Difference between revisions of "Radium" - New World Encyclopedia

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In 1902, Marie Curie and [[Andre Debierne]]* isolated radium in its pure [[metal]]lic form. Their method involved [[electrolysis]] of a solution of pure radium [[chloride]]*, using a [[mercury (element)|mercury]] [[electrolysis|cathode]], and [[distillation]]* the product in an atmosphere of [[hydrogen]] gas.
 
In 1902, Marie Curie and [[Andre Debierne]]* isolated radium in its pure [[metal]]lic form. Their method involved [[electrolysis]] of a solution of pure radium [[chloride]]*, using a [[mercury (element)|mercury]] [[electrolysis|cathode]], and [[distillation]]* the product in an atmosphere of [[hydrogen]] gas.
  
Historically, the radioactive decay products of radium were known as Radium A, B, C, and so forth. These are now known to be isotopes of other elements, as follows.
+
Historically, the radioactive decay products of radium were labeled Radium A, B, C, and so forth (see [[#Radioactivity|Radioactivity]] below). These are now recognized as isotopes of other elements. On February 4, 1936, radium E became the first [[radioactive]] element to be made synthetically.
 
 
:Radium emanation: radon-222
 
:Radium A: [[polonium]]-218
 
:Radium B: [[lead]]-214
 
:Radium C: [[bismuth]]-214
 
:Radium C<sub>1</sub>: polonium-214
 
:Radium C<sub>2</sub>: [[thallium]]-210
 
:Radium D: lead-210
 
:Radium E: bismuth-210
 
:Radium F: polonium-210
 
 
 
On February 4, 1936, radium E became the first [[radioactive]] element to be made synthetically.
 
  
 
During the 1930s, it was found that workers exposed to radium when handling [[luminescence|luminescent]]* paints suffered from serious health problems, including sores, [[anemia]]*, and bone [[cancer]]. This use of radium was stopped soon afterward. The reason for this problem is that the body treats radium as though it were [[calcium]]. Thus, radium becomes deposited in the bones, where radioactivity degrades the [[marrow]]* and damages bone cells. [[Marie Curie]]'s premature death has been attributed to her extensive work with radium.
 
During the 1930s, it was found that workers exposed to radium when handling [[luminescence|luminescent]]* paints suffered from serious health problems, including sores, [[anemia]]*, and bone [[cancer]]. This use of radium was stopped soon afterward. The reason for this problem is that the body treats radium as though it were [[calcium]]. Thus, radium becomes deposited in the bones, where radioactivity degrades the [[marrow]]* and damages bone cells. [[Marie Curie]]'s premature death has been attributed to her extensive work with radium.
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Radium is intensely radioactive, emitting three types of radiation: [[alpha particles]], [[beta particles]], and [[gamma rays]]. When mixed with [[beryllium]], radium produces [[neutron]]s. Another remarkable property of radium preparations is that they keep themselves warmer than their surroundings.
 
Radium is intensely radioactive, emitting three types of radiation: [[alpha particles]], [[beta particles]], and [[gamma rays]]. When mixed with [[beryllium]], radium produces [[neutron]]s. Another remarkable property of radium preparations is that they keep themselves warmer than their surroundings.
  
When freshly prepared, pure radium metal is brilliant white, but blackens when exposed to air (probably due to [[nitride]] formation). Radium is [[luminescence|luminescent]] (giving a faint blue color), corrodes in [[water]] to form [[radium hydroxide]] and is slightly more volatile than [[barium]].
+
Radium is [[luminescence|luminescent]]*, giving a faint blue color, and is slightly more volatile than [[barium]]. Like other alkaline earth metals, it reacts with [[water]] to form the hydroxide, which is alkaline.
  
 
=== Isotopes ===
 
=== Isotopes ===
Radium has 25 different [[isotope]]s, four of which are found in nature, with radium-226 being the most common. Ra-223, Ra-224, Ra-226 and Ra-228 are all generated in the decay of either [[Uranium|U]] or [[Thorium|Th]]. Ra-226 is a product of U-238 decay, and is the longest-lived isotope of radium with a [[half-life]] of 1602 years; next longest is Ra-228, a product of Th-232 breakdown, with a half-life of 6.7 years.
+
 
 +
Radium has 25 known [[isotope]]s, four of which&mdash;Ra-223, Ra-224, Ra-226, and Ra-228&mdash;are are found in nature and are generated by the decay of [[uranium]] or [[thorium]]. The common isotope is Ra-226, a product of U-238 decay. It is the longest-lived isotope of radium, with a [[half-life]]* of 1,602 years. The next longest-lived isotope is Ra-228, a product of Th-232 breakdown, with a half-life of 6.7 years.
  
