Gold (Au)
transition-metalSolid
Standard Atomic Weight
196.966569 uElectron configuration
[Xe] 6s1 4f14 5d10Melting point
1064.18 °CBoiling point
2855.85 °CDensity
1.9282e+4 kg/m³Oxidation states
−3, −2, −1, 0, +1, +2, +3, +5Electronegativity (Pauling)
2.54Ionization energy (1st)
9.225554 eVDiscovery year
N/AAtomic radius
135 pmDetails
Gold is a dense, soft transition metal with exceptional resistance to oxidation and corrosion. It is usually found native or alloyed with silver and other precious metals, rather than as common simple ores. Its chemistry is dominated by relativistic effects, which help give the metal its yellow color and influence stable oxidation states. Gold combines high electrical conductivity, malleability, chemical nobility, and cultural value in a way unmatched by most elements.
It is estimated that all the gold in the world, so far refined, could be placed in a single cube 60 ft. on a side. Of all the elements, gold in its pure state is undoubtedly the most beautiful. It is metallic, having a yellow color when in a mass, but when finely divided it may be black, ruby, or purple. The Purple of Cassius is a delicate test for auric gold. It is the most malleable and ductile metal; 1 oz. of gold can be beaten out to 300 ft2. It is a soft metal and is usually alloyed to give it more strength. It is a good conductor of heat and electricity, and is unaffected by air and most reagents.
The name derives from the Sanskrit jval for "shine", the Teutonic word gulth for "shining metal", and the Anglo-Saxon gold of unknown origin. The symbol Au derives from the Latin aurum, for Aurora, the goddess of dawn. Gold was known and highly valued in prehistoric times.
An attractive and highly valued metal, gold has been known for at least 5500 years. Gold is sometimes found free in nature but it is usually found in conjunction with silver, quartz (SiO2), calcite (CaCO3), lead, tellurium, zinc or copper. There is roughly 1 milligram of gold dissolved in every ton of seawater, although extracting it currently costs more than the gold is worth. It has been estimated that all of the gold that has currently been refined could be placed in a cube measuring 20 meters on a side.
Known and highly valued from earliest times, gold is found in nature as the free metal and in tellurides; it is very widely distributed and is almost always associated with quartz or pyrite.
Pure gold is a bright metallic yellow solid at ordinary conditions. It is very malleable and ductile, and freshly exposed surfaces keep their luster in air. Finely divided gold can appear red, purple, or blue because small particles interact with light differently from bulk metal.
Gold is used in jewelry, coinage, bullion, and decorative gilding, often alloyed to improve hardness. In electronics it is valued for corrosion-resistant contacts, bond wires, connectors, and thin coatings. Dentistry has used gold alloys where durability and biocompatibility are important, though use has declined in some settings. Gold nanoparticles are used in diagnostic tests, research reagents, and specialized optical materials. Radioactive ¹⁹⁸Au has had limited medical and tracer applications.
Gold is the most malleable and ductile of all known metals. A single ounce of gold can be beaten into a sheet measuring roughly 5 meters on a side. Thin sheets of gold, known as gold leaf, are primarily used in arts and crafts for gilding. One sheet of gold leaf can be as thin as 0.000127 millimeters, or about 400 times thinner than a human hair.
Pure gold is soft and is usually alloyed with other metals, such as silver, copper, platinum or palladium, to increase its strength. Gold alloys are used to make jewelry, decorative items, dental fillings and coins. The amount of gold in an alloy is measured with a unit called a karat. One karat is equal to one part in twenty-four, so an 18 karat gold ring contains 18 parts pure gold and 6 parts alloy material.
Gold is a good conductor of heat and electricity and does not tarnish when it is exposed to the air, so it can be used to make electrical connectors and printed circuit boards. Gold is also a good reflector of infrared radiation and can be used to help shield spacecraft and skyscrapers from the sun's heat. Gold coated mirrors can be used to make telescopes that are sensitive to infrared light.
