Gold (Au)
transition-metalSolid
Peso atômico padrão
196,966569 uConfiguração eletrônica
[Xe] 6s1 4f14 5d10Ponto de fusão
1064,18 °CPonto de ebulição
2855,85 °CDensidade
1,9282e+4 kg/m³Estados de oxidação
−3, −2, −1, 0, +1, +2, +3, +5Eletronegatividade (Pauling)
2,54Energia de ionização (1ª)
9,225554 eVAno da descoberta
N/DRaio atômico
135 pmDetalhes
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.
Imagens
Propriedades
Física
- Raio atômico (empírico)
- 135 pm Comparar Raio atômico (empírico) de todos os elementos →
- Raio covalente
- 136 pm Comparar Raio covalente de todos os elementos →
- Raio de van der Waals
- 166 pm Comparar Raio de van der Waals de todos os elementos →
- Raio metálico
- 134 pm Comparar Raio metálico de todos os elementos →
- Densidade
- 1,9282 × 104 kg/m³ Comparar Densidade de todos os elementos →
- Volume molar
- 0,0102 L/mol
- Fase nas CNTP
- Sólido Comparar Fase nas CNTP de todos os elementos →
- Ponto de fusão
- 1064,18 °C Comparar Ponto de fusão de todos os elementos →
- Ponto de ebulição
- 2855,85 °C Comparar Ponto de ebulição de todos os elementos →
- Condutividade térmica
- 318 W/(m·K) Comparar Condutividade térmica de todos os elementos →
- Capacidade calorífica específica
- 0,129 J/(g·K) Comparar Capacidade calorífica específica de todos os elementos →
- Capacidade calorífica molar
- 25,418 J/(mol·K) Comparar Capacidade calorífica molar de todos os elementos →
- Estrutura cristalina
- Cúbica de faces centradas Comparar Estrutura cristalina de todos os elementos →
Química
- Eletronegatividade (Pauling)
- 2,54 Comparar Eletronegatividade (Pauling) de todos os elementos →
- Eletronegatividade (Allen)
- 1,92
- Afinidade eletrônica
- 2,3086 eV
- Energia de ionização (1ª)
- 9,225554 eV Comparar Energia de ionização (1ª) de todos os elementos →
- Energia de ionização (2ª)
- 20,20307 eV Comparar Energia de ionização (2ª) de todos os elementos →
- Energia de ionização (3ª)
- 30,000103 eV Comparar Energia de ionização (3ª) de todos os elementos →
- Energia de ionização (4ª)
- 45,000155 eV Comparar Energia de ionização (4ª) de todos os elementos →
- Energia de ionização (5ª)
- 60,000207 eV Comparar Energia de ionização (5ª) de todos os elementos →
- Estados de oxidação
- −3, −2, −1, 0, +1, +2, +3, +5 Comparar Estados de oxidação de todos os elementos →
- Elétrons de valência
- 11 Comparar Elétrons de valência de todos os elementos →
- Configuração eletrônica
- [Xe] 6s1 4f14 5d10
Termodinâmica
- Calor de fusão
- 0,13007203 eV Comparar Calor de fusão de todos os elementos →
- Calor de vaporização
- 3,358035 eV Comparar Calor de vaporização de todos os elementos →
- Calor de sublimação
- 3,814064 eV
- Calor de atomização
- 3,814064 eV
- Entalpia de atomização
- 3,816137 eV
Nuclear
- Prótons
- 79 Comparar Prótons de todos os elementos →
- Nêutrons
- 118 Comparar Nêutrons de todos os elementos →
- Isótopos conhecidos
- 43 Comparar Isótopos conhecidos de todos os elementos →
- Isótopos estáveis
- 1 Comparar Isótopos estáveis de todos os elementos →
- Isótopo mais estável
- Au-197
Abundância
- Abundância (crosta terrestre)
- 0,004 mg/kg Comparar Abundância (crosta terrestre) de todos os elementos →
- Abundância (oceano)
- 4 × 10−6 mg/L Comparar Abundância (oceano) de todos os elementos →
Estrutura cristalina
- Constante de rede a
- 408 pm
Estrutura eletrônica
- Elétrons por camada
- 2, 8, 18, 32, 18, 1 Comparar Elétrons por camada de todos os elementos →
Identificadores
- Número CAS
- 7440-57-5 Comparar Número CAS de todos os elementos →
- Símbolo de termo
- 2S1/2
- InChI
- InChI=1S/Au
- Chave InChI
- PCHJSUWPFVWCPO-UHFFFAOYSA-N
Configuração eletrônica Medido
Au: 4f¹⁴ 5d¹⁰ 6s¹[Xe] 4f¹⁴ 5d¹⁰ 6s¹1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s¹Modelo atômico
Os isótopos alteram o número de nêutrons, a massa e a estabilidade — não a configuração eletrônica de um átomo neutro.
