Silicon

METALLOID · GROUP 14 · PERIOD 3
14
Si
Silicon
28.085

Atomic Data

Atomic Number14
SymbolSi
Atomic Weight28.085 u
Density (STP)2.329 g/cm³
Melting Point1413.85 °C (1687 K)
Boiling Point3264.85 °C (3538 K)
Electronegativity1.90 (Pauling)
Electron Config.1s² 2s² 2p&sup6; 3s² 3p²
Oxidation States+4, +2, −4
Phase at STPSolid
CategoryMetalloid
Period / Group3 / 14
CAS Number7440-21-3

Electron Configuration

Si K L M

1s2 2s2 2p6 3s2 3p2

Shell n Subshell Electrons Cumulative
K 1 1s 2 2
L 2 2s 2 4
L 2 2p 6 10
M 3 3s 2 12
M 3 3p 2 14
Total 14 14

Isotopes of Silicon

Silicon has three stable naturally occurring isotopes. Silicon-28 is overwhelmingly dominant at 92.23% natural abundance, making silicon one of the more isotopically uniform elements. No naturally occurring radioactive isotopes exist, though silicon-32 is a trace cosmogenic radioisotope produced by cosmic rays in the atmosphere.

Isotope Symbol Protons Neutrons Abundance Stability
Silicon-28 ²⁸Si 14 14 92.23% Stable
Silicon-29 ²⁹Si 14 15 4.67% Stable
Silicon-30 ³₀Si 14 16 3.10% Stable

Abundance & Occurrence

Silicon is the second most abundant element in Earth's crust at approximately 28% by mass, surpassed only by oxygen. It is never found in pure elemental form in nature — it occurs exclusively in compounds, most commonly as silicon dioxide (SiO₂) in quartz and sand, and as silicate minerals in rocks such as feldspar, mica, and granite. This near-universal presence makes silicon one of the most industrially important elements on the planet.

EARTH'S CRUST COMPOSITION (BY MASS)

Oxygen
46%
Silicon
28%
Aluminum
8%
Iron
5%
Other
13%

GLOBAL SILICON PRODUCTION (BY USE)

Metallurgical
55%
Silicones
25%
Electronics
15%
Other
5%

Discovery & History

Antiquity
Ancient civilisations — Silica (SiO₂) in the form of flint, quartz, and obsidian was used by humans for tools and weapons for hundreds of thousands of years. Glassmaking from silica sand dates to at least 3500 BCE in Mesopotamia and Egypt.
1789
Antoine Lavoisier — Recognised silica (silex) as a probable compound of an unknown element and oxygen, listing it among candidate oxides in his landmark chemical classification, though he could not isolate the element itself.
1808
Humphry Davy — Attempted to isolate silicon using electrolysis but was unsuccessful. He proposed the name silicium for the suspected element, analogous to the Latin silex (flint).
1824
Jöns Jacob Berzelius — First isolated relatively pure amorphous silicon by reducing potassium fluorosilicate (K₂SiF₆) with potassium metal, then washing the product to remove impurities. He is credited as the discoverer and established the modern name silicon.
1954
Gordon Teal (Texas Instruments) — Produced the first practical silicon transistor, displacing germanium as the dominant semiconductor. This milestone launched the Silicon Age of electronics, leading directly to integrated circuits, microprocessors, and the modern digital world.

Safety & Handling

  • Silicosis hazard: Prolonged inhalation of fine crystalline silica dust — generated during quartz cutting, sandblasting, and mining — causes silicosis, an incurable and potentially fatal lung disease. Respiratory protection is mandatory in such environments.
  • Bulk elemental silicon is generally considered non-toxic and is not known to cause harm through skin contact or ingestion under normal conditions.
  • Silicon tetrachloride (SiCl₄): A common processing intermediate that is highly corrosive. It reacts violently with water to release hydrochloric acid fumes and must be handled with chemical-resistant PPE inside a fume hood.
  • Silane gas (SiH₄): Used widely in semiconductor manufacturing; it is pyrophoric, meaning it ignites spontaneously in air, and requires strict gas-handling protocols with appropriate continuous leak detection systems.
  • Silicone polymers and silicon dioxide (glass, sand) are biologically inert and are used safely in food-contact materials, cookware, and medical implants with no known toxicity concerns.
  • Storage: Pure silicon wafers and powders should be stored away from strong oxidisers and fluorine-containing compounds, which react vigorously with silicon even at moderate temperatures.

Real-World Uses

  • Semiconductor chips — Ultra-pure silicon wafers are the substrate for virtually all integrated circuits, microprocessors, and memory chips. Its controllable conductivity, stable oxide layer (SiO₂), and abundance make it the dominant semiconductor material by a wide margin.
  • Solar photovoltaic cells — Crystalline silicon, both monocrystalline and polycrystalline, accounts for over 90% of solar panels worldwide, converting sunlight directly into electricity through the photovoltaic effect.
  • Glass and ceramics — Silicon dioxide (SiO₂) is the primary component of window glass, laboratory glassware, and optical instruments. High-purity fused silica is used for UV-transmitting optics and specialty applications.
  • Optical fibres — High-purity fused silica fibres carry data as pulses of light across intercontinental telecommunications networks with extremely low signal attenuation, forming the backbone of the internet.
  • Silicone polymers — Synthetic polysiloxane materials derived from silicon are used in sealants, lubricants, medical implants, cookware coatings, and personal care products because of their thermal stability and chemical inertness.
  • Concrete and construction — Sand (largely SiO₂) is a primary aggregate in concrete and mortar. Silicon carbide (SiC) serves as an industrial abrasive and high-temperature refractory material.
  • Steel production — Ferrosilicon is added to molten steel as a deoxidiser and alloying agent. Silicon steel, with controlled silicon content, is the standard core material for electrical power transformers due to its low magnetic losses.

Downloadable Resources

Free periodic table reference sheets for classrooms, study sessions, and laboratory use.

Colour PDF Black & White PDF

Frequently Asked Questions

What is silicon used for?

Silicon is used primarily in semiconductor chips that power computers, smartphones, and electronic devices. It is also essential for solar photovoltaic cells, glass and ceramics, silicone polymers, optical fibres, and as a deoxidiser in steel production.

Is silicon the same as silicone?

No. Silicon is a naturally occurring metalloid element (Si), while silicone is a synthetic polymer made from silicon, oxygen, carbon, and hydrogen. Silicones are used in sealants, medical implants, lubricants, and cookware. The two are chemically very different despite having similar names.

Why is silicon used in computer chips?

Silicon is used in computer chips because it is a semiconductor — its electrical conductivity can be precisely controlled by adding small amounts of impurities (doping). It is also abundant, relatively cheap to refine to extreme purity, forms a stable oxide layer (SiO₂) useful for insulation, and can be processed into very thin, large-diameter wafers.

Where is silicon found in nature?

Silicon is the second most abundant element in Earth’s crust at about 28% by mass, but it almost never occurs as a pure element. It is found in quartz (SiO₂), sand, feldspar, mica, and thousands of silicate minerals. The ocean floor and most continental rocks are largely silicate compounds.

Who discovered silicon?

Silicon was first isolated in pure form by Swedish chemist Jöns Jacob Berzelius in 1824. He reduced potassium fluorosilicate with potassium metal to obtain amorphous silicon powder. Earlier, Antoine Lavoisier had identified silica as a compound in 1789, and Humphry Davy attempted but failed to isolate the element in 1808.