A radioactive isotope of gold, gold-198, is used for treating cancer. Gold sodium thiosulfate (AuNa3O6S4) is used as a treatment for arthritis. Chlorauric acid (HAuCl4) is used to preserve photographs by replacing the silver atoms present in an image.
It is used in coinage and is a standard for monetary systems in many countries. It is also extensively used for jewelry, decoration, dental work, and for plating. It is used for coating certain space satellites, as it is a good reflector of infrared and is inert.
Isotopes in Biology
195Au (with a half-life of about 0.51 year) has been used to study particle movement within the lungs of rats [528] G. Patrick, C. Stirling. Environ. Health Perspect.97, 47 (1992).. 198Au (with a half-life of 2.7 days) was used in a study to model gold cycling in plants. This study demonstrated that gold particles are retained by humates (organic constituents of soil), which contain fulvic acid, humic acid, ulmic acid, and lignin and would therefore be likely to accumulate in mull humus or forest litter [529] K. C. Jones, P. J. Peterson. Biogeochemistry7, 3 (1989)..
Isotopes in Medicine
198Au has several medical uses. It has been used as both a diagnostic tool and a treatment option for cancer [530] N. Chanda, P. Kan, L. D. Watkinson, R. Shukla, A. Zambre, T. L. Carmack, H. Engelbrecht, J. R. Lever, K. Katti, G. M. Fent, S. W. Casteel, C. J. Smith, W. H. Miller, S. Jurisson, E. Boote, J. D. Robertson, C. Cutler, M. Dobrovolskaia, R. Kannan, K. V. Katti. Nanomed-Nanotechnol.6, 201 (2010)., [531] C. W. H. Havard, J. McAlister. Br. Med. J.2, 555 (1967)..
–As a diagnostic tool, colloidal 198Au is injected into the affected organ. Normal cells will take up the gold colloid, but tumor cells will not. Therefore, an abscess will show up as a “cold area” on a scan [531] C. W. H. Havard, J. McAlister. Br. Med. J.2, 555 (1967)..
–As a treatment option, gold is intended to provide localized irradiation and can be implanted or injected into the affected area. When implanted, the gold “seed” offers an advantage over other materials in that it can be left in place due to its short half-life (2.7 days). As a colloidal injection, 198Au has been found to produce improvement from a wide variety of cancers [530] N. Chanda, P. Kan, L. D. Watkinson, R. Shukla, A. Zambre, T. L. Carmack, H. Engelbrecht, J. R. Lever, K. Katti, G. M. Fent, S. W. Casteel, C. J. Smith, W. H. Miller, S. Jurisson, E. Boote, J. D. Robertson, C. Cutler, M. Dobrovolskaia, R. Kannan, K. V. Katti. Nanomed-Nanotechnol.6, 201 (2010).. Figure 4.79.1a and 4.79.1b, respectively, show squamous cell carcinoma (cancer) on the lower left eyelid of a cat and the eyelid 6 weeks after implantation of 198Au seeds [532] C. Hardman, R. Stanley. Aust. Vet. J.79, 604 (2001)..
Recent studies have shown the effectiveness of 198Au nanoparticles and nanodevices in reducing tumor size in mice while minimizing radiation spread to other areas [530] N. Chanda, P. Kan, L. D. Watkinson, R. Shukla, A. Zambre, T. L. Carmack, H. Engelbrecht, J. R. Lever, K. Katti, G. M. Fent, S. W. Casteel, C. J. Smith, W. H. Miller, S. Jurisson, E. Boote, J. D. Robertson, C. Cutler, M. Dobrovolskaia, R. Kannan, K. V. Katti. Nanomed-Nanotechnol.6, 201 (2010)., [533] M. K. Khan, L. D. Minc, S. S. Nigavekar, M. S. T. Kariapper, B. M. Nair, M. Schipper, A. C. Cook, W. G. Lesniak, L. P. Balogh. Nanomedicine4, 57 (2008)., [534] H. B. Wheeler, W. E. Jaques, T. W. Botsford. Ann. Surg.141, 208 (1955).. 198Au has been studied and successfully used as an anti-inflammatory (a substance or treatment that reduces the body tissues response to harmful stimuli, such as swelling) for improving arthritic conditions [535] A. M. Spencer, M. P. Patel, B. J. Smits, J. D. F. Williams. Br. Med. J.4 (5937), 153 (1974)., [536] J. R. Topp, E. G. Cross, A. G. Fam. Can. Med. Assoc. J.112, 1085 (1975)..