Modelo atômico esquemático, sem escala.
Assinatura atômica
Espectro de emissão / absorção
Distribuição isotópica
| Número de massa | Massa atômica (u) | Abundância natural | Meia-vida |
|---|---|---|---|
| 197 Estável | 196,96656879 ± 0,00000071 | 100,0000% | Estável |
Fase / Estado
Motivo: 1039,2 °C abaixo do ponto de fusão (1064,18 °C)
Esquemático, sem escala
Pontos de transição de fase
Energias de transição
Energia necessária para fundir 1 mol no ponto de fusão
Energia necessária para vaporizar 1 mol no ponto de ebulição
Energia necessária para sublimar 1 mol no ponto de sublimação
Densidade
Em condições padrão
Em condições padrão
Espectros atômicos
Mostrando 10 de 79. Ordenado por carga do íon (ordem crescente).
Dados de linhas disponíveis ?
| Íon | Carga | Total de linhas | Probabilidades de transição | Designações dos níveis |
|---|---|---|---|---|
| Au I | 0 | 191 | 20 | 90 |
| Au II | +1 | 111 | 0 | 10 |
| Au III | +2 | 150 | 0 | 0 |
Dados de níveis disponíveis ?
| Íon | Carga | Níveis |
|---|---|---|
| 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 |
Raios iônicos
| Carga | Coordenação | Spin | Raio |
|---|---|---|---|
| +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 |
Compostos
Isótopos (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.
| Número de massa | Massa atômica (u) | Abundância natural | Meia-vida | Modo de decaimento | |
|---|---|---|---|---|---|
| 197 Estável | 196,96656879 ± 0,00000071 | 100,0000% | Estável | stable |
Propriedades ampliadas
Raios covalentes (dados ampliados)
- Raio covalente (Pyykkö)
- 124 pm
- Raio covalente (Pyykkö, ligação dupla)
- 121 pm
- Raio covalente (Pyykkö, ligação tripla)
- 123 pm
Raios de van der Waals
- Batsanov
- 210 pm
- Alvarez
- 232 pm
- UFF
- 329,3 pm
- MM3
- 243 pm
Raios atômicos e metálicos
- Raio atômico (Rahm)
- 226 pm
- Raio metálico (C12)
- 144 pm
Escalas de numeração
- Mendeleev
- 73
- Pettifor
- 70
- Glawe
- 66
Escalas de eletronegatividade
- Ghosh
- 0
- Miedema
- 5
- Gunnarsson–Lundqvist
- 5
- Robles–Bartolotti
- 4
Polarizabilidade e dispersão
- Polarizabilidade dipolar
- 36 a.u.
- Polarizabilidade dipolar (incerteza)
- 3 a.u.
- C₆ (Gould–Bučko)
- 427 Ha·Bohr6
Parâmetros de Miedema
- Volume molar de Miedema
- 10,2 cm3/mol
- Densidade eletrônica de Miedema
- 4
Risco de abastecimento e economia
- Concentração da produção
- 13
- Risco relativo de abastecimento
- 6
- Distribuição das reservas
- 15
- Estabilidade política (maior produtor)
- 24
- Estabilidade política (detentor das maiores reservas)
- 75
Transições de fase e alótropos
| Ponto de fusão | 1337,33 K |
| Ponto de ebulição | 3109,15 K |
Categorias de estados de oxidação
Dados de referência avançados
Constantes de blindagem (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 |
Detalhes dos raios cristalinos (4)
| Carga | CN | Spin | rcrystal (pm) | Origem |
|---|---|---|---|---|
| 1 | VI | 151 | Ahrens (1952) ionic radius, | |
| 3 | IVSQ | 82 | ||
| 3 | VI | 99 | Ahrens (1952) ionic radius, | |
| 5 | VI | 71 |
Modos de decaimento dos isótopos (71)
| Isótopo | Modo | Intensidade |
|---|---|---|
| 168 | p | — |
| 169 | p | — |
| 169 | A | — |
| 169 | B+ | — |
| 170 | p | 89% |
| 170 | A | 11% |
| 171 | p | 100% |
| 171 | A | — |
| 172 | A | 100% |
| 172 | p | — |
Fatores de espalhamento de raios 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 |
Dados adicionais
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
4×10-3 milligrams per kilogram
Referências (1)
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
4×10-6 milligrams per liter
Referências (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.
Referências (1)
- [6] Gold https://periodic.lanl.gov/79.shtml
Referências
(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.