 
=== Radioactivity ===
 
=== Radioactivity ===
Radium is over one million times more radioactive than the same mass of [[uranium]]. Its decay occurs in at least seven stages; the successive main products have been studied and were called radium emanation or exradio (this is [[radon]]), radium A ([[polonium]]), radium B ([[lead]]), radium C ([[bismuth]]), etc. (The radon is a heavy gas, the later products are solids.) These products are themselves radioactive elements, each with an atomic weight a little lower than its predecessor.
 
  
Radium loses about 1% of its activity in 25 years, being transformed into elements of lower atomic weight with [[lead]] being a final product of disintegration.
+
Radium is over one million times more radioactive than the same mass of [[uranium]]. It loses about 1% of its activity in 25 years, being transformed into elements of lower atomic weight. The final product of disintegration is [[lead]].
 +
 
 +
The decay of radium occurs in stages. The successive main products were called radium emanation (or exradio), radium A, radium B, radium C, and so forth. These products have been studied and are now known to be isotopes of other elements, as follows.
 +
 
 +
:Radium emanation: [[radon]]-222
 +
:Radium A: [[polonium]]-218
 +
:Radium B: [[lead]]-214
 +
:Radium C: [[bismuth]]-214
 +
:Radium C<sub>1</sub>: polonium-214
 +
:Radium C<sub>2</sub>: [[thallium]]-210
 +
:Radium D: lead-210
 +
:Radium E: bismuth-210
 +
:Radium F: polonium-210
  
The SI unit of radioactivity is the [[becquerel]] (Bq), equal to one disintegration per second.  The [[curie]] is a non-SI unit defined as that amount of radioactivity which has the same disintegration rate as 1 gram of Ra-226 (3.7 x 10<sup>10</sup> disintegrations per second, or 37 GBq).
+
The SI unit of radioactivity is the [[becquerel]] (Bq), corresponding to one disintegration per second.  The [[curie]]*, a non-SI unit, is defined as the amount of radioactivity that has the same disintegration rate as 1 gram of Ra-226 (3.7 x 10<sup>10</sup> disintegrations per second, or 37 GBq).
  
 
== Compounds ==
 
== Compounds ==
Its [[chemical compound|compound]]s <!-- (which are short lived) (Why should they be short lived?? Not shorter than Radium itself!) —> [[color]] flames [[crimson|crimson carmine]] (rich red or crimson color with a shade of purple) and give a characteristic [[electromagnetic spectrum|spectrum]]. Due to its geologically short [[half life]] and intense radioactivity, radium compounds are quite rare, occurring almost exclusively in uranium ores.
 
*[[radium fluoride]] (Ra[[florine|F]]<sub>2</sub>)
 
*[[radium chloride]] (Ra[[chlorine|Cl]]<sub>2</sub>)
 
*[[radium bromide]] (Ra[[bromine|Br]]<sub>2</sub>)
 
*[[radium iodide]] (Ra[[iodine|I]]<sub>2</sub>)
 
*[[radium oxide]] (Ra[[oxygen|O]])
 
  
''See also [[:Category:Radium compounds|radium compounds]].''
+
The [[chemical compound|compound]]s of radium color flames [[crimson|crimson carmine]]* (rich red or crimson color with a shade of purple) and give characteristic [[electromagnetic spectrum|spectra]]. Given that radium has a geologically short [[half-life]]* and intense radioactivity, its compounds are quite rare, occurring almost exclusively in uranium ores. Some compounds of radium are its oxide (Ra[[oxygen|O]]), fluoride (Ra[[florine|F]]<sub>2</sub>), chloride (Ra[[chlorine|Cl]]<sub>2</sub>), bromide (Ra[[bromine|Br]]<sub>2</sub>), and iodide (Ra[[iodine|I]]<sub>2</sub>).
  