Gold commonly forms compounds in the +1 and +3 oxidation states, while metallic gold is unusually noble. Chloroauric acid, HAuCl₄, is an important laboratory and refining intermediate, and tetrachloroaurate(III), [AuCl₄]⁻, is a common soluble gold complex. Gold(I) cyanide, AuCN, and dicyanoaurate(I), [Au(CN)₂]⁻, are central to cyanide leaching. Gold forms stable complexes with soft donor ligands such as phosphines, sulfides, and thiolates. Simple gold oxides are relatively unstable compared with those of many transition metals.
See more information at the Gold compound page.
Bulk metallic gold is chemically inert and is generally not a major toxicity hazard, but powders and fumes can present exposure risks in industrial work. Soluble gold salts may be irritants, sensitizers, or systemically toxic, depending on the compound. Cyanide-based gold processing involves hazards from cyanide salts and hydrogen cyanide, HCN, rather than from gold itself. Radioactive gold isotopes require isotope-specific radiation controls.
Gold occurs naturally at very low concentrations in rocks, sediments, seawater, and hydrothermal deposits. Weathering can release native particles that accumulate in placer deposits because of gold's high density and chemical persistence. In soils and waters, gold is usually immobile, but complexation by chloride, cyanide, thiosulfate, or organic sulfur compounds can increase transport. Mining and processing can disturb large volumes of material and may release associated elements such as arsenic or mercury where they are present.
Gold is mined from hard-rock deposits and placers, and is also recovered as a by-product from some copper, nickel, and polymetallic ores. Extraction commonly uses gravity concentration, flotation, smelting, and cyanide leaching, depending on ore type. Supply is supplemented by extensive recycling from jewelry, electronics, and industrial scrap. Demand is split among jewelry, investment, central-bank reserves, and technology. Because gold is highly valued and chemically durable, much of the metal ever refined remains recoverable, although dispersed uses in electronics can be difficult to reclaim economically.
It occurs in veins and alluvial deposits, and is often separated from rocks and other minerals by mining and panning operations. About two thirds of the world's gold output comes from South Africa, and about two thirds of the total U.S. production comes from South Dakota and Nevada. The metal is recovered from its ores by cyaniding, amalgamating, and smelting processes. Refining is also frequently done by electrolysis. Gold occurs in sea water to the extent of 0.1 to 2 mg/ton, depending on the location where the sample is taken. As yet, no method has been found for recovering gold from sea water profitably.
Gold is a rare heavy element in the cosmos. It is produced mainly by rapid neutron-capture nucleosynthesis, with neutron-star mergers strongly implicated and some contribution from rare supernova environments possible. In the early Solar System, gold partitioned strongly into metallic phases, so much of Earth's original inventory is thought to reside in the core. Crustal gold is concentrated by later geological processes.
- Gold can be beaten into leaf thin enough to transmit greenish light.
- The symbol Au comes from the Latin name aurum.
- Gold is one of the few metals that is strongly yellow in bulk form.
- Native gold commonly contains silver; electrum is a natural gold-silver alloy.
- Gold's resistance to tarnish makes it useful for low-current electrical contacts.
- Aqua regia dissolves gold by combining oxidation with chloride complex formation.
