POLÔNIO

Introdução

Número atômico: 84
Grupo: 16 or VI A
Peso atômico: 209
Período: 6
Número CAS: 7440-08-6

Classificação

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

Descrição • Usos / Função

Polonium was the first element discovered by Mme. Curie in 1898, while seeking the cause of radioactivity of pitchblende from Joachimsthal, Bohemia. The electroscope showed it separating with bismuth. Polonium is also called Radium F. Polonium is a very rare natural element. Uranium ores contain only about 100 mg of the element per ton. Its abundance is only about 0.2% of that of radium. In 1934, it was found that when natural bismuth (bismuth-209) was bombarded by neutrons, bismuth-210, the parent of polonium, was obtained. Milligram amounts of polonium may now be prepared this way, by using the high neutron fluxes of nuclear reactors. Polonium-210 is a low-melting, fairly volatile metal, 50% of which is vaporized in air in 45 hours at 55°C. It is an alpha emitter with a half-life of 138.39 days. A milligram emits as many alpha particles as 5 g of radium. The energy released by its decay is so large (140 W/g) that a capsule containing about half a gram reaches a temperature above 500°C. The capsule also presents a contact gamma-ray dose rate of 0.012 Gy/h. A few curies (1 curie = 3.7 X 10^10 Bq) of polonium exhibit a blue glow, caused by excitation of the surrounding gas. Because almost all alpha radiation is stopped within the solid source and its container, giving up its energy, polonium has attracted attention for uses as a lightweight heat source for thermoelectric power in space satellites. Thirty six isotopes and isomers of polonium are known, with atomic masses ranging from 192 to 218. All are radioactive. Polonium-210 is the most readily available. Isotopes of mass 209 (half-life 102 years) and mass 208 (half-life 2.9 years) can be prepared by alpha, proton, or deuteron bombardment of lead or bismuth in a cyclotron, but these are expensive to produce. Metallic polonium has been prepared from polonium hydroxide and some other polonium compounds in the presence of concentrated aqueous or anhydrous liquid ammonia. Two allotropic modifications are known to exist. Polonium is readily dissolved in dilute acids, but is only slightly soluble in alkalis. Polonium salts of organic acids char rapidly; halide amines are reduced to the metal. Polonium can be mixed or alloyed with beryllium to provide a source of neutrons. It has been used in devices for eliminating static charges in textile mills, etc.; however, beta sources are more commonly used and are less dangerous. It is also used on brushes for removing dust from photographic films. The polonium for these is carefully sealed and controlled, minimizing hazards to the user. Polonium-210 is very dangerous to handle in even milligram or microgram amounts, and special equipment and strict control is necessary. Damage arises from the complete absorption of the energy of the alpha particle into tissue. The maximum permissible body burden for ingested polonium is only 0.03 microcuries, which represents a particle weighing only 6.8 X 10^–12 g. Weight for weight it is about 2.5 X 10^11 times as toxic as hydrocyanic acid. The maximum allowable concentration for soluble polonium compounds in air is about 2 ´ 1011 microcuries/cm^3. Polonium-209 is available commercially on special order from the Oak Ridge National Laboratory at a cost of $3195/microcurie. 1

• "suggested that the isotope 210Po, a natural contaminant of tobacco and an α-particle emitter, might be at least partly responsible fo the incidence of cancer in smokers." 2

Propriedades físicas

Ponto de fusão:3*  254 °C = 527.15 K = 489.2 °F
Ponto de ebulição:3* 962 °C = 1235.15 K = 1763.6 °F
Ponto de sublimação:3 
Ponto Triplo:3 
Ponto crítico:3 
Densidade:4  9.20 g/cm3

* - at 1 atm

Configuração Electron

Configuração Electron: [Xe] 6s2 4f14 5d10 6p4
Quadra: p
Mais alto nível de energia Ocupado: 6
Elétrons de valência: 6

Números quânticos:

n = 6
ℓ = 1
m = -1
ms = -½

Colagem

Eletronegatividade (escala Pauling):5 2.0
Electropositivity (escala Pauling): 2
Electron Affinity:6 1.9 eV
oxidação Unidos: +4,2
Função no trabalho:7 4.6 eV = 7.3692E-19 J

potencial de ionização   eV 8  kJ/mol  
potencial de ionização   eV 8  kJ/mol  
potencial de ionização   eV 8  kJ/mol  
1 8.417    812.1

