PRATA

Introdução

Número atômico: 47
Grupo: 11 or I B
Peso atômico: 107.8682
Período: 5
Número CAS: 7440-22-4

Classificação

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

Descrição • Usos / Função

Silver has been known since ancient times. It is mentioned in Genesis. Slag dumps in Asia Minor and on islands in the Aegean Sea indicate thatman learned to separate silver from lead as early as 3000 B.C. Silver occurs native and in ores such as argentite (Ag2S) and horn silver (AgCl); lead,lead-zinc, copper, gold, and copper-nickel ores are principal sources. Mexico, Canada, Peru, and the U.S. are the principal silver producers in thewestern hemisphere. Silver is also recovered during electrolytic refining of copper. Commercial fine silver contains at least 99.9% silver. Purities of99.999+% are available commercially. Pure silver has a brilliant white metallic luster. It is a little harder than gold and is very ductile and malleable,being exceeded only by gold and perhaps palladium. Pure silver has the highest electrical and thermal conductivity of all metals, and possesses thelowest contact resistance. It is stable in pure air and water, but tarnishes when exposed to ozone, hydrogen sulfide, or air containing sulfur. The alloysof silver are important. Sterling silver is used for jewelry, silverware, etc. where appearance is paramount. This alloy contains 92.5% silver, theremainder being copper or some other metal. Silver is of utmost importance in photography, about 30% of the U.S. industrial consumption going intothis application. It is used for dental alloys. Silver is used in making solder and brazing alloys, electrical contacts, and high capacity silver-zinc andsilver-cadmium batteries. Silver paints are used for making printed circuits. It is used in mirror production and may be deposited on glass or metalsby chemical deposition, electrodeposition, or by evaporation. When freshly deposited, it is the best reflector of visible light known, but is rapidlytarnishes and loses much of its reflectance. It is a poor reflector of ultraviolet. Silver fulminate (Ag2C2N2O2), a powerful explosive, is sometimes formedduring the silvering process. Silver iodide is used in seeding clouds to produce rain. Silver chloride has interesting optical properties as it can be madetransparent; it also is a cement for glass. Silver nitrate, or lunar caustic, the most important silver compound, is used extensively in photography. Whilesilver itself is not considered to be toxic, most of its salts are poisonous. Natural silver contains two stable isotopes. Forty nine other radioactive isotopesand isomers are known. Silver compounds can be absorbed in the circulatory system and reduced silver deposited in the various tissues of the body.A condition, known as argyria, results, with a greyish pigmentation of the skin and mucous membranes. Silver has germicidal effects and kills manylower organisms effectively without harm to higher animals. Silver for centuries has been used traditionally for coinage by many countries of the world.In recent times, however, consumption of silver has at times greatly exceeded the output. In 1939, the price of silver was fixed by the U.S. Treasuryat 71¢/troy oz., and at 90.5¢/troy oz. in 1946. In November 1961 the U.S. Treasury suspended sales of nonmonetized silver, and the price stabilizedfor a time at about $1.29, the melt-down value of silver U.S. coins. The Coinage Act of 1965 authorized a change in the metallic composition of thethree U.S. subsidiary denominations to clad or composite type coins. This was the first change in U.S. coinage since the monetary system wasestablished in 1792. Clad dimes and quarters are made of an outer layer of 75% Cu and 25% Ni bonded to a central core of pure Cu. The compositionof the one- and five-cent pieces remains unchanged. One-cent coins are 95% Cu and 5% Zn. Five-cent coins are 75% Cu and 25% Ni. Old silver dollarsare 90% Ag and 10% Cu. Earlier subsidiary coins of 90% Ag and 10% Cu officially were to circulate alongside the clad coins; however, in practicethey have largely disappeared (Gresham’s Law), as the value of the silver is now greater than their exchange value. Silver coins of other countries havelargely been replaced with coins made of other metals. On June 24, 1968, the U.S. Government ceased to redeem U.S. Silver Certificates with silver.Since that time, the price of silver has fluctuated widely. As of January 1996, the price of silver was about $5.30/troy oz. (17¢/g); however the pricehas fluctuated considerably due to market instability. 1

• "...gold and silver have been used as free metals since prehistoric times." 2

Propriedades físicas

Ponto de fusão:3*  961.78 °C = 1234.93 K = 1763.204 °F
Ponto de ebulição:3* 2162 °C = 2435.15 K = 3923.6 °F
Ponto de sublimação:3 
Ponto Triplo:3 
Ponto crítico:3 
Densidade:4  10.5 g/cm3

* - at 1 atm

Configuração Electron

Configuração Electron:  *[Kr] 5s1 4d10
Quadra: d
Mais alto nível de energia Ocupado: 5
Elétrons de valência: 

Números quânticos:

n = 4
ℓ = 2
m = 2
ms = -½

Colagem

Eletronegatividade (escala Pauling):5 1.93
Electropositivity (escala Pauling): 2.07
Electron Affinity:6 1.302 eV
oxidação Unidos: +1
Função no trabalho:7 4.64 eV = 7.43328E-19 J

potencial de ionização   eV 8  kJ/mol  
1 7.5762    731.0
potencial de ionização   eV 8  kJ/mol  
2 21.49    2073.5
potencial de ionização   eV 8  kJ/mol  
3 34.83    3360.6