Images
Properties
Physical
- Atomic radius (empirical)
- 135 pm Compare Atomic radius (empirical) of all elements →
- Covalent radius
- 136 pm Compare Covalent radius of all elements →
- Van der Waals radius
- 166 pm Compare Van der Waals radius of all elements →
- Metallic radius
- 134 pm Compare Metallic radius of all elements →
- Density
- 1.9282 × 104 kg/m³ Compare Density of all elements →
- Molar volume
- 0.0102 L/mol
- Phase at STP
- Solid Compare Phase at STP of all elements →
- Melting point
- 1064.18 °C Compare Melting point of all elements →
- Boiling point
- 2855.85 °C Compare Boiling point of all elements →
- Thermal conductivity
- 318 W/(m·K) Compare Thermal conductivity of all elements →
- Specific heat capacity
- 0.129 J/(g·K) Compare Specific heat capacity of all elements →
- Molar heat capacity
- 25.418 J/(mol·K) Compare Molar heat capacity of all elements →
- Crystal structure
- Face-centered cubic Compare Crystal structure of all elements →
Chemical
- Electronegativity (Pauling)
- 2.54 Compare Electronegativity (Pauling) of all elements →
- Electronegativity (Allen)
- 1.92
- Electron affinity
- 2.3086 eV
- Ionization energy (1st)
- 9.225554 eV Compare Ionization energy (1st) of all elements →
- Ionization energy (2nd)
- 20.20307 eV Compare Ionization energy (2nd) of all elements →
- Ionization energy (3rd)
- 30.000103 eV Compare Ionization energy (3rd) of all elements →
- Ionization energy (4th)
- 45.000155 eV Compare Ionization energy (4th) of all elements →
- Ionization energy (5th)
- 60.000207 eV Compare Ionization energy (5th) of all elements →
- Oxidation states
- −3, −2, −1, 0, +1, +2, +3, +5 Compare Oxidation states of all elements →
- Valence electrons
- 11 Compare Valence electrons of all elements →
- Electron configuration
- [Xe] 6s1 4f14 5d10
Thermodynamic
- Heat of fusion
- 0.13007203 eV Compare Heat of fusion of all elements →
- Heat of vaporization
- 3.358035 eV Compare Heat of vaporization of all elements →
- Heat of sublimation
- 3.814064 eV
- Heat of atomization
- 3.814064 eV
- Atomization enthalpy
- 3.816137 eV
Nuclear
- Protons
- 79 Compare Protons of all elements →
- Neutrons
- 118 Compare Neutrons of all elements →
- Known isotopes
- 43 Compare Known isotopes of all elements →
- Stable isotopes
- 1 Compare Stable isotopes of all elements →
- Most stable isotope
- Au-197
Abundance
- Abundance (Earth's crust)
- 0.004 mg/kg Compare Abundance (Earth's crust) of all elements →
- Abundance (ocean)
- 4 × 10−6 mg/L Compare Abundance (ocean) of all elements →
Crystal Structure
- Lattice constant a
- 408 pm
Electronic Structure
- Electrons per shell
- 2, 8, 18, 32, 18, 1 Compare Electrons per shell of all elements →
Identifiers
- CAS number
- 7440-57-5 Compare CAS number of all elements →
- Term symbol
- 2S1/2
- InChI
- InChI=1S/Au
- InChI Key
- PCHJSUWPFVWCPO-UHFFFAOYSA-N
Electron Configuration Measured
Au: 4f¹⁴ 5d¹⁰ 6s¹[Xe] 4f¹⁴ 5d¹⁰ 6s¹1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s¹Atomic model
Isotopes change neutron count, mass, and stability — not the electron configuration of a neutral atom.
Schematic atomic model, not to scale.
Atomic Fingerprint
Emission / Absorption Spectrum
Isotope Distribution
| Mass number | Atomic mass (u) | Natural abundance | Half-life |
|---|---|---|---|
| 197 Stable | 196.96656879 ± 0.00000071 | 100.0000% | Stable |
Phase / State
Reason: 1039.2 °C below melting point (1064.18 °C)
Schematic, not to scale
Phase transition points
Transition energies
Energy required to melt 1 mol at melting point
Energy required to vaporize 1 mol at boiling point
Energy required to sublime 1 mol at sublimation point
Density
At standard conditions
At standard conditions
Atomic Spectra
Showing 10 of 79. Sorted by ion charge (ascending).
