Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-gray metallic luster, and it is a tetravalent metalloid and semiconductor. It is part of the group 14 on the periodic table, along with carbon above it and germanium, tin, lead, and flerovium below. It is rather unreactive, though less so than its heavier homologues in group 14.
Alloys of silicon are used as deoxidizers in steelmaking and as alloys in aluminum smelting; they are also used in cast iron, particularly for auto engine blocks. Silicon carbide (SiC) is one of the hardest known materials and has been used as an abrasive since ancient times; it is also used as a refractory material owing to its high melting point (3103 K). Silicon dioxide (SiO2), also known as silica, is the major constituent of glass; it forms mixtures with several other oxides that are useful in ceramics and porcelains. Silicates are compounds containing silicon–oxygen covalent bonds; they form about 60% of Earth’s crust by weight but only 1% or less of terrestrial rocks because most have been dissolved by water or converted to other minerals over geological time scales. The largest family of silicate minerals are the feldspars; Feldspar makes up approximately 60% by weight of continental crust besides quartz at 25%.
The abundance of silicon means that this element plays an important role not just in industry but also in everyday life: from food preparation to construction work via computer chips everything we do today relies on silicon’s unique properties!