RADIUM

introduction

Numéro atomique: 88
Groupe: 2 or II A
Poids atomique: 226
Période: 7
Numero CAS: 7440-14-4

Classification

chalcogènes
Halogène
Gaz rare
lanthanides
actinides
Rare Earth Element
Groupe Platine Métal
Transuranium
Pas d'isotopes stables
Solide
Liquide
Gaz
Solide (prédit)

La description • Usages / Fonction

Radium was discovered in 1898 by M. and Mme. Curie in the pitchblende or uraninite of North Bohemia, where it occurs. There is about 1 g of radium in 7 tons of pitchblende. The element was isolated in 1911 by Mme. Curie and Debierne by the electrolysis of a solution of pure radium chloride, employing a mercury cathode; on distillation in an atmosphere of hydrogen this amalgam yielded the pure metal. Originally, radium was obtained from the rich pitchblende ore found at Joachimsthal, Bohemia. The carnotite sands of Colorado furnish some radium, but richer ores are found in the Republic of Zaire and the Great Bear Lake region of Canada. Radium is present in all uranium minerals, and could be extracted, if desired, from the extensive wastes of uranium processing. Large uranium deposits are located in Ontario, New Mexico, Utah, Australia, and elsewhere. Radium is obtained commercially as the bromide or chloride; it is doubtful if any appreciable stock of the isolated element now exists. The pure metal is brilliant white when freshly prepared, but blackens on exposure to air, probably due to formation of the nitride. It exhibits luminescence, as do its salts; it decomposes in water and is somewhat more volatile than barium. It is a member of the alkaline-earth group of metals. Radium imparts a carmine red color to a flame. Radium emits alpha, beta, and gamma rays and when mixed with beryllium produce neutrons. One gram of radium-226 undergoes 3.7 X 10^10 disintegrations per s. The curie (Ci) is defined as that amount of radioactivity which has the same disintegration rate as 1 g of radium-226. Twenty nine isotopes and one isomer are now known; radium-226, the common isotope, has a half-life of 1599 years. One gram of radium produces about 0.0001 mL (STP) of emanation, or radon gas, per day. This is pumped from the radium and sealed in minute tubes, which are used in the treatment of cancer and other diseases. One gram of radium yields about 4186 kJ per year. Radium is used in producing self-luminous paints, neutron sources, and in medicine for the treatment of disease. Some of the more recently discovered radioisotopes, such as cobalt-60, are now being used in place of radium. Some of these sources are much more powerful, and others are safer to use. Radium loses about 1% of its activity in 25 years, being transformed into elements of lower atomic weight. Lead is a final product of disintegration. Stored radium should be ventilated to prevent build-up of radon. Inhalation, injection, or body exposure to radium can cause cancer and other body disorders. The maximum permissible burden in the total body for radium-226 is 7400 becquerel. 1

Propriétés physiques

Point de fusion:2*  700 °C = 973.15 K = 1292 °F
Point d'ébullition:2
sublimation point:2 
Triple point:2 
Point critique:2 
Densité:3  5 g/cm3

* - at 1 atm

Configuration de l'électron

Configuration de l'électron: [Rn] 7s2
Bloque: s
Plus haut niveau d'énergie occupés: 7
Électrons de valence: 2

Nombres quantiques:

n = 7
ℓ = 0
m = 0
ms = -½

Bonding

Électronégativité (échelle de Pauling):4 0.9
Electropositivity (échelle de Pauling): 3.1

ionisation potentiel   eV 5  kJ/mol  
ionisation potentiel   eV 5  kJ/mol  
1 5.2784    509.3
ionisation potentiel   eV 5  kJ/mol  
2 10.14716    979.1