Lines Holdings ?
| Ion | Charge | Total lines | Transition probabilities | Level designations |
|---|---|---|---|---|
| Au I | 0 | 191 | 20 | 90 |
| Au II | +1 | 111 | 0 | 10 |
| Au III | +2 | 150 | 0 | 0 |
Levels Holdings ?
| Ion | Charge | Levels |
|---|---|---|
| Au I | 0 | 75 |
| Au II | +1 | 48 |
| Au III | +2 | 2 |
| Au IV | +3 | 2 |
| Au V | +4 | 2 |
| Au VI | +5 | 2 |
| Au VII | +6 | 2 |
| Au VIII | +7 | 2 |
| Au IX | +8 | 2 |
| Au X | +9 | 2 |
Ionic Radii
| Charge | Coordination | Spin | Radius |
|---|---|---|---|
| +1 | 6 | N/A | 137 pm |
| +3 | 4 | N/A | 68 pm |
| +3 | 6 | N/A | 85 pm |
| +5 | 6 | N/A | 56.99999999999999 pm |
Compounds
Isotopes (1)
The most common gold compounds are auric chloride and chlorauric acid, the latter being used in photography for toning the silver image. Gold has 18 isotopes; 198Au, with a half-life of 2.7 days, is used for treating cancer and other diseases. Disodium aurothiomalate is administered intramuscularly as a treatment for arthritis. A mixture of one part nitric acid with three of hydrochloric acid is called aqua regia (because it dissolved gold, the King of Metals). Gold is available commercially with a purity of 99.999+%. For many years the temperature assigned to the freezing point of gold has been 1063.0C; this has served as a calibration point for the International Temperature Scales (ITS-27 and ITS-48) and the International Practical Temperature Scale (IPTS-48). In 1968, a new International Practical Temperature Scale (IPTS-68) was adopted, which demands that the freezing point of gold be changed to 1064.43C. The specific gravity of gold has been found to vary considerably depending on temperature, how the metal is precipitated, and cold-worked.
| Mass number | Atomic mass (u) | Natural abundance | Half-life | Decay mode | |
|---|---|---|---|---|---|
| 197 Stable | 196.96656879 ± 0.00000071 | 100.0000% | Stable | stable |
Extended Properties
Covalent Radii (Extended)
- Covalent radius (Pyykkö)
- 124 pm
- Covalent radius (Pyykkö, double)
- 121 pm
- Covalent radius (Pyykkö, triple)
- 123 pm
Van der Waals Radii
- Batsanov
- 210 pm
- Alvarez
- 232 pm
- UFF
- 329.3 pm
- MM3
- 243 pm
Atomic & Metallic Radii
- Atomic radius (Rahm)
- 226 pm
- Metallic radius (C12)
- 144 pm
Numbering Scales
- Mendeleev
- 73
- Pettifor
- 70
- Glawe
- 66
Electronegativity Scales
- Ghosh
- 0
- Miedema
- 5
- Gunnarsson–Lundqvist
- 5
- Robles–Bartolotti
- 4
Polarizability & Dispersion
- Dipole polarizability
- 36 a.u.
- Dipole polarizability (unc.)
- 3 a.u.
