introduction
Groupe: 16 or VI A
Poids atomique: 209
Période: 6
Numero CAS: 7440-08-6
Classification
Pas d'isotopes stables
Solide
Liquide
Gaz
Solide (prédit)
La description • Usages / Fonction
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
Propriétés physiques
Point de fusion:3* 254 °C = 527.15 K = 489.2 °F
Configuration de l'électron: [Xe] 6s2 4f14 5d10 6p4
n = 6
Électronégativité (échelle de Pauling):5 2.0
Chaleur spécifique:
Terre - Seawater: 0.000000000000014 mg/L 12
Liens externes:
Journaux:
(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:23-4:24.
Point d'ébullition:3* 962 °C = 1235.15 K = 1763.6 °F
sublimation point:3
Triple point:3
Point critique:3
Densité:4 9.20 g/cm3
* - at 1 atm
Configuration de l'électron
Bloque: p
Plus haut niveau d'énergie occupés: 6
Électrons de valence: 6
Nombres quantiques:
ℓ = 1
mℓ = -1
ms = -½
Bonding
Electropositivity (échelle de Pauling): 2
Electron Affinity:6 1.9 eV
oxydation États: +4,2
Fonction de travail:7 4.6 eV = 7.3692E-19 J
ionisation potentiel
eV 8
kJ/mol
ionisation potentiel
eV 8
kJ/mol
ionisation potentiel
eV 8
kJ/mol
1
8.417
812.1
Thermochimie
Conductivité thermique: 20 (W/m)/K, 27°C 9
Température de fusion:
Chaleur de vaporisation:
État de la matière
Enthalpie de formation (ΔHf°)10
Entropy (S°)10
Gibbs Free Energy (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
isotopes
Nuclide
Masse 11
Demi vie 11
Spin nucléaire 11
Énergie de liaison
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
Les valeurs marquées # ne sont pas purement dérivées des données expérimentales, mais au moins en partie des tendances systématiques. Spins avec de faibles arguments d'affectation sont entre parenthèses. 11
Abondance
Terre -
Croûte:
0.0000000002 mg/kg = 0.00000000000002% 12
Information de sécurité
Fiche signalétique - ACI Alloys, Inc.
Pour plus d'informations
American Elements
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Chemical Elements
ChemGlobe
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Environmental Chemistry
(1) Richard B. Holtzman and Frank H. Ilcewicz, Science 153, 1259-1260 (1966)
Sources
(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.