OURO

Introdução

Número atômico: 79
Grupo: 11 or I B
Peso atômico: 196.96655
Período: 6
Número CAS: 7440-57-5

Classificação

Calcogênio
halogênio
Gás nobre
Lantanóides
Actinóide
Terra-rara
Platinum Metal Group
Transuranium
Não Isótopos Estáveis
Sólido
Líquido
Gás
Sólido (previsto)

Descrição • Usos / Função

Known and highly valued from earliest times, gold is found in nature as the free metal and in tellurides; it is very widelydistributed and is almost always associated with quartz or pyrite. It occurs in veins and alluvial deposits, and is often separated from rocks and otherminerals by sluicing and panning operations. About two thirds of the world’s gold output comes from South Africa, and about two thirds of the totalU.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 sampleis taken. As yet, no method has been found for recovering gold from sea water profitably. 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 yellowcolor 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 mostmalleable and ductile metal; 1 oz. of gold can be beaten out to 300 sq ft. It is a soft metal and is usually alloyed to give it more strength. It is a good conductorof heat and electricity, and is unaffected by air and most reagents. It is used in coinage and is a standard for monetary systems in many countries. Itis 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 ofinfrared and is inert. Gold, like other precious metals, is measured in troy weight; when alloyed with other metals, the term carat is used to expressthe amount of gold present, 24 carats being pure gold. For many years the value of gold was set by the U.S. at $20.67/troy ounce; in 1934 this valuewas fixed by law at $35.00/troy ounce, 9/10th fine. On March 17, 1968, because of a gold crisis, a two-tiered pricing system was established wherebygold was still used to settle international accounts at the old $35.00/troy ounce price while the price of gold on the private market would be allowedto fluctuate. Since this time, the price of gold on the free market has fluctuated widely. The price of gold on the free market reached a price of $620/troy oz. in January 1980. The most common gold compounds are auric chloride (AuCl3) and chlorauric acid (HAuCl4), the latter being used inphotography for toning the silver image. Gold has forty six recognized isotopes and isomers; 198Au, with a half-life of 2.7 days, is used for treatingcancer and other diseases. Disodium aurothiomalate is administered intramuscularly as a treatment for arthritis. A mixture of one part nitric acid withthree of hydrochloric acid is called aqua regia (because it dissolved gold, the King of Metals). Gold is available commercially with a purity of99.999+%. For many years the temperature assigned to the freezing point of gold has been 1063.0°C; this has served as a calibration point for theInternational Temperature Scales (ITS-27 and ITS-48) and the International Practical Temperature Scale (IPTS-48). In 1968, a new InternationalPractical Temperature Scale (IPTS-68) was adopted, which demanded that the freezing point of gold be changed to 1064.43°C. In 1990 a newInternational Temperature Scale (ITS-90) was adopted bringing the t.p. (triple point) of H2O (t90 (°C)) to 0.01°C and the freezing point of gold to1064.18°C.The specific gravity of gold has been found to vary considerably depending on temperature, how the metal is precipitated, and cold-worked.As of January 1996, gold was priced at about $390/troy oz. ($12.50/g). 1

• "...gold and silver have been used as free metals since prehistoric times." 2
• "Pure gold, the most malleable of metals, is too soft to be used alone for most purposes. As gold leaf it is used for lettering and various decorative purposes. It is allyed with silver or copper. The proportion of gold in alloys is indicated by the number of carats fineness. Pure gold is 24 carats fine; 18-carat gold contains 18 parts by weight of gold and 6 parts of other metal. This carat should be distinguished from the carat used in weighing gems, which has been standardized at a weight of 200 milligrams. Our gold coins are 90 per cent gold and 10 per cent copper. Articles are gold-plated by an electroplating process, using as electrolyte a solution of the cyanide of potassium and gold. On gold-plated objects the outside layer is pure gold. Extremely thin coats, obtained by electrical deposition in a vacuum, are often used in plating." 3
• "In manuf[acturing] jewelry; in gold plating other metals; as a standard of currency; most frequently alloyed with silver and copper." 4

