as it forms part of their cell walls.

Production workers in industries where a fine silicon containing dust is produced need to protect their lungs. If such a dust is inhaled it can cause the serious lung disease silicosis.

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