 
== Applications ==
 
== Applications ==

Revision as of 17:57, 9 October 2006

88 franciumradiumactinium
Ba

Ra

Ubn
Ra-TableImage.png
periodic table
General
Name, Symbol, Number radium, Ra, 88
Chemical series alkaline earth metals
Group, Period, Block 2, 7, s
Appearance silvery white metallic
Atomic mass (226) g/mol
Electron configuration [Rn] 7s2
Electrons per shell 2, 8, 18, 32, 18, 8, 2
Physical properties
Phase solid
Density (near r.t.) 5.5 g/cm³
Melting point 973 K
(700 °C, 1292 °F)
Boiling point 2010 K
(1737 °C, 3159 °F)
Heat of fusion 8.5 kJ/mol
Heat of vaporization 113 kJ/mol
Vapor pressure
P/Pa 1 10 100 1 k 10 k 100 k
at T/K 819 906 1037 1209 1446 1799
Atomic properties
Crystal structure cubic body centered
Oxidation states 2
(strongly basic oxide)
Electronegativity 0.9 (Pauling scale)
Ionization energies 1st: 509.3 kJ/mol
2nd: 979.0 kJ/mol
Atomic radius 215 pm
Miscellaneous
Magnetic ordering nonmagnetic
Electrical resistivity (20 °C) 1 µΩ·m
Thermal conductivity (300 K) 18.6 W/(m·K)
CAS registry number 7440-14-4
Notable isotopes
Main article: Isotopes of radium
iso NA half-life DM DE (MeV) DP
223Ra ? 11.43 d alpha 5.99 219Rn
224Ra ? 3.6319 d alpha 5.789 220Rn
226Ra trace 1602 y alpha 4.871 222Rn
228Ra syn 6.7 y beta- 0.046 228Ac

Radium (chemical symbol Ra, atomic number 88) is an extremely radioactive element that is classified as an an alkaline earth metal. When freshly prepared, the pure metal is brilliant white, but it blackens when exposed to air. It is found in trace amounts in uranium ores. Its most stable isotope, Ra-226, has a half-life of 1,602 years and decays into radon gas.

Occurrence

Radium is a decay product of uranium and is therefore found in all uranium-bearing ores. It was originally acquired from pitchblende ore from Joachimsthal, Bohemia. (Seven metric tons of pitchblende yielded one gram of radium.) Some of this element can be obtained from the carnotite sands of Colorado, but there are richer ores in the Democratic Republic of the Congo and the Great Lakes area of Canada. It can also be extracted from uranium processing waste. Large uranium deposits are located in Ontario (Canada), New Mexico and Utah (United States), Australia, and other parts of the world.

History

Radium (from the Latin word radius, meaning "ray") was discovered by Maria Skłodowska-Curie and her husband Pierre in 1898. The Curies were studying pitchblende, a variety of the uranium ore uraninite (mainly uranium dioxide, UO2) obtained from North Bohemia (area around Jáchymov). When they removed uranium from the ore, they found that the remaining material was still radioactive. They then separated out a radioactive mixture, consisting mostly of barium, which gave a brilliant red flame color and spectral lines that had never been documented before.

In 1902, Marie Curie and Andre Debierne isolated radium in its pure metallic form. Their method involved electrolysis of a solution of pure radium chloride, using a mercury cathode, and distillation the product in an atmosphere of hydrogen gas.

Historically, the radioactive decay products of radium were labeled Radium A, B, C, and so forth (see Radioactivity below). These are now recognized as isotopes of other elements. On February 4, 1936, radium E became the first radioactive element to be made synthetically.

During the 1930s, it was found that workers exposed to radium when handling luminescent paints suffered from serious health problems, including sores, anemia, and bone cancer. This use of radium was stopped soon afterward. The reason for this problem is that the body treats radium as though it were calcium. Thus, radium becomes deposited in the bones, where radioactivity degrades the marrow and damages bone cells. Marie Curie's premature death has been attributed to her extensive work with radium.

Notable characteristics

Radium is the heaviest of the alkaline earth metals. It lies directly below barium in group 2 (former group 2A) of the periodic table, and its chemical properties therefore most closely resemble those of barium. In addition, it is placed in period 7, between francium and actinium.

Radium is intensely radioactive, emitting three types of radiation: alpha particles, beta particles, and gamma rays. When mixed with beryllium, radium produces neutrons. Another remarkable property of radium preparations is that they keep themselves warmer than their surroundings.

Radium is luminescent, giving a faint blue color, and is slightly more volatile than barium. Like other alkaline earth metals, it reacts with water to form the hydroxide, which is alkaline.