Thermochimie

Chaleur spécifique: 
Conductivité thermique: 18.6 (W/m)/K, 27°C 6
Température de fusion: 
Chaleur de vaporisation: 
État de la matière Enthalpie de formation (ΔHf°)7 Entropy (S°)7 Gibbs Free Energy (ΔGf°)7
(kcal/mol) (kJ/mol) (cal/K) (J/K) (kcal/mol) (kJ/mol)
(s) 0 0 17 71.128 0 0
(g) 38 158.992 42.15 176.3556 31 129.704

isotopes

Nuclide Masse 8 Demi vie 8 Spin nucléaire 8 Énergie de liaison
202Ra 202.00989(7) 2.6(21) ms [0.7(+33-3) ms] 0+ 1,561.56 MeV
203Ra 203.00927(9) 4(3) ms (3/2-) 1,569.63 MeV
204Ra 204.006500(17) 60(11) ms [59(+12-9) ms] 0+ 1,577.70 MeV
205Ra 205.00627(9) 220(40) ms [210(+60-40) ms] (3/2-) 1,585.77 MeV
206Ra 206.003827(19) 0.24(2) s 0+ 1,593.84 MeV
207Ra 207.00380(6) 1.3(2) s (5/2-,3/2-) 1,601.91 MeV
208Ra 208.001840(17) 1.3(2) s 0+ 1,609.98 MeV
209Ra 209.00199(5) 4.6(2) s 5/2- 1,618.06 MeV
210Ra 210.000495(16) 3.7(2) s 0+ 1,626.13 MeV
211Ra 211.000898(28) 13(2) s 5/2(-) 1,634.20 MeV
212Ra 211.999794(12) 13.0(2) s 0+ 1,651.59 MeV
213Ra 213.000384(22) 2.74(6) min 1/2- 1,650.34 MeV
214Ra 214.000108(10) 2.46(3) s 0+ 1,658.41 MeV
215Ra 215.002720(8) 1.55(7) ms (9/2+)# 1,666.48 MeV
216Ra 216.003533(9) 182(10) ns 0+ 1,674.56 MeV
217Ra 217.006320(9) 1.63(17) μs (9/2+) 1,682.63 MeV
218Ra 218.007140(12) 25.2(3) μs 0+ 1,690.70 MeV
219Ra 219.010085(9) 10(3) ms (7/2)+ 1,689.45 MeV
220Ra 220.011028(10) 17.9(14) ms 0+ 1,697.53 MeV
221Ra 221.013917(5) 28(2) s 5/2+ 1,705.60 MeV
222Ra 222.015375(5) 38.0(5) s 0+ 1,713.67 MeV
223Ra 223.0185022(27) 11.43(5) d 3/2+ 1,721.74 MeV
224Ra 224.0202118(24) 3.6319(23) d 0+ 1,720.50 MeV
225Ra 225.023612(3) 14.9(2) d 1/2+ 1,728.57 MeV
226Ra 226.0254098(25) 1600(7) a 0+ 1,736.64 MeV
227Ra 227.0291778(25) 42.2(5) min 3/2+ 1,744.71 MeV
228Ra 228.0310703(26) 5.75(3) a 0+ 1,743.47 MeV
229Ra 229.034958(20) 4.0(2) min 5/2(+) 1,751.54 MeV
230Ra 230.037056(13) 93(2) min 0+ 1,759.61 MeV
231Ra 231.04122(32)# 103(3) s (5/2+) 1,758.37 MeV
232Ra 232.04364(30)# 250(50) s 0+ 1,766.44 MeV
233Ra 233.04806(50)# 30(5) s 1/2+# 1,774.51 MeV
234Ra 234.05070(53)# 30(10) s 0+ 1,773.26 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. 8

Abondance

Terre - Seawater: 0.000000000089 mg/L 9
Terre -  Croûte:  0.0000009 mg/kg = 0.00000000009% 9

composés

Information de sécurité


Fiche signalétique - ACI Alloys, Inc.

Pour plus d'informations

Liens externes:

Sources

(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:25.
(2) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:132.
(3) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 4:39-4:96.
(4) - Dean, John A. Lange's Handbook of Chemistry, 11th ed.; McGraw-Hill Book Company: New York, NY, 1973; p 4:8-4:149.
(5) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 10:178 - 10:180.
(6) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:193, 12:219-220.
(7) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:123-6:137.
(8) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:107-6:122.
(9) - Dean, John A. Lange's Handbook of Chemistry, 12th ed.; McGraw-Hill Book Company: New York, NY, 1979; p 9:4-9:94.
(10) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009).
(11) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 14:17.