Aug 20 2013
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.