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The physical properties of silicon vary considerably in its natural form versus after it has been refined, or as part of a compound structure. It is officially classified as a metalloid, which means it has physical properties of both metal conductors and nonmetal insulators. In its raw form, silicon is found in about a 25% concentration in sand, and is refined for common uses in the manufacture of glass cookware that retains heat well, in ornamental glass products of many varieties, and as an ingredient in concrete. Compounds of silicon have a range of industrial uses due to their durability and ability to withstand high temperatures, making the properties of silicon useful for such products as carbide abrasives, silicate enamels, and silicone gaskets and sealants.
When refined as semiconductor grade silicon (SGS), silicon is at least 99.9999% pure, which makes it a total insulator. SGS is then doped, or implanted, with minute levels of either boron or phosphorus atoms at a level of about one atom of each per one billion atoms of silicon. This changes the properties of silicon from an insulating to semiconducting nature, so that it is useful in the manufacture of microchips.
The chemical properties of silicon include its ability to combine readily with oxygen, and to readily form into either amorphous or crystalline structures at room temperature. Its very high melting point of 2,570° Fahrenheit (1,410° Celsius) makes compounds of the material useful in a wide array of industrial processes. It also alloys readily with metals, such as steel, brass, and aluminum for automotive parts, which makes them stronger and more durable. The mechanical properties of silicon also make it one of the most common elements used in the building trade for everything from caulks to brick and ceramic compounds.
Despite its reputation as a stable element, the properties of silicon in combination with potassium nitrate have been used to make explosives as well. Research as of 2011 has demonstrated its explosive nature as a chemical in combination with gadolinium nitrate, which is equivalent to the explosive yield of ordinary gunpowder. Applications for the discovery may include the development of microchips with sensitive data or structures that can be destroyed by a remote signal when they fall into the wrong hands.
Silicon dioxide, or SiO2, is now known to be the most abundant element in the earth's crust after oxygen, comprising about 28% of the crust's mass. Over 1,000,000 metric tons of silicon were processed into useful forms as of 1999, with nearly half of this production at 400,000 metric tons coming from China. Sources for the material are ordinary sand, quartz, and other crystalline minerals such as amethyst. It is also present in significant quantities in semi-precious stones such as agate, jasper, and opal.
The discovery of silicon and its properties took place between 1789 and 1854 by the work of researchers from many nations, starting with the French chemist known as the Father of Chemistry today, Antoine Lavoisier, first proposing that quartz was an oxide of an unidentified element. Through the 1800s, several chemists isolated samples of silicon, including the English Humphry Davy in 1808, the French chemists Joseph Gay-Lusssac and Louis Thenard in 1811, and the Swedish chemist Jons Berzelius in 1824. The Scottish chemist Thomas Thomson officially named the element silicon in 1831, and, in 1854, the French chemist and minerologist Henri De Ville produced the first relatively pure crystalline silicon. The element was put into commercial production for silicone rubber and greases in 1943, and, by 1958, the first integrated circuit with built-in transistors was manufactured with a silicon substrate.