Silicon (Si)

Metalloids · Period 3 · Solid

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Element identity

Atomic number (Z): 14
Symbol: Si
Atomic weight / isotope mass number: 28.085(1)
Category: Metalloids
Physical state (reference): Solid
Period: 3
Group (reference): 14
Block: p

Physical properties

Appearance: Crystalline, reflective with bluish-tinged faces
Density: 2.3290 g·cm⁻³
Melting point: 1687 K / 1414 °C / 2577 °F
Boiling point: 3538 K / 3265 °C / 5909 °F
Sublimation point: Not available

Atomic and material properties

Electron configuration: [Ne] 3s² 3p²
Electrons per shell: K2 L8 M4
Oxidation states: 4, 3, 2, 1 −1, −2, −3, −4
Electronegativity (Pauling): 1.9
Atomic radius: 111 pm
Covalent radius: 111 pm
Molar ionization energies: 1st: 786.5 kJ·mol⁻¹ 2nd: 1577.1 kJ·mol⁻¹ 3rd: 3231.6 kJ·mol⁻¹ 4th: 4355.5 kJ·mol⁻¹ 5th: 16,091 kJ·mol⁻¹ 6th: 19,805 kJ·mol⁻¹ 7th: 23,780 kJ·mol⁻¹ 8th: 29,287 kJ·mol⁻¹ 9th: 33,878 kJ·mol⁻¹ 10th: 38,726 kJ·mol⁻¹ 11th: 45,962 kJ·mol⁻¹ 12th: 50,502 kJ·mol⁻¹ 13th: 235,196 kJ·mol⁻¹ 14th: 257,923 kJ·mol⁻¹
Thermal conductivity: 149 W·m⁻¹·K⁻¹
Molar heat capacity: 19.789 J·mol⁻¹·K⁻¹
Crystal structure: Diamond cubic
CAS number: 7440-21-3

Property source: Wikipedia — Silicon, adapted from the Nuclides App snapshot. Quoted conditions and qualifiers are retained.

Sources and interpretation

Snapshot exported 24 October 2026 from the element assets used by Nuclides. Properties are a reference compilation, not a new evaluation. Missing values are shown as “Not available”. Density and phase depend on temperature, pressure and allotrope; retained conditions are part of the quoted property.

Atomic weight is dimensionless. Parentheses give uncertainty in the last quoted digits. A single integer in square brackets is an isotope mass number, not a standard atomic weight. The snapshot can differ from current evaluations; consult CIAAW standard atomic weights and the IUPAC periodic table for current values and conventions.

Element properties in the App snapshot are adapted from Wikipedia. Each element page links to its source article; text adaptations are available under CC BY-SA 4.0. No third-party images are included.

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