- C₆ (Gould–Bučko)
- 427 Ha·Bohr6
Miedema Parameters
- Miedema molar volume
- 10.2 cm3/mol
- Miedema electron density
- 4
Supply Risk & Economics
- Production concentration
- 13
- Relative supply risk
- 6
- Reserve distribution
- 15
- Political stability (top producer)
- 24
- Political stability (top reserve)
- 75
Phase Transitions & Allotropes
| Melting point | 1337.33 K |
| Boiling point | 3109.15 K |
Oxidation State Categories
Advanced Reference Data
Screening Constants (14)
| n | Orbital | σ |
|---|---|---|
| 1 | s | 1.5239 |
| 2 | p | 4.4868 |
| 2 | s | 20.6302 |
| 3 | d | 13.4917 |
| 3 | p | 22.297 |
| 3 | s | 23.2372 |
| 4 | d | 37.472 |
| 4 | f | 38.3504 |
| 4 | p | 35.4532 |
| 4 | s | 34.5868 |
Crystal Radii Detail (4)
| Charge | CN | Spin | rcrystal (pm) | Origin |
|---|---|---|---|---|
| 1 | VI | 151 | Ahrens (1952) ionic radius, | |
| 3 | IVSQ | 82 | ||
| 3 | VI | 99 | Ahrens (1952) ionic radius, | |
| 5 | VI | 71 |
Isotope Decay Modes (71)
| Isotope | Mode | Intensity |
|---|---|---|
| 168 | p | — |
| 169 | p | — |
| 169 | A | — |
| 169 | B+ | — |
| 170 | p | 89% |
| 170 | A | 11% |
| 171 | p | 100% |
| 171 | A | — |
| 172 | A | 100% |
| 172 | p | — |
X‑ray Scattering Factors (506)
| Energy (eV) | f₁ | f₂ |
|---|---|---|
| 10 | — | 1.73645 |
| 10.1617 | — | 1.81425 |
| 10.3261 | — | 1.89553 |
| 10.4931 | — | 1.98045 |
| 10.6628 | — | 2.06919 |
| 10.8353 | — | 2.16029 |
| 11.0106 | — | 2.25522 |
| 11.1886 | — | 2.35433 |
| 11.3696 | — | 2.45698 |
| 11.5535 | — | 2.56237 |
Additional Data
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
4×10-3 milligrams per kilogram
References (1)
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
4×10-6 milligrams per liter
References (1)
Sources
Sources of this element.
It occurs in veins and alluvial deposits, and is often separated from rocks and other minerals by mining and panning operations. About two thirds of the world's gold output comes from South Africa, and about two thirds of the total U.S. production comes from South Dakota and Nevada. The metal is recovered from its ores by cyaniding, amalgamating, and smelting processes. Refining is also frequently done by electrolysis. Gold occurs in sea water to the extent of 0.1 to 2 mg/ton, depending on the location where the sample is taken. As yet, no method has been found for recovering gold from sea water profitably.
References (1)
- [6] Gold https://periodic.lanl.gov/79.shtml
References
(9)
Data deposited in or computed by PubChem
The half-life and atomic mass data was provided by the Atomic Mass Data Center at the International Atomic Energy Agency.
Element data are cited from the Atomic weights of the elements (an IUPAC Technical Report). The IUPAC periodic table of elements can be found at https://iupac.org/what-we-do/periodic-table-of-elements/. Additional information can be found within IUPAC publication doi:10.1515/pac-2015-0703 Copyright © 2020 International Union of Pure and Applied Chemistry.
The information are cited from Pure Appl. Chem. 2018; 90(12): 1833-2092, https://doi.org/10.1515/pac-2015-0703.
Thomas Jefferson National Accelerator Facility (Jefferson Lab) is one of 17 national laboratories funded by the U.S. Department of Energy. The lab's primary mission is to conduct basic research of the atom's nucleus using the lab's unique particle accelerator, known as the Continuous Electron Beam Accelerator Facility (CEBAF). For more information visit https://www.jlab.org/
The periodic table at the LANL (Los Alamos National Laboratory) contains basic element information together with the history, source, properties, use, handling and more. The provenance data may be found from the link under the source name.
The periodic table contains NIST's critically-evaluated data on atomic properties of the elements. The provenance data that include data for atomic spectroscopy, X-ray and gamma ray, radiation dosimetry, nuclear physics, and condensed matter physics may be found from the link under the source name. Ref: https://www.nist.gov/pml/atomic-spectra-database
This section provides all form of data related to element Gold.
The element property data was retrieved from publications.