SELENIO

Introducción

Número atómico: 34
Grupo: 16 or VI A
Peso atomico: 78.96
Período: 4
Número CAS: 7782-49-2

Clasificación

chalcogen
halógeno
Gas noble
Lantanoides
Actinoides
Elemento de tierras raras
Platino Metal Group
transuranium
No hay isótopos estables
Sólido
Líquido
Gas
Sólido (Predicho)

Descripción • Usos / Función

Discovered by Berzelius in 1817, who found it associated with tellurium, named for the earth. Selenium is found in a few rare minerals,such as crooksite and clausthalite. In years past it has been obtained from flue dusts remaining from processing copper sulfide ores, but the anode mudsfrom electrolytic copper refineries now provide the source of most of the world’s selenium. Selenium is recovered by roasting the muds with soda orsulfuric acid, or by smelting them with soda and niter. Selenium exists in several allotropic forms. Three are generally recognized, but as many as sixhave been claimed. Selenium can be prepared with either an amorphous or crystalline structure. The color of amorphous selenium is either red, inpowder form, or black, in vitreous form. Crystalline monoclinic selenium is a deep red; crystalline hexagonal selenium, the most stable variety, is ametallic gray. Natural selenium contains six stable isotopes. Twenty four other isotopes and isomers have been characterized. The element is a memberof the sulfur family and resembles sulfur both in its various forms and in its compounds. Selenium exhibits both photovoltaic action, where light isconverted directly into electricity, and photoconductive action, where the electrical resistance decreases with increased illumination. These propertiesmake selenium useful in the production of photocells and exposure meters for photographic use, as well as solar cells. Selenium is also able to converta.c. electricity to d.c., and is extensively used in rectifiers. Below its melting point selenium is a p-type semiconductor and is finding many uses inelectronic and solid-state applications. It is used in Xerography for reproducing and copying documents, letters, etc. It is used by the glass industryto decolorize glass and to make ruby-colored glasses and enamels. It is also used as a photographic toner, and as an additive to stainless steel. Elementalselenium has been said to be practically nontoxic and is considered to be an essential trace element; however, hydrogen selenide and other seleniumcompounds are extremely toxic, and resemble arsenic in their physiological reactions. Hydrogen selenide in a concentration of 1.5 ppm is intolerableto man. Selenium occurs in some soils in amounts sufficient to produce serious effects on animals feeding on plants, such as locoweed, grown in suchsoils. Selenium is priced at about $150/kg. It is also available in high-purity form at a cost of about $250/kg (99.999%). 1

• "toxicity has long been known" 2
• "is known to be physiologically important (it is involved in the activity of vitamin E and certain enzymes)" 3
• "deficiency has been shown to be connected to the occurrence of congestive heart failure" 4
• "considered to be an antioxidant nutrient because it is present in enzymes that help protect against toxic species of oxygen and free radicals. Selenium deficiency is a major public health problem in certain parts of China, where it increases the risk of heart disease, bone and joint disorders, and liver cancer. Selenium is currently under intensive investigation as a possible protector against cancer." 5
• "used in photocopy machines and in solar cells." 6

Propiedades físicas

Form:7 vitreous
Punto de fusion:7*  180 °C = 453.15 K = 356 °F
Punto de ebullición:7* 685 °C = 958.15 K = 1265 °F
Punto de sublimación:7 
Triple punto:7 
Punto crítico:7 1493 °C = 1766.15 K = 2719.4 °F 7
Form:7 gray
Punto de fusion:7*  220.5 °C = 493.65 K = 428.9 °F
Punto de ebullición:7* 685 °C = 958.15 K = 1265 °F
Punto de sublimación:7 
Triple punto:7 
Punto crítico:7 1493 °C = 1766.15 K = 2719.4 °F 7
Densidad:8  4.39 (alpha)/4.81 (gray)/4.28 (vitreous) g/cm3

* - at 1 atm

Configuración electronica

Configuración electronica: [Ar] 4s2 3d10 4p4
Bloquear: p
Ocupado más alto nivel de energía: 4
Electrones de valencia: 6

Números cuánticos:

n = 4
ℓ = 1
m = -1
ms = -½

Vinculación

electronegatividad (escala de Pauling):9 2.55
Electropositivity (escala de Pauling): 1.45
Afinidad electronica:10 2.020670 eV
estados de oxidación: +4,-2,+6
Función del trabajo:11 5.9 eV = 9.4518E-19 J

potencial de ionización   eV 12  kJ/mol  
1 9.75238    941.0
2 21.19    2044.5
potencial de ionización   eV 12  kJ/mol  
3 30.8204    2973.7
4 42.945    4143.6
potencial de ionización   eV 12  kJ/mol  
5 68.3    6589.9
6 81.7    7882.8
7 155.4    14993.8

termoquímica

Calor especifico: 0.321 J/g°C 13 = 25.346 J/mol°C = 0.077 cal/g°C = 6.058 cal/mol°C
Conductividad térmica: 2.04 (W/m)/K, 27°C 14
Calor de fusión: 6.694 kJ/mol 15 = 84.8 J/g
Calor de vaporización: 37.7 kJ/mol 16 = 477.5 J/g
Estado de la materia Entalpía de formación (ΔHf°)17 entropía (S°)17 Energía libre de Gibbs (ΔGf°)17
(kcal/mol) (kJ/mol) (cal/K) (J/K) (kcal/mol) (kJ/mol)
(s hexagonal black) 0 0 10.144 42.442496 0 0
(g) 54.27 227.06568 42.21 176.60664 44.71 187.06664

