Gold (Au)
transition-metalSolid
Peso atomico standard
196,966569 uConfigurazione elettronica
[Xe] 6s1 4f14 5d10Punto di fusione
1064,18 °CPunto di ebollizione
2855,85 °CDensità
1,9282e+4 kg/m³Stati di ossidazione
−3, −2, −1, 0, +1, +2, +3, +5Elettronegatività (Pauling)
2,54Energia di ionizzazione (1ª)
9,225554 eVAnno della scoperta
N/DRaggio atomico
135 pmDettagli
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.
Immagini
Proprietà
Fisiche
- Raggio atomico (empirico)
- 135 pm Confronta Raggio atomico (empirico) di tutti gli elementi →
- Raggio covalente
- 136 pm Confronta Raggio covalente di tutti gli elementi →
- Raggio di van der Waals
- 166 pm Confronta Raggio di van der Waals di tutti gli elementi →
- Raggio metallico
- 134 pm Confronta Raggio metallico di tutti gli elementi →
- Densità
- 1,9282 × 104 kg/m³ Confronta Densità di tutti gli elementi →
- Volume molare
- 0,0102 L/mol
- Fase in condizioni STP
- Solido Confronta Fase in condizioni STP di tutti gli elementi →
- Punto di fusione
- 1064,18 °C Confronta Punto di fusione di tutti gli elementi →
- Punto di ebollizione
- 2855,85 °C Confronta Punto di ebollizione di tutti gli elementi →
- Conducibilità termica
- 318 W/(m·K) Confronta Conducibilità termica di tutti gli elementi →
- Capacità termica specifica
- 0,129 J/(g·K) Confronta Capacità termica specifica di tutti gli elementi →
- Capacità termica molare
- 25,418 J/(mol·K) Confronta Capacità termica molare di tutti gli elementi →
- Struttura cristallina
- Cubica a facce centrate Confronta Struttura cristallina di tutti gli elementi →
Chimiche
- Elettronegatività (Pauling)
- 2,54 Confronta Elettronegatività (Pauling) di tutti gli elementi →
- Elettronegatività (Allen)
- 1,92
- Affinità elettronica
- 2,3086 eV
- Energia di ionizzazione (1ª)
- 9,225554 eV Confronta Energia di ionizzazione (1ª) di tutti gli elementi →
- Energia di ionizzazione (2ª)
- 20,20307 eV Confronta Energia di ionizzazione (2ª) di tutti gli elementi →
- Energia di ionizzazione (3ª)
- 30,000103 eV Confronta Energia di ionizzazione (3ª) di tutti gli elementi →
- Energia di ionizzazione (4ª)
- 45,000155 eV Confronta Energia di ionizzazione (4ª) di tutti gli elementi →
- Energia di ionizzazione (5ª)
- 60,000207 eV Confronta Energia di ionizzazione (5ª) di tutti gli elementi →
- Stati di ossidazione
- −3, −2, −1, 0, +1, +2, +3, +5 Confronta Stati di ossidazione di tutti gli elementi →
- Elettroni di valenza
- 11 Confronta Elettroni di valenza di tutti gli elementi →
- Configurazione elettronica
- [Xe] 6s1 4f14 5d10
Termodinamiche
- Calore di fusione
- 0,13007203 eV Confronta Calore di fusione di tutti gli elementi →
- Calore di vaporizzazione
- 3,358035 eV Confronta Calore di vaporizzazione di tutti gli elementi →
- Calore di sublimazione
- 3,814064 eV
- Calore di atomizzazione
- 3,814064 eV
- Entalpia di atomizzazione
- 3,816137 eV
Nucleari
- Protoni
- 79 Confronta Protoni di tutti gli elementi →
- Neutroni
- 118 Confronta Neutroni di tutti gli elementi →
- Isotopi noti
- 43 Confronta Isotopi noti di tutti gli elementi →
- Isotopi stabili
- 1 Confronta Isotopi stabili di tutti gli elementi →
- Isotopo più stabile
- Au-197
Abbondanza
- Abbondanza (crosta terrestre)
- 0,004 mg/kg Confronta Abbondanza (crosta terrestre) di tutti gli elementi →
- Abbondanza (oceano)
- 4 × 10−6 mg/L Confronta Abbondanza (oceano) di tutti gli elementi →
Struttura cristallina
- Costante reticolare a
- 408 pm
Struttura elettronica
- Elettroni per guscio
- 2, 8, 18, 32, 18, 1 Confronta Elettroni per guscio di tutti gli elementi →
Identificativi
- Numero CAS
- 7440-57-5 Confronta Numero CAS di tutti gli elementi →
- Simbolo di termine
- 2S1/2
- InChI
- InChI=1S/Au
- Chiave InChI
- PCHJSUWPFVWCPO-UHFFFAOYSA-N
Configurazione elettronica Misurato
Au: 4f¹⁴ 5d¹⁰ 6s¹[Xe] 4f¹⁴ 5d¹⁰ 6s¹1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s¹Modello atomico
Gli isotopi modificano il numero di neutroni, la massa e la stabilità — non la configurazione elettronica di un atomo neutro.
