Gold

This article is about the element. For other uses, see Gold (disambiguation).
"Element 79" redirects here. For the anthology, see Element 79 (anthology).

Gold, 79Au
Gold
AppearanceMetallic yellow
Standard atomic weight Ar°(Au)
Gold in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
Ag
↑
Au
↓
Rg
platinum ← gold → mercury
Atomic number (Z)79
Groupgroup 11
Periodperiod 6
Block  d-block
Electron configuration[Xe] 4f14 5d10 6s1
Electrons per shell2, 8, 18, 32, 18, 1
Physical properties
Phase at STPsolid
Melting point1337.33 K ​(1064.18 °C, ​1947.52 °F)
Boiling point3243 K ​(2970 °C, ​5378 °F)
Density (at 20° C)19.283 g/cm3 [3]
when liquid (at m.p.)17.31 g/cm3
Heat of fusion12.55 kJ/mol
Heat of vaporization342 kJ/mol
Molar heat capacity25.418 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 1646 1814 2021 2281 2620 3078
Atomic properties
Oxidation statescommon: +3
−3,? −2,? −1,[4] 0, +1,[5] +2,[4] +5[4]
ElectronegativityPauling scale: 2.54
Ionization energies
  • 1st: 890.1 kJ/mol
  • 2nd: 1980 kJ/mol
Atomic radiusempirical: 144 pm
Covalent radius136±6 pm
Van der Waals radius166 pm
Color lines in a spectral range
Spectral lines of gold
Other properties
Natural occurrenceprimordial
Crystal structure ​face-centered cubic (fcc) (cF4)
Lattice constant
Face centered cubic crystal structure for gold
a = 407.86 pm (at 20 °C)[3]
Thermal expansion14.13×10−6/K (at 20 °C)[3]
Thermal conductivity318 W/(m⋅K)
Electrical resistivity22.14 nΩ⋅m (at 20 °C)
Magnetic orderingdiamagnetic[6]
Molar magnetic susceptibility−28.0×10−6 cm3/mol (at 296 K)[7]
Tensile strength120 MPa
Young's modulus79 GPa
Shear modulus27 GPa
Bulk modulus180 GPa[8]
Speed of sound thin rod2030 m/s (at r.t.)
Poisson ratio0.4
Mohs hardness2.5
Vickers hardness188–216 MPa
Brinell hardness188–245 MPa
CAS Number7440-57-5
History
Namingfrom Latin aurum 'gold'
DiscoveryIn the Middle East (before 6000 BCE)
Symbol"Au": from Latin aurum
Isotopes of gold
Main isotopes[9] Decay
abun­dance half-life (t1/2) mode pro­duct
195Au synth 186.01 d ε 195Pt
196Au synth 6.165 d β+ 196Pt
β− 196Hg
197Au 100% stable
198Au synth 2.69464 d β− 198Hg
199Au synth 3.139 d β− 199Hg
 Category: Gold
| references

Gold is a chemical element with the chemical symbol Au (from Latin aurum) and atomic number 79. In its pure form, it is a bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal, a group 11 element, and one of the noble metals. It is one of the least reactive chemical elements, being the second-lowest in the reactivity series. It is solid under standard conditions.

Gold often occurs in free elemental (native state), as nuggets or grains, in rocks, veins, and alluvial deposits. It occurs in a solid solution series with the native element silver (as in electrum), naturally alloyed with other metals like copper and palladium, and mineral inclusions such as within pyrite. Less commonly, it occurs in minerals as gold compounds, often with tellurium (gold tellurides).

Gold is resistant to most acids, though it does dissolve in aqua regia (a mixture of nitric acid and hydrochloric acid), forming a soluble tetrachloroaurate anion. Gold is insoluble in nitric acid alone, which dissolves silver and base metals, a property long used to refine gold and confirm the presence of gold in metallic substances, giving rise to the term 'acid test'. Gold dissolves in alkaline solutions of cyanide, which are used in mining and electroplating. Gold also dissolves in mercury, forming amalgam alloys, and as the gold acts simply as a solute, this is not a chemical reaction.

A relatively rare element,[10][11] gold is a precious metal that has been used for coinage, jewelry, and other works of art throughout recorded history. In the past, a gold standard was often implemented as a monetary policy. Gold coins ceased to be minted as a circulating currency in the 1930s, and the world gold standard was abandoned for a fiat currency system after the Nixon shock measures of 1971.

In 2020, the world's largest gold producer was China, followed by Russia and Australia.[12] As of 2020, a total of around 201,296 tonnes of gold exist above ground.[13] This is equal to a cube, with each side measuring roughly 21.7 meters (71 ft). The world's consumption of new gold produced is about 50% in jewelry, 40% in investments, and 10% in industry.[14] Gold's high malleability, ductility, resistance to corrosion and most other chemical reactions, as well as conductivity of electricity have led to its continued use in corrosion-resistant electrical connectors in all types of computerized devices (its chief industrial use). Gold is also used in infrared shielding, the production of colored glass, gold leafing, and tooth restoration. Certain gold salts are still used as anti-inflammatory agents in medicine.

  1. ^ "Standard Atomic Weights: Gold". CIAAW. 2017.
  2. ^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (4 May 2022). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
  3. ^ a b c Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.
  4. ^ a b c Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. ISBN 978-0-08-037941-8.
  5. ^ Mézaille, Nicolas; Avarvari, Narcis; Maigrot, Nicole; Ricard, Louis; Mathey, François; Le Floch, Pascal; Cataldo, Laurent; Berclaz, Théo; Geoffroy, Michel (1999). "Gold(I) and Gold(0) Complexes of Phosphinine‐Based Macrocycles". Angewandte Chemie International Edition. 38 (21): 3194–3197. doi:10.1002/(SICI)1521-3773(19991102)38:21<3194::AID-ANIE3194>3.0.CO;2-O. PMID 10556900.
  6. ^ Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
  7. ^ Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
  8. ^ Kelly, P. F. (2015). Properties of Materials. CRC Press. p. 355. ISBN 978-1-4822-0624-1.
  9. ^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  10. ^ Duckenfield, Mark (2016). The Monetary History of Gold: A Documentary History, 1660–1999. Routledge. p. 4. ISBN 9781315476124. Its scarcity makes it a useful store of value; however, its relative rarity reduced its utility as a currency, especially for transactions in small denominations.
  11. ^ Pearce, Susan M. (1993). Museums, Objects, and Collections: A Cultural Study. Smithsonian Books. p. 53. ISBN 9781588345172. Its scarcity makes it a useful store of value; however, its relative rarity reduced its utility as a currency, especially for transactions in small denominations. ... Rarity is, nevertheless, in itself a source of value, and so is the degree of difficulty which surrounds the winning of the raw material, especially if it is exotic and has to be brought some distance. Gold is, geologically, a relatively rare material on Earth and occurs only in specific places which are remote from most other places.
  12. ^ "Gold Production & Mining Data by Country". 7 June 2023.
  13. ^ "Above-ground stocks". gold.org. Retrieved 18 October 2021.
  14. ^ Soos, Andy (6 January 2011). "Gold Mining Boom Increasing Mercury Pollution Risk". Advanced Media Solutions, Inc. Oilprice.com. Retrieved 26 March 2011.