Physical Properties of Metallic Silicon (Silicon Metal):
Atomic Structure:
Atomic Number: 14
Atomic Weight: 28.085 g/mol
Crystal Structure: Diamond cubic lattice (similar to diamond and germanium).
Appearance and State:
Bluish-gray, brittle crystalline solid with a metallic luster.
Solid at room temperature and standard pressure.
Thermal Properties:
Melting Point: 1,414°C (2,577°F).
Boiling Point: 3,265°C (5,909°F).
Thermal Conductivity: ~149 W/m·K (excellent heat conductor for a semiconductor).
Thermal Expansion Coefficient: 2.6 × 10⁻⁶ K⁻¹ (low expansion reduces thermal stress).
Electrical Properties:
Semiconductor with an electrical resistivity of ~2.3×10³ Ω·m at 20°C.
Conductivity increases with temperature (intrinsic semiconductor behavior).
Mechanical Properties:
Density: 2.33 g/cm³ (2,330 kg/m³).
Mohs Hardness: ~6.5 (comparable to quartz).
Brittleness: Highly brittle; lacks ductility and malleability.
Young's Modulus: 130-188 GPa (stiff material).
Optical Properties:
Reflects infrared light effectively.
Refractive index: ~3.5 (at near-infrared wavelengths).
Magnetic Properties:
Diamagnetic (weakly repelled by magnetic fields).
Isotopes:
Naturally occurring isotopes: ²⁸Si (92.23%), ²⁹Si (4.67%), ³⁰Si (3.10%).
Key Distinctions:
Metallurgical-grade silicon (~98-99% purity) is less refined and more brittle than ultra-high-purity silicon (>99.99%) used in electronics.
Silicon's diamond cubic structure contributes to its brittleness and high melting point.
Applications Driven by Physical Properties:
Thermal Conductivity: Used in heat sinks for electronics.
Semiconductivity: Basis for integrated circuits and solar cells.
Low Thermal Expansion: Ideal for high-temperature environments (e.g., furnace components).