Modello atomico schematico, non in scala.
Impronta atomica
Spettro di emissione / assorbimento
Distribuzione isotopica
| Numero di massa | Massa atomica (u) | Abbondanza naturale | Emivita |
|---|---|---|---|
| 197 Stabile | 196,96656879 ± 0,00000071 | 100,0000% | Stabile |
Fase / Stato
Motivo: 1039,2 °C sotto il punto di fusione (1064,18 °C)
Schema non in scala
Punti di transizione di fase
Energie di transizione
Energia necessaria per fondere 1 mol al punto di fusione
Energia necessaria per vaporizzare 1 mol al punto di ebollizione
Energia necessaria per sublimare 1 mol al punto di sublimazione
Densità
In condizioni standard
In condizioni standard
Spettri atomici
Sono visualizzati 10 di 79. Ordinamento per carica ionica crescente.
Righe disponibili ?
| Ione | Carica | Righe totali | Probabilità di transizione | Designazioni dei livelli |
|---|---|---|---|---|
| Au I | 0 | 191 | 20 | 90 |
| Au II | +1 | 111 | 0 | 10 |
| Au III | +2 | 150 | 0 | 0 |
Livelli disponibili ?
| Ione | Carica | Livelli |
|---|---|---|
| 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 |
Raggi ionici
| Carica | Coordinazione | Spin | Raggio |
|---|---|---|---|
| +1 | 6 | N/D | 137 pm |
| +3 | 4 | N/D | 68 pm |
| +3 | 6 | N/D | 85 pm |
| +5 | 6 | N/D | 56.99999999999999 pm |
Composti
Isotopi (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.
| Numero di massa | Massa atomica (u) | Abbondanza naturale | Emivita | Modalità di decadimento | |
|---|---|---|---|---|---|
| 197 Stabile | 196,96656879 ± 0,00000071 | 100,0000% | Stabile | stable |
Proprietà estese
Raggi covalenti (dati estesi)
- Raggio covalente (Pyykkö)
- 124 pm
- Raggio covalente (Pyykkö, legame doppio)
- 121 pm
- Raggio covalente (Pyykkö, legame triplo)
- 123 pm
Raggi di van der Waals
- Batsanov
- 210 pm
- Alvarez
- 232 pm
- UFF
- 329,3 pm
- MM3
- 243 pm
Raggi atomici e metallici
- Raggio atomico (Rahm)
- 226 pm
- Raggio metallico (C12)
- 144 pm
Scale di numerazione
- Mendeleev
- 73
- Pettifor
- 70
- Glawe
- 66
Scale di elettronegatività
- Ghosh
- 0
- Miedema
- 5
- Gunnarsson–Lundqvist
- 5
- Robles–Bartolotti
- 4
Polarizzabilità e dispersione
- Polarizzabilità dipolare
- 36 a.u.
- Polarizzabilità dipolare (inc.)
- 3 a.u.
- C₆ (Gould–Bučko)
- 427 Ha·Bohr6
Parametri di Miedema
- Volume molare di Miedema
- 10,2 cm3/mol
- Densità elettronica di Miedema
- 4
Rischio di approvvigionamento ed economia
- Concentrazione della produzione
- 13
- Rischio relativo di approvvigionamento
- 6
- Distribuzione delle riserve
- 15
- Stabilità politica (principale produttore)
- 24
- Stabilità politica (principale detentore di riserve)
- 75
Transizioni di fase e allotropi
| Punto di fusione | 1337,33 K |
| Punto di ebollizione | 3109,15 K |
Categorie degli stati di ossidazione
Dati di riferimento avanzati
Costanti di schermaggio (14)
| n | Orbitale | 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 |
Dettaglio dei raggi cristallini (4)
| Carica | CN | Spin | rcrystal (pm) | Origine |
|---|---|---|---|---|
| 1 | VI | 151 | Ahrens (1952) ionic radius, | |
| 3 | IVSQ | 82 | ||
| 3 | VI | 99 | Ahrens (1952) ionic radius, | |
| 5 | VI | 71 |
Modalità di decadimento degli isotopi (71)
| Isotopo | Modalità | Intensità |
|---|---|---|
| 168 | p | — |
| 169 | p | — |
| 169 | A | — |
| 169 | B+ | — |
| 170 | p | 89% |
| 170 | A | 11% |
| 171 | p | 100% |
| 171 | A | — |
| 172 | A | 100% |
| 172 | p | — |
Fattori di diffusione dei raggi X (506)
| Energia (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 |
Dati aggiuntivi
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
4×10-3 milligrams per kilogram
Riferimenti (1)
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
4×10-6 milligrams per liter
Riferimenti (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.
Riferimenti (1)
- [6] Gold https://periodic.lanl.gov/79.shtml
Riferimenti
(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.