Isotopes

Radium has 25 known isotopes, four of which—Ra-223, Ra-224, Ra-226, and Ra-228—are are found in nature and are generated by the decay of uranium or thorium. The common isotope is Ra-226, a product of U-238 decay. It is the longest-lived isotope of radium, with a half-life of 1,602 years. The next longest-lived isotope is Ra-228, a product of Th-232 breakdown, with a half-life of 6.7 years.

Radioactivity

Radium is over one million times more radioactive than the same mass of uranium. It loses about 1% of its activity in 25 years, being transformed into elements of lower atomic weight. The final product of disintegration is lead.

The decay of radium occurs in stages. The successive main products were called radium emanation (or exradio), radium A, radium B, radium C, and so forth. These products have been studied and are now known to be isotopes of other elements, as follows.

Radium emanation: radon-222
Radium A: polonium-218
Radium B: lead-214
Radium C: bismuth-214
Radium C1: polonium-214
Radium C2: thallium-210
Radium D: lead-210
Radium E: bismuth-210
Radium F: polonium-210

The SI unit of radioactivity is the becquerel (Bq), corresponding to one disintegration per second. The curie, a non-SI unit, is defined as the amount of radioactivity that has the same disintegration rate as 1 gram of Ra-226 (3.7 x 1010 disintegrations per second, or 37 GBq).

Compounds

The compounds of radium color flames crimson carmine (rich red or crimson color with a shade of purple) and give characteristic spectra. Given that radium has a geologically short half-life and intense radioactivity, its compounds are quite rare, occurring almost exclusively in uranium ores. Some compounds of radium are its oxide (RaO), fluoride (RaF2), chloride (RaCl2), bromide (RaBr2), and iodide (RaI2).

Applications

Some of the practical uses of radium are derived from its radiative properties. More recently discovered radioisotopes, such as cobalt-60 and caesium-137, are replacing radium in even these limited uses because several of these are much more powerful and others are safer to handle.

  • Formerly used in self-luminous paints for watches, clocks and instrument dials. More than 100 former watch dial painters who used their lips to shape the paintbrush died from the radiation. (See Radium Girls). Soon afterward, the adverse effects of radioactivity became widely known. Radium was still used in dials as late as the 1950's. Objects painted with this paint may still be dangerous, and must be handled properly. Currently, tritium is used instead of radium. Although tritium still carries some risks, it is considered by many to be safer than radium.
  • When mixed with Beryllium it is a neutron source for physics experiments.
  • Radium (usually in the form of radium chloride) is used in medicine to produce radon gas which in turn is used as a cancer treatment.
  • Radium-223 is currently under investigation for use in medicine as cancer treatment of bone metastasis.
  • One unit for radioactivity, the non-SI curie, is based on the radioactivity of radium-226 (see Radioactivity).
  • At the turn of the 20th century radium was a popular additive in products like toothpaste, hair creams, and even food items due to its supposed curative powers. Such products soon fell out of vogue, and were prohibited by authorities in many countries, after it was discovered they could have real and serious adverse health effects. (See for instance Radithor.)
  • Spas featuring radium-rich water are still occasionally touted as beneficial, such as those in Misasa, Tottori, Japan.

Precautions

Radium is highly radioactive and its decay product, radon gas is also radioactive. Since radium is chemically similar to calcium, it has the potential to cause great harm by replacing it in the bone. Inhalation, injection, ingestion or body exposure to radium can cause cancer and other body disorders. Stored radium should be ventilated to prevent accumulation of radon.

Emitted energy from the decay of radium ionizes gases, affects photographic plates, causes sores on the skin, and produces many other detrimental effects.

Further reading

  • Scientific American (Macklis RM, The great radium scandal. Sci.Am. 1993 Aug: 269(2):94-99)
  • Clark, Claudia. (1987). Radium Girls: Women and Industrial Health Reform, 1910-1935. University of North Carolina Press. ISBN 0-8078-4640-6.
  • Ken Silverstein, Harper's Magazine, November 1998; The radioactive boy scout: when a teenager attempts to build a breeder reactor - case of David Hahn who managed to secure materials and equipment from businesses and information from government officials to develop an atomic energy radiation project for his Boy Scout merit-badge.
  • Decay chains (with some examples including Radium)

References
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External links

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