Gold Facts

Chemical & Physical Properties

Periodic Table of the Elements

Gold

Atomic Number: 79

Nugget of native gold from the Washington mining district, California.

Symbol: Au

Atomic Weight: 196.9665

Discovery: known since prehistoric time

Electron Configuration:[Xe]6s¹4f¹⁴5d¹⁰

Word Origin: Sanskrit Jval; Anglo-Saxon gold; meaning gold - also Latin aurum, shining dawn

Isotopes: There are 18 isotopes of gold. Gold-198, with a half-life of 2.7 days, has been used to treat cancer and other illnesses.

Density (g/cc): 19.3

Melting Point (°K): 1337.58

Boiling Point (°K): 3080

Appearance: soft, malleable, yellow metal

Atomic Radius (pm): 146

Atomic Volume (cc/mol): 10.2

Covalent Radius (pm): 134

Ionic Radius: 85 (+3e) 137 (+1e)

Specific Heat (@20°C J/g mol): 0.129

Fusion Heat (kJ/mol): 12.68

Evaporation Heat (kJ/mol): ~340

Debye Temperature (°K): 170.00

Pauling Negativity Number: 2.54

First Ionizing Energy (kJ/mol): 889.3

Oxidation States: 3, 1

Lattice Structure: Face-Centered Cubic (FCC)

Lattice Constant (Å): 4.080

Specific Gravity (20°C): 18.88

Properties: The melting point of gold is an assigned value, which serves as a calibration point for the International Temperature Scale and International Practical Temperature Scale. In mass, gold is a yellow-colored metal, although it may be black, ruby, or purple when finely divided. Gold is the most malleable and ductile metal. One ounce of gold can be beaten out to 300 ft². Gold is a good conductor of electricity and heat. It is not affected by exposure to air or to most reagents. It is inert and a good reflector of infrared radiation. Gold is usually alloyed to increase its strength. Pure gold is measured in troy weight, but when gold is alloyed with other metals the term karat is used to express the amount of gold present.

Uses: Gold is used in coinage and is the standard for many monetary systems. Gold is used for jewelry, dental work, plating, and reflectors. Chlorauric acid (HAuCl₄) is used in photography for toning silver images. Disodium aurothiomalate, administered intramuscularly, is a treatment for arthritis.

Sources: Gold is found as the free metal and in tellurides. It is widely distributed and almost always associated with pyrite or quartz. Gold is found in veins and in alluvial deposits. Gold occurs in sea water in the amount of 0.1 to 2 mg/ton, depending on the location of the sample.