Periodic table › Silicon
1. Identity and classification
Hard, brittle crystalline solid with a blue-grey metallic luster
- Name and symbol
- Silicon (Silicon) · Si
- Atomic number
- 14
- Relative atomic weight / mass number
- 28.085 ± 0.001
- Group · period · block
- 14 · 3 · p
- Category
- Metalloid
- State near room temperature
- Solid
- Stable isotopes
- At least one stable isotope
- CAS number
- 7440-21-3
Square brackets [A] indicate a representative isotope mass number, not an average atomic weight. Neutron counts differ between isotopes.
2. Atomic structure and electron configuration
- Protons · electrons in a neutral atom
- 14 · 14
- Neutrons in reference isotope
- 14 (28Si)
- Full electron configuration
1s² 2s² 2p⁶ 3s² 3p²- Abbreviated configuration
[Ne]3s² 3p²- Electrons per shell
- 2, 8, 4
- Listed oxidation states
- +4, +2, -4
- Electronegativity
- 1.9 (Pauling)
- First ionization energy
- 786.548 kJ/mol · 8.152 eV
- Electron affinity
- 133.632 kJ/mol
- Covalent radius
- 111 pm
- van der Waals radius
- 210 pm
Configurations of superheavy elements may include theoretical predictions. Different definitions of atomic radius are not interchangeable.
3. Physical and thermal properties
- Density
- 2.3296 g/cm³
- Melting point
- 1687 K · 1413.85 °C · 2576.93 °F
- Boiling point
- 3538 K · 3264.85 °C · 5908.73 °F
- Crystal structure
- Diamond Cubic
- Specific heat
- 0.705 J/(g·K)
- Thermal conductivity
- 149 W/(m·K)
- Enthalpy of fusion
- 50.21 kJ/mol
- Enthalpy of vaporization
- 359 kJ/mol
- Magnetic ordering
- Diamagnetic
- Mohs hardness
- 6.5
- Speed of sound
- 8433 m/s
Density and structure depend on temperature, pressure and allotrope. 25°C is a room-temperature reference, not STP. Unestablished values are not zero.
4. Chemical behavior and compounds
The listed electron configuration and oxidation states describe atomic structure; compound properties depend on bonding and composition.
Selected compounds: SiO₂ (Silicon dioxide / Quartz) · SiC (Silicon carbide) · Si₃N₄ (Silicon nitride) · SiH₄ (Silane)
Reaction reference
Oxidation behavior depends on temperature, surface passivation and the chemical environment.
Direct reaction with water is element- and condition-dependent.
5. Isotopes
| Isotope | Status | Natural abundance | Half-life |
|---|---|---|---|
| 28Si | Stable | 92.2545% | Stable |
| 29Si | Stable | 4.672% | Stable |
| 30Si | Stable | 3.0735% | Stable |
Half-life units: s seconds, m minutes, h hours, d days, Y years. A dash means no natural-abundance value is given, not zero. Listed records are selected ground states; metastable states are distinct.
6. Discovery and occurrence
- Discovery
- 1854 CE
- Scientists associated with discovery
- Jöns Jacob Berzelius
- Location
- Sweden (Stockholm)
- Origin
- Natural
- Listed crustal abundance
- 282000 ppm
Minerals and naming reference
Quartz (SiO₂), Feldspars, Micas, Olivine, Pyroxenes, Clays (2nd most abundant element in Earth's crust)
From Latin 'silex' or 'silicis' meaning flint or hard stone
7. Applications
Glassware, ceramics, concrete, silicone kitchenware, waterproof sealants, cosmetics
Detailed applications by field
- everyday
- Glassware, ceramics, concrete, silicone kitchenware, waterproof sealants, cosmetics
- industry
- Portland cement, ferrosilicon steel deoxidizer, silicones and lubricants, refractory SiC abrasives
- electronics
- Ultra-pure monocrystalline silicon wafers for microprocessors, RAM, CMOS image sensors, and power MOSFETs
- medicine
- Medical-grade silicone implants, catheters, tubing, and ocular lenses
- energy
- Photovoltaic solar cells (crystalline and amorphous silicon panels)
- aerospace
- High-temperature silicon carbide ceramic matrix composites and thermal protection tiles
- agriculture
- Soluble silicates strengthening cereal crop stems (rice, wheat) against lodging and fungal pests
- science
- Avogadro project ²⁸Si crystal spheres used to redefine the kilogram via Planck's constant
8. Biological role and safety
Hazard depends on the isotope, chemical form, dose and exposure route.
Elemental substances, ions, compounds and radioisotopes can have different health effects. This is an educational reference; laboratory work requires the material safety data sheet and trained supervision.
Biological role reference
Essential for diatoms, radiolarians, andhorsetails to build biogenic silica (opal) frustules; supports collagen and bone mineralization in vertebrates.