Silicon · element 14
The stuff of sand, glass and every computer chip, and a quarter of the ground beneath your feet
Key facts
Silicon is the element that makes up most of the rock on Earth and most of the technology in your pocket. Combined with oxygen, it forms the silicate minerals of sand, granite, clay and the vast majority of the crust. Refined to a purity of one foreign atom in a billion, it becomes the crystal wafers on which transistors are printed, and the solar cells that turn sunlight into electricity.
It is a metalloid: a dark grey, glossy, brittle crystal that looks like a metal but conducts electricity poorly, and only when persuaded. That halfway behaviour is exactly what electronics engineers need. A crystal of pure silicon can be tuned by adding tiny amounts of other elements, so that it conducts where and when a circuit designer wants it to.
Where it is found
Silicon is the second most abundant element in the Earth's crust after oxygen, at about 28 per cent by mass. It is almost always bound to oxygen. Quartz is pure silicon dioxide, and it makes up most beach sand. Feldspars, micas, clays, olivine and pyroxenes are all silicates, and they form granite, basalt and the sediments that become sandstone and shale.
Free silicon is not found in nature. Living things make use of silica: diatoms build glass shells from it, grasses and horsetails stiffen their stems with it, and some sponges grow silica skeletons.
How it was discovered
Sand, flint and glass had been worked for thousands of years, and Lavoisier suspected in 1789 that silica contained an unknown element. Humphry Davy tried to extract it by electrolysis and failed, but suggested the name silicium in 1808. In 1817 the Scottish chemist Thomas Thomson proposed silicon instead, arguing that its properties were closer to boron and carbon than to metals.
The Swedish chemist Jons Jacob Berzelius is credited with isolating it in 1824. He heated potassium fluorosilicate with potassium metal, then washed away the by-products to leave a brown powder of amorphous silicon. Its electronic importance came much later: the first silicon transistors were made in 1954, and the integrated circuit followed within a few years.
What we use it for
By volume, silicon's oldest uses are still its largest. Sand and gravel make concrete, and silica sand melted with soda and lime makes glass. Metallurgical grade silicon, around 98 per cent pure, is added to aluminium alloys for castings and to steel. Silicon carbide is an abrasive and a hard ceramic, and increasingly a semiconductor in its own right for the power electronics in electric vehicles.
Electronic grade silicon must be extraordinarily pure. It is grown into single crystals, sliced into wafers and etched with billions of transistors to make the chips in every computer, phone and car. Solar panels are mostly silicon cells. Silicones, which are not the same thing, are rubbery or oily polymers with a backbone of silicon and oxygen atoms, used in sealants, lubricants, bakeware, medical implants and cosmetics.
Reading the numbers
Silicon melts at 1414 degrees Celsius and boils at about 3265 degrees. Its density of 2.33 grams per cubic centimetre is a little more than twice that of water and less than a third of iron's. Unusually, like water, silicon expands when it freezes, so solid silicon floats on the liquid.
The configuration [Ne] 3s2 3p2 gives silicon four outer electrons, exactly like carbon above it in group 14. It bonds covalently to four neighbours in a diamond-like lattice, but the bonds are longer and weaker than carbon's, so electrons can be jostled free by heat or light. That is the origin of its semiconducting behaviour. Its electronegativity of 1.90 places it on the boundary between metals and non-metals. Silicon sits in period 3, and its first four ionisation energies climb steadily before a huge jump to the fifth, marking the neon core.
Safety and the environment
Solid silicon and silica are harmless to touch, but breathing fine crystalline silica dust is not. Long exposure in mining, quarrying, stone cutting and sandblasting causes silicosis, a scarring of the lungs, and raises the risk of lung cancer. Engineered stone worktops have caused a recent rise in cases among the workers who cut them. Silicones and amorphous silica are widely considered safe and appear in food and medicines.
Producing pure silicon is energy intensive, and the chemicals used to etch chips include hazardous gases and acids that must be carefully handled and treated. Against this, silicon solar cells now pay back the energy used to make them within a few years and go on producing clean electricity for decades.
Did you know?
- Silicon makes up about 28 per cent of the Earth's crust by mass, second only to oxygen.
- Like water, silicon expands as it freezes, so solid silicon floats on molten silicon.
- Silicon Valley in California is named after the element because of the semiconductor firms that gathered there.
- Silicone, the rubbery material, is not the element. It is a polymer of silicon and oxygen with carbon groups attached.
- The kilogram was redefined in 2019 with the help of near-perfect spheres of silicon-28, whose atoms could be counted precisely.
- Diatoms, microscopic algae, build intricate glass shells from silica and have done so for over a hundred million years.
More in the metalloids
Column-mates come first, since elements in one column have outer electrons arranged in a similar way and tend to behave alike; the rest are the nearest neighbours in the family.
See all 7 metalloids on one page, or browse all 118 elements.
Compare Silicon with another element
Each comparison has a side-by-side data table and a plain-English summary of the differences.
Frequently asked questions
Is silicon the same as silicone?
No. Silicon is the element, a hard grey crystalline solid used in chips and solar cells. Silicone is a family of soft, flexible polymers made from silicon, oxygen and carbon groups, used in sealants, bakeware and implants. The spelling difference matters.
Why is silicon used in computer chips?
Silicon is a semiconductor, so its conductivity can be switched on and off by adding tiny amounts of other elements and applying small voltages. It also forms a stable insulating oxide on its surface, is abundant and cheap, and can be grown as huge flawless crystals.
Is silicon a metal?
No, it is a metalloid. It has a metallic sheen and forms crystals like a metal, but it is brittle and is a poor conductor of electricity unless deliberately doped. Chemically it behaves more like carbon than like a metal.
Is sand made of silicon?
Most sand is quartz, which is silicon dioxide, so it is roughly half silicon by mass and half oxygen. Some beaches are made of ground-up shells or coral instead, which are calcium carbonate.
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Written by Anthony. Updated September 2026. Numerical data from Periodic-Table-JSON (CC BY-SA), cross-checked against the Silicon reference article. Spotted an error? Tell us.