Propriedades físicas

Ponto de fusão:5*  1064.18 °C = 1337.33 K = 1947.524 °F
Ponto de ebulição:5* 2856 °C = 3129.15 K = 5172.8 °F
Ponto de sublimação:5 
Ponto Triplo:5 
Ponto crítico:5 
Densidade:6  19.3 g/cm3

* - at 1 atm

Configuração Electron

Configuração Electron: [Xe] 6s2 4f14 5d9
Quadra: d
Mais alto nível de energia Ocupado: 6
Elétrons de valência: 

Números quânticos:

n = 5
ℓ = 2
m = 1
ms = -½

Colagem

Eletronegatividade (escala Pauling):7 2.4
Electropositivity (escala Pauling): 1.6
Electron Affinity:8 2.30863 eV
oxidação Unidos: +3,1
Função no trabalho:9 5.32 eV = 8.52264E-19 J

potencial de ionização   eV 10  kJ/mol  
potencial de ionização   eV 10  kJ/mol  
1 9.2255    890.1
potencial de ionização   eV 10  kJ/mol  
2 20.5    1977.9

Termoquímica

Calor específico: 0.129 J/g°C 11 = 25.409 J/mol°C = 0.031 cal/g°C = 6.073 cal/mol°C
Condutividade térmica: 317 (W/m)/K, 27°C 12
Calor de fusão: 12.55 kJ/mol 13 = 63.7 J/g
Calor da vaporização: 334.4 kJ/mol 14 = 1697.8 J/g
Estado da matéria Entalpia de formação (ΔHf°)15 entropia (S°)15 Gibbs Energia Livre (ΔGf°)15
(kcal/mol) (kJ/mol) (cal/K) (J/K) (kcal/mol) (kJ/mol)
(s) 0 0 11.33 47.40472 0 0
(g) 87.5 366.1 43.115 180.39316 78.0 326.352

isótopos

nuclide Massa 16 Meia vida 16 spin nuclear 16 Energia de ligação
169Au 168.99808(32)# 150# μs 1/2+# 1,311.56 MeV
170Au 169.99612(22)# 310(50) μs [286(+50-40) μs] (2-) 1,319.63 MeV
171Au 170.991879(28) 17 μs (1/2+) 1,327.70 MeV
172Au 171.99004(17)# 6.3 ms high 1,335.77 MeV
173Au 172.986237(28) 20 ms (1/2+) 1,353.16 MeV
174Au 173.98476(11)# 120 ms low 1,361.23 MeV
175Au 174.98127(5) 185 ms 1/2+# 1,369.30 MeV
176Au 175.98010(11)# 1.08(17) s [0.84(+17-14) s] (5-) 1,377.37 MeV
177Au 176.976865(14) 1.462(32) s (1/2+,3/2+) 1,394.76 MeV
178Au 177.97603(6) 2.6(5) s 1,402.83 MeV
179Au 178.973213(18) 3.3 s 5/2-# 1,410.90 MeV
180Au 179.972521(23) 8.1(3) s 1,418.97 MeV
181Au 180.970079(21) 13.7(14) s (3/2-) 1,427.05 MeV
182Au 181.969618(22) 15.5(5) s (2+) 1,444.43 MeV
183Au 182.967593(11) 42.8(10) s (5/2)- 1,452.50 MeV
184Au 183.967452(24) 20.6(9) s 5+ 1,460.57 MeV
185Au 184.965789(28) 4.25(6) min 5/2- 1,468.65 MeV
186Au 185.965953(23) 10.7(5) min 3- 1,476.72 MeV
187Au 186.964568(27) 8.4(3) min 1/2+ 1,484.79 MeV
188Au 187.965324(22) 8.84(6) min 1(-) 1,492.86 MeV
189Au 188.963948(22) 28.7(3) min 1/2+ 1,500.93 MeV
190Au 189.964700(17) 42.8(10) min 1- 1,509.00 MeV
191Au 190.96370(4) 3.18(8) h 3/2+ 1,517.07 MeV
192Au 191.964813(17) 4.94(9) h 1- 1,525.15 MeV
193Au 192.964150(11) 17.65(15) h 3/2+ 1,533.22 MeV
194Au 193.965365(11) 38.02(10) h 1- 1,541.29 MeV
195Au 194.9650346(14) 186.098(47) d 3/2+ 1,549.36 MeV
196Au 195.966570(3) 6.1669(6) d 2- 1,557.43 MeV
197Au 196.9665687(6) ESTÁVEL 3/2+ 1,565.50 MeV
198Au 197.9682423(6) 2.69517(21) d 2- 1,573.57 MeV
199Au 198.9687652(6) 3.139(7) d 3/2+ 1,581.64 MeV
200Au 199.97073(5) 48.4(3) min 1(-) 1,580.40 MeV
201Au 200.971657(3) 26(1) min 3/2+ 1,588.47 MeV
202Au 201.97381(18) 28.8(19) s (1-) 1,596.54 MeV
203Au 202.975155(3) 53(2) s 3/2+ 1,604.61 MeV
204Au 203.97772(22)# 39.8(9) s (2-) 1,612.69 MeV
205Au 204.97987(32)# 31(2) s 3/2+ 1,620.76 MeV
Os valores marcados # não são puramente derivado a partir de dados experimentais, mas, pelo menos, parcialmente a partir de tendências sistemáticas. Gira com argumentos de atribuição fracos estão entre parênteses. 16