isótopos

nucleido Masa 18 Media vida 18 spin nuclear 18 Energía de unión
65Se 64.96466(64)# <50 ms 3/2-# 531.57 MeV
66Se 65.95521(32)# 33(12) ms 0+ 548.02 MeV
67Se 66.95009(21)# 133(11) ms 5/2-# 560.75 MeV
68Se 67.94180(4) 35.5(7) s 0+ 577.21 MeV
69Se 68.93956(4) 27.4(2) s (1/2-) 587.14 MeV
70Se 69.93339(7) 41.1(3) min 0+ 600.80 MeV
71Se 70.93224(3) 4.74(5) min 5/2- 609.80 MeV
72Se 71.927112(13) 8.40(8) d 0+ 622.53 MeV
73Se 72.926765(11) 7.15(8) h 9/2+ 631.54 MeV
74Se 73.9224764(18) ESTABLE 0+ 643.33 MeV
75Se 74.9225234(18) 119.779(4) d 5/2+ 651.40 MeV
76Se 75.9192136(18) ESTABLE 0+ 662.27 MeV
77Se 76.9199140(18) ESTABLE 1/2- 670.34 MeV
78Se 77.9173091(18) ESTABLE 0+ 680.28 MeV
79Se 78.9184991(18) 2.95(38)E+5 a 7/2+ 687.42 MeV
80Se 79.9165213(21) ESTABLE 0+ 697.35 MeV
81Se 80.9179925(22) 18.45(12) min 1/2- 704.49 MeV
82Se 81.9166994(22) 97(5)E+18 a 0+ 713.49 MeV
83Se 82.919118(4) 22.3(3) min 9/2+ 718.77 MeV
84Se 83.918462(16) 3.1(1) min 0+ 727.77 MeV
85Se 84.92225(3) 31.7(9) s (5/2+)# 732.12 MeV
86Se 85.924272(17) 15.3(9) s 0+ 738.33 MeV
87Se 86.92852(4) 5.50(12) s (5/2+)# 742.67 MeV
88Se 87.93142(5) 1.53(6) s 0+ 747.95 MeV
89Se 88.93645(32)# 0.41(4) s (5/2+)# 751.36 MeV
90Se 89.93996(43)# 300# ms [>300 ns] 0+ 756.64 MeV
91Se 90.94596(54)# 270(50) ms 1/2+# 759.12 MeV
92Se 91.94992(64)# 100# ms [>300 ns] 0+ 763.47 MeV
93Se 92.95629(86)# 50# ms [>300 ns] 1/2+# 765.02 MeV
94Se 93.96049(86)# 20# ms [>300 ns] 0+ 769.36 MeV
Los valores marcados con # no son puramente derivan de los datos experimentales, pero al menos en parte, de las tendencias sistemáticas. Hace girar con débiles argumentos de asignación se incluyen entre paréntesis. 18

reacciones

Abundancia

Tierra - Los compuestos de origen: sulfides 19
Tierra - Agua de mar: 0.0002 mg/L 20
Tierra -  Corteza:  0.05 mg/kg = 0.000005% 20
Tierra -  Total:  9.6 ppm 21
Planeta mercurio) -  Total:  0.79 ppm 21
Venus -  Total:  5.4 ppm 21
condritas - Total: 19 (relative to 106 atoms of Si) 22

Compuestos

Información de seguridad


Ficha de datos de seguridad de materiales - ACI Alloys, Inc.

Para más información

Enlaces externos:

Fuentes

(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:28.
(2) - Zumdahl, Steven S. Chemistry, 4th ed.: Houghton Mifflin: Boston, 1997; p 916.
(3) - Zumdahl, Steven S. Chemistry, 4th ed.: Houghton Mifflin: Boston, 1997; p 916.
(4) - Zumdahl, Steven S. Chemistry, 4th ed.: Houghton Mifflin: Boston, 1997; p 916.
(5) - Whitten, Kenneth W., Davis, Raymond E., and Peck, M. Larry. General Chemistry 6th ed.; Saunders College Publishing: Orlando, FL, 2000; p 927.
(6) - Whitten, Kenneth W., Davis, Raymond E., and Peck, M. Larry. General Chemistry 6th ed.; Saunders College Publishing: Orlando, FL, 2000; p 953.
(7) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:132.
(8) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 4:39-4:96.
(9) - Dean, John A. Lange's Handbook of Chemistry, 11th ed.; McGraw-Hill Book Company: New York, NY, 1973; p 4:8-4:149.
(10) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 10:147-10:148.
(11) - Speight, James. Lange's Handbook of Chemistry, 16th ed.; McGraw-Hill Professional: Boston, MA, 2004; p 1:132.
(12) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 10:178 - 10:180.
(13) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:133.
(14) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:193, 12:219-220.
(15) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:123-6:137.
(16) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:107-6:122.
(17) - Dean, John A. Lange's Handbook of Chemistry, 12th ed.; McGraw-Hill Book Company: New York, NY, 1979; p 9:4-9:94.
(18) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009).
(19) - Silberberg, Martin S. Chemistry: The Molecular Nature of Matter and Change, 4th ed.; McGraw-Hill Higher Education: Boston, MA, 2006, p 965.
(20) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 14:17.
(21) - Morgan, John W. and Anders, Edward, Proc. Natl. Acad. Sci. USA 77, 6973-6977 (1980)
(22) - Brownlow, Arthur. Geochemistry; Prentice-Hall, Inc.: Englewood Cliffs, NJ, 1979, pp 15-16.