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Silicon

Derived from the Latin silex, meaning "flint", silicon is the most common building block of our planet after oxygen. It makes up 26% of the planet's crust and has also been found in meteorites and lunar rocks.

Silicon is always found in chemically and thermally stable mineral combinations but never in its pure form. Silicon is the key to all silicone chemistry as its atomic structure dictates the properties of silicones.

26% of the Earth's crust is made of silicon

26% of the Earth's crust is made of silicon

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Silicon and oxygen have a strong chemical affinity and therefore silicon only occurs naturally in the particularly stable form of Si-O compounds such as calcium, magnesium and iron silicates, as well as SiO2 as sand and quartz. The tetravalent structure is common to all compounds in which silicon is surrounded by oxygen atoms.

 

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Today elemental silicon is obtained through the electro-thermic reduction of SiO2 with carbon at 1,400 degrees Celsius.

Elemental silicon is a dark grey, metallic shiny, hard, and brittle octaedric material. It has a melting point of 1,423°C and a boiling point of 2,630°C. Like carbon, silicon has a crystalline structure similar to that of diamonds.

 

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As a representative of the fourth main group of the periodic table, silicon, like carbon, displays both metallic and non-metallic qualities. There are nevertheless some important differences between the two. The chemical compounds of Si and C are predominantly tetravalent, however both are capable of forming higher or lower coordination numbers. The difference between Si and C lies in the significantly lower electro negativity of Si compared to C (1.8 as opposed to 2.5) and in the larger atomic diameter (1.15 Å as opposed to 0.77 Å). Silicon forms very stable single bonds with the electro negative oxygen while carbon may also form double bonds. Double bonds in silicon chemistry are generally limited to a small number of unstable silane compounds.