Abundância

Terra - Os compostos de origem: uncombined 17
Terra - A água do mar: 0.004 mg/L 18
Terra -  crosta:  0.004 mg/kg = 0.0000004% 18
Terra -  Total:  257 ppb 19
Planeta Mercúrio) -  Total:  516 ppm 19
Vênus -  Total:  250 ppb 19
condritos - Total: 0.18 (relative to 106 atoms of Si) 20
Corpo humano - Total: 0.00001% 21

compostos

preços





Informação de Segurança


Material Safety Data Sheet - ACI Alloys, Inc.

Para maiores informações

Links externos:

revistas:
(1) Moyer, Michael. How Much is Left?. Scientific American, September 2010, pp 74-81.

Fontes

(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:13-4:14.
(2) - Whitten, Kenneth W., Davis, Raymond E., and Peck, M. Larry. General Chemistry 6th ed.; Saunders College Publishing: Orlando, FL, 2000; p 905.
(3) - Brownlee, Raymond B., Fuller, Robert W., and Whitsit, Jesse E. Elements of Chemistry; Allyn and Bacon: Boston, Massachusetts, 1959; pp 543-4.
(4) - The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals, 13th ed.; Budavari, S.; O'Neil, M.J.; Smith, A.; Heckelman, P. E.; Kinneary, J. F., Eds.; Merck & Co.: Whitehouse Station, NJ, 2001; entry 4529.
(5) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:132.
(6) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 4:39-4:96.
(7) - Dean, John A. Lange's Handbook of Chemistry, 11th ed.; McGraw-Hill Book Company: New York, NY, 1973; p 4:8-4:149.
(8) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 10:147-10:148.
(9) - Speight, James. Lange's Handbook of Chemistry, 16th ed.; McGraw-Hill Professional: Boston, MA, 2004; p 1:132.
(10) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 10:178 - 10:180.
(11) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:133.
(12) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:193, 12:219-220.
(13) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:123-6:137.
(14) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:107-6:122.
(15) - Dean, John A. Lange's Handbook of Chemistry, 12th ed.; McGraw-Hill Book Company: New York, NY, 1979; p 9:4-9:94.
(16) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009).
(17) - Silberberg, Martin S. Chemistry: The Molecular Nature of Matter and Change, 4th ed.; McGraw-Hill Higher Education: Boston, MA, 2006, p 965.
(18) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 14:17.
(19) - Morgan, John W. and Anders, Edward, Proc. Natl. Acad. Sci. USA 77, 6973-6977 (1980)
(20) - Brownlow, Arthur. Geochemistry; Prentice-Hall, Inc.: Englewood Cliffs, NJ, 1979, pp 15-16.
(21) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 7:17.