Termoquímica

Calor específico: 
Condutividade térmica: 20 (W/m)/K, 27°C 9
Calor de fusão: 
Calor da vaporização: 
Estado da matéria Entalpia de formação (ΔHf°)10 entropia (S°)10 Gibbs Energia Livre (ΔGf°)10
(kcal/mol) (kJ/mol) (cal/K) (J/K) (kcal/mol) (kJ/mol)
(g) -2.90 -12.1336 53.221 222.676664 -9.84 -41.17056
(s) 0 0 15.0 62.76 0 0
(g) 34.8 145.6032 45.13 188.82392 25.8 107.9472

isótopos

nuclide Massa 11 Meia vida 11 spin nuclear 11 Energia de ligação
188Po 187.999422(21) 430(180) μs [0.40(+20-15) ms] 0+ 1,461.00 MeV
189Po 188.998481(24) 5(1) ms 3/2-# 1,469.07 MeV
190Po 189.995101(14) 2.46(5) ms 0+ 1,477.15 MeV
191Po 190.994574(12) 22(1) ms 3/2-# 1,485.22 MeV
192Po 191.991335(13) 32.2(3) ms 0+ 1,493.29 MeV
193Po 192.99103(4) 420(40) ms [370(+46-40) ms] 3/2-# 1,501.36 MeV
194Po 193.988186(13) 0.392(4) s 0+ 1,518.75 MeV
195Po 194.98811(4) 4.64(9) s 3/2-# 1,526.82 MeV
196Po 195.985535(14) 5.56(12) s 0+ 1,534.89 MeV
197Po 196.98566(5) 53.6(10) s (3/2-) 1,542.96 MeV
198Po 197.983389(19) 1.77(3) min 0+ 1,551.03 MeV
199Po 198.983666(25) 5.48(16) min (3/2-) 1,559.10 MeV
200Po 199.981799(15) 11.5(1) min 0+ 1,567.17 MeV
201Po 200.982260(6) 15.3(2) min 3/2- 1,575.25 MeV
202Po 201.980758(16) 44.7(5) min 0+ 1,583.32 MeV
203Po 202.981420(28) 36.7(5) min 5/2- 1,591.39 MeV
204Po 203.980318(12) 3.53(2) h 0+ 1,599.46 MeV
205Po 204.981203(21) 1.66(2) h 5/2- 1,607.53 MeV
206Po 205.980481(9) 8.8(1) d 0+ 1,615.60 MeV
207Po 206.981593(7) 5.80(2) h 5/2- 1,623.67 MeV
208Po 207.9812457(19) 2.898(2) a 0+ 1,631.74 MeV
209Po 208.9824304(20) 102(5) a 1/2- 1,639.82 MeV
210Po 209.9828737(13) 138.376(2) d 0+ 1,647.89 MeV
211Po 210.9866532(14) 0.516(3) s 9/2+ 1,655.96 MeV
212Po 211.9888680(13) 299(2) ns 0+ 1,664.03 MeV
213Po 212.992857(3) 3.65(4) μs 9/2+ 1,662.79 MeV
214Po 213.9952014(16) 164.3(20) μs 0+ 1,670.86 MeV
215Po 214.9994200(27) 1.781(4) ms 9/2+ 1,678.93 MeV
216Po 216.0019150(24) 0.145(2) s 0+ 1,677.68 MeV
217Po 217.006335(7) 1.47(5) s 5/2+# 1,685.76 MeV
218Po 218.0089730(26) 3.10(1) min 0+ 1,693.83 MeV
219Po 219.01374(39)# 2# min [>300 ns] 7/2+# 1,692.58 MeV
220Po 220.01660(39)# 40# s [>300 ns] 0+ 1,700.66 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. 11

Abundância

Terra - A água do mar: 0.000000000000014 mg/L 12
Terra -  crosta:  0.0000000002 mg/kg = 0.00000000000002% 12

Informação de Segurança


Material Safety Data Sheet - ACI Alloys, Inc.

Para maiores informações

Links externos:

revistas:
(1) Richard B. Holtzman and Frank H. Ilcewicz, Science 153, 1259-1260 (1966)

Fontes

(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:23-4:24.
(2) - Zumdahl, Steven S. Chemistry, 4th ed.: Houghton Mifflin: Boston, 1997; p 916.
(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; pp 6:193, 12:219-220.
(10) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:123-6:137.
(11) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:107-6:122.
(12) - Dean, John A. Lange's Handbook of Chemistry, 12th ed.; McGraw-Hill Book Company: New York, NY, 1979; p 9:4-9:94.
(13) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009).
(14) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 14:17.