Gold (Au) - Properties, Applications

Topics Covered

Introduction
Chemical Properties
Physical Properties
Mechanical Properties
Thermal Properties
Applications

Introduction

Gold is a chemical element with Au as its symbol. It belongs to group 11, periodic number 6 of the periodic table and has the atomic number 79.

Gold is an attractive and highly valued metal that has been in use for thousands of years. It is the one of the most malleable and ductile of all metals known to man. It is a good conductor of heat and electricity. It does not react with oxygen and remains tarnish free, thus leading to its wide usage in jewelry and coinage.

Its resistance to oxidation and harsh chemical environments also makes it useful in industrial applications. Since gold is a very soft metal, it is often alloyed with other metals to increase strength and hardness.

Although gold can be found free in nature, it is usually found along with silver, calcite, tellurium, zinc, quartz, lead, or copper.

Chemical Properties

The chemical properties of gold are provided in the table below.

Chemical Data
CAS number 7440-57-5
Thermal neutron cross section 99 barns/atom
Electrode potential 1.68 V
Ionic radius 0.850 Å
Electronegativity 2.4
X-ray absorption edge 0.15344 Å
Electrochemical equivalent 2.45 g/A/h

Physical Properties

The following table discusses the physical properties of gold.

Properties Metric Imperial
Density 19.32 g/cm3 0.6980 lb/in3
Melting point 1064.43°C 1947.97°F
Boiling point 2000 °C 3632°F

Mechanical Properties

The mechanical properties of gold are tabulated below.

Properties Metric Imperial
Tensile strength 120 MPa 17400 psi
Poisson’s ratio 0.42 0.42
Modulus of elasticity 77.2 GPa 11200 ksi
Shear modulus 27.2 GPa 3950 ksi
Elongation at break 30% 30%
Hardness, Vickers 25 25

Thermal Properties

The thermal properties of gold are tabulated below.

Properties Metric Imperial
Thermal expansion co-efficient (@20-100°C/68-212°F) 14.4 µm/m°C 8 µin/in°F
Thermal conductivity 301 W/mK 2090 BTU in/hr.ft².°F

Applications

About 75% of all gold produced is used in the jewelry industry.

The following are the other application areas of gold:

  • As bullion
  • In electrical connectors and printed circuit boards
  • In labware and electrical contacts
  • In glass
  • Gold-coated mirrors are used to make telescopes that are sensitive to infrared light
  • As gold is a good reflector of infrared radiation, it can be used to help shield spacecraft and skyscrapers from the heat of the sun.

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