Gold (Au)
Gold is the most chemically inert metal, virtually immune to corrosion in any natural environment. Beyond its traditional roles in jewelry and finance, gold is indispensable in electronics for its unmatched electrical reliability, and increasingly important in medical diagnostics, aerospace, and nanotechnology.
Properties
- Density
- 19,300 kg/m³
- Melting Point
- 1,064 °C
- Boiling Point
- 2,856 °C
- Thermal Conductivity
- 318 W/(m·K)
- Electrical Resistivity
- 2.44 × 10⁻⁸ Ω·m
- Tensile Strength
- 120–220 MPa
- Yield Strength
- 30–205 MPa
- Hardness
- 25–60 HV
- Elongation
- 30–50%
- Crystal Structure
- FCC
Common Grades
- 999.9 (24K): Fine gold, 99.99% pure. Investment bars, electronics, laboratory standards.
- 750 (18K): 75% gold alloy. Premium jewelry, dental crowns, watch cases.
- 585 (14K): 58.5% gold alloy. Popular jewelry standard in many countries.
- Au 99.95%: Industrial-grade gold. Bonding wire, plating solutions, sputtering targets.
Applications
- Electronics: Connector plating, bonding wires, printed circuit boards, semiconductor packaging
- Jewelry: Rings, necklaces, watches, decorative objects, dental prosthetics
- Aerospace: Infrared reflective coatings, electrical connectors in satellites, thermal shielding
- Medical: Diagnostic test strips, drug delivery nanoparticles, dental alloys
- Finance: Central bank reserves, investment bars and coins, exchange-traded funds
FAQ
Why is gold used in electronics rather than silver?
While silver has slightly better conductivity, gold is preferred for connectors because it never tarnishes or corrodes. A gold-plated connector maintains reliable electrical contact for decades without maintenance — critical for aerospace, military, and high-reliability electronics where failure is unacceptable.
How much gold is in a smartphone?
A typical smartphone contains approximately 0.034g of gold, worth about €2–3. The gold is used in connector pins, circuit board traces, and chip wire bonds. While tiny per device, the 1.5 billion smartphones sold annually represent about 50 tonnes of gold.
What is the difference between 18K and 24K gold?
24K is pure gold (99.99%), which is very soft (25 HV) and easily scratched. 18K is 75% gold alloyed with silver, copper, palladium, or zinc to improve hardness and durability. The alloy composition also determines color: yellow (Au-Ag-Cu), white (Au-Pd or Au-Ni), or rose (Au-Cu). Jewelry typically uses 14K–18K for durability.