Termoquímica

Calor específico: 0.235 J/g°C 9 = 25.349 J/mol°C = 0.056 cal/g°C = 6.059 cal/mol°C
Condutividade térmica: 429 (W/m)/K, 27°C 10
Calor de fusão: 11.3 kJ/mol 11 = 104.8 J/g
Calor da vaporização: 250.58 kJ/mol 12 = 2323.0 J/g
Estado da matéria Entalpia de formação (ΔHf°)13 entropia (S°)13 Gibbs Energia Livre (ΔGf°)13
(kcal/mol) (kJ/mol) (cal/K) (J/K) (kcal/mol) (kJ/mol)
(s) 0 0 10.17 42.55128 0 0
(g) 68.01 284.55384 41.321 172.887064 58.72 245.68448
(s) 0.0 0 42.6 178.2384
(g) 284.9 1192.0216 173.0 723.832 246.0 1029.264

isótopos

nuclide Massa 14 Meia vida 14 spin nuclear 14 Energia de ligação
100Ag 99.91610(8) 2.01(9) min (5)+ 848.61 MeV
101Ag 100.91280(11) 11.1(3) min 9/2+ 862.27 MeV
102Ag 101.91169(3) 12.9(3) min 5+ 870.34 MeV
103Ag 102.908973(18) 65.7(7) min 7/2+ 887.72 MeV
104Ag 103.908629(6) 69.2(10) min 5+ 895.79 MeV
105Ag 104.906529(12) 41.29(7) d 1/2- 903.87 MeV
106Ag 105.906669(5) 23.96(4) min 1+ 911.94 MeV
107Ag 106.905097(5) ESTÁVEL 1/2- 920.01 MeV
108Ag 107.905956(5) 2.37(1) min 1+ 928.08 MeV
109Ag 108.904752(3) ESTÁVEL 1/2- 936.15 MeV
110Ag 109.906107(3) 24.6(2) s 1+ 944.22 MeV
111Ag 110.905291(3) 7.45(1) d 1/2- 952.29 MeV
112Ag 111.907005(18) 3.130(9) h 2(-) 960.37 MeV
113Ag 112.906567(18) 5.37(5) h 1/2- 968.44 MeV
114Ag 113.908804(27) 4.6(1) s 1+ 976.51 MeV
115Ag 114.90876(4) 20.0(5) min 1/2- 984.58 MeV
116Ag 115.91136(5) 2.68(10) min (2)- 983.34 MeV
117Ag 116.91168(5) 73.6(14) s [72.8(+20-7) s] 1/2-# 991.41 MeV
118Ag 117.91458(7) 3.76(15) s 1- 999.48 MeV
119Ag 118.91567(10) 6.0(5) s 1/2-# 1,007.55 MeV
120Ag 119.91879(8) 1.23(4) s 3(+#) 1,015.62 MeV
121Ag 120.91985(16) 0.79(2) s (7/2+)# 1,023.69 MeV
122Ag 121.92353(22)# 0.529(13) s (3+) 1,022.45 MeV
123Ag 122.92490(22)# 0.300(5) s (7/2+) 1,030.52 MeV
124Ag 123.92864(21)# 172(5) ms 3+# 1,038.59 MeV
125Ag 124.93043(32)# 166(7) ms (7/2+)# 1,037.35 MeV
126Ag 125.93450(32)# 107(12) ms 3+# 1,045.42 MeV
127Ag 126.93677(32)# 79(3) ms 7/2+# 1,053.49 MeV
128Ag 127.94117(32)# 58(5) ms 1,052.25 MeV
129Ag 128.94369(43)# 44(7) ms [46(+5-9) ms] 7/2+# 1,060.32 MeV
130Ag 129.95045(36)# ~50 ms 0+ 1,059.07 MeV
93Ag 92.94978(64)# 5# ms [>1.5 μs] 9/2+# 761.37 MeV
94Ag 93.94278(54)# 37(18) ms [26(+26-9) ms] 0+# 775.96 MeV
95Ag 94.93548(43)# 1.74(13) s (9/2+) 790.55 MeV
96Ag 95.93068(43)# 4.45(4) s (8+) 803.28 MeV
97Ag 96.92397(35) 25.3(3) s (9/2+) 817.87 MeV
98Ag 97.92157(7) 47.5(3) s (5+) 827.81 MeV
99Ag 98.91760(16) 124(3) s (9/2)+ 839.60 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. 14

reações

Abundância

Terra - Os compostos de origem: sulfides 17
Terra - A água do mar: 0.00004 mg/L 18
Terra -  crosta:  0.075 mg/kg = 0.0000075% 18
Terra -  Total:  44 ppb 19
Planeta Mercúrio) -  Total:  7.2 ppb 19
Vênus -  Total:  49 ppb 19
condritos - Total: ~0.09 (relative to 106 atoms of Si) 20

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 4:29.
(2) - Whitten, Kenneth W., Davis, Raymond E., and Peck, M. Larry. General Chemistry 6th ed.; Saunders College Publishing: Orlando, FL, 2000; p 905.
(3) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:132.
(4) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 4:39-4:96.
(5) - Dean, John A. Lange's Handbook of Chemistry, 11th ed.; McGraw-Hill Book Company: New York, NY, 1973; p 4:8-4:149.
(6) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 10:147-10:148.
(7) - Speight, James. Lange's Handbook of Chemistry, 16th ed.; McGraw-Hill Professional: Boston, MA, 2004; p 1:132.
(8) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 10:178 - 10:180.
(9) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:133.
(10) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:193, 12:219-220.
(11) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:123-6:137.
(12) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:107-6:122.
(13) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 5:5.
(14) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009).
(15) - Ebbing, Darrell D. General Chemistry 3rd ed.; Houghton Mifflin Company: Boston, MA, 1990; p 97.
(16) - Ebbing, Darrell D. General Chemistry 3rd ed.; Houghton Mifflin Company: Boston, MA, 1990; p 75.
(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.