They are also used in whiteware ceramics such as porcelain, and in traditional silicate-based soda–lime glass and many other specialty glasses. Silicates are used in Portland cement for mortar and stucco, and mixed with silica sand and gravel to make concrete for walkways, foundations, and roads. Such use includes industrial construction with clays, silica sand, and stone. Most silicon is used commercially without being separated, often with very little processing of the natural minerals. More than 90% of the Earth's crust is composed of silicate minerals, making silicon the second most abundant element in the Earth's crust (about 28% by mass), after oxygen. It is widely distributed in space in cosmic dusts, planetoids, and planets as various forms of silicon dioxide (silica) or silicates. Silicon is the eighth most common element in the universe by mass, but very rarely occurs as the pure element in the Earth's crust. Its melting and boiling points of 1414 ☌ and 3265 ☌, respectively, are the second highest among all the metalloids and nonmetals, being surpassed only by boron. Its oxides form a family of anions known as silicates. It is relatively unreactive.īecause of its high chemical affinity for oxygen, it was not until 1823 that Jöns Jakob Berzelius was first able to prepare it and characterize it in pure form. It is a member of group 14 in the periodic table: carbon is above it and germanium, tin, lead, and flerovium are below it. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. Silicon is a chemical element it has symbol Si and atomic number 14.
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