Introduction
Group: 2 or II A
Atomic Weight: 226
Period: 7
CAS Number: 7440-14-4
Classification
No Stable Isotopes
Solid
Liquid
Gas
Solid (Predicted)
Description • Uses/Function
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
Physical Properties
Melting Point:2* 700 °C = 973.15 K = 1292 °F
Electron Configuration: [Rn] 7s2
n = 7
Electronegativity (Pauling scale):4 0.9
Specific Heat:
Earth - Seawater: 0.000000000089 mg/L 9
External Links:
(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:25.
Boiling Point:2*
Sublimation Point:2
Triple Point:2
Critical Point:2
Density:3 5 g/cm3
* - at 1 atm
Electron Configuration
Block: s
Highest Occupied Energy Level: 7
Valence Electrons: 2
Quantum Numbers:
ℓ = 0
mℓ = 0
ms = -½
Bonding
Electropositivity (Pauling scale): 3.1
Ionization Potential
eV 5
kJ/mol
Ionization Potential
eV 5
kJ/mol
1
5.2784
509.3
Ionization Potential
eV 5
kJ/mol
2
10.14716
979.1
Thermochemistry
Thermal Conductivity: 18.6 (W/m)/K, 27°C 6
Heat of Fusion:
Heat of Vaporization:
State of Matter
Enthalpy of 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
Mass 8
Half-Life 8
Nuclear Spin 8
Binding Energy
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
Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses. 8
Abundance
Earth -
Crust:
0.0000009 mg/kg = 0.00000000009% 9
Compounds
Safety Information
Material Safety Data Sheet - ACI Alloys, Inc.
For More Information
American Elements
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Sources
(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.