- Silicon (Si) is a hard, brittle, crystalline metalloid with atomic number 14, positioned in Group 14 of the periodic table.
- It has four valence electrons in its outermost shell, enabling it to form stable covalent bonds and a vast array of compounds. Its atomic structure consists of fourteen protons, typically fourteen neutrons, and fourteen electrons arranged in three shells (two in the first shell, eight in the second, and four in the third).
- Silicon has three stable isotopes: silicon-28 (²⁸Si), making up about 92.23% of natural silicon; silicon-29 (²⁹Si), about 4.67%; and silicon-30 (³⁰Si), about 3.10%.
- Silicon appears as a dark gray, metallic-looking solid with a diamond cubic crystal structure, and in its pure form it is a semiconductor with properties between metals and nonmetals.
- Silicon is the second most abundant element in Earth’s crust, after oxygen, making up about 27.7% by mass. It is a primary component of most rocks, sand, and soil, predominantly in the form of silicon dioxide (SiO₂) and silicate minerals such as feldspar, mica, and clay. On Earth, silicon is never found in its pure elemental form in nature but occurs bound to oxygen and other elements. Industrially, silicon is produced by reducing quartz (SiO₂) with carbon in an electric arc furnace, yielding metallurgical-grade silicon, which can then be purified further for semiconductor applications.
- The element was first identified in 1787 by Antoine Lavoisier as part of silica, but it was not isolated until 1824, when Swedish chemist Jöns Jacob Berzelius reduced potassium fluorosilicate (K₂SiF₆) with molten potassium, obtaining amorphous silicon. He later refined it to produce crystalline silicon. The name “silicon” derives from the Latin silex or silicis, meaning “flint.”
- Silicon’s most critical industrial role is in electronics, where ultra-pure silicon wafers serve as the foundation for integrated circuits, microchips, and solar cells, forming the backbone of the modern digital world. Its semiconductor properties can be precisely tuned by doping with elements such as phosphorus or boron, enabling control over electrical conductivity. Silicon is also the primary material for photovoltaic cells in solar panels, making it a key player in renewable energy technology.
- Beyond electronics, silicon is essential in the production of glass, ceramics, cement, and silicones (synthetic polymers containing Si–O–Si linkages) used in lubricants, sealants, adhesives, and medical implants. Silicon carbide (SiC) is an extremely hard material used as an abrasive and in high-performance ceramics. Silica gel, a porous form of silicon dioxide, is widely used as a desiccant for moisture control.
- Chemically, silicon is less reactive than carbon but still forms a wide range of compounds, particularly with oxygen. At high temperatures, it reacts with halogens and some metals. In nature, its chemistry is dominated by silicate anions in complex mineral structures. Unlike carbon, silicon rarely forms double bonds and does not readily form stable chains in the same way, which limits its role in biological systems.
- Biologically, silicon is not considered essential for most life forms, but it plays a structural role in certain organisms. Diatoms and some sponges use silica to build protective structures, and trace amounts of silicon may contribute to bone health in humans. Silicon compounds are generally non-toxic, though inhalation of crystalline silica dust can cause silicosis, a serious lung disease.
