Listing description
Radium is a radioactive chemical element which has the symbol Ra and atomic number 88. Its appearance is almost pure
white, but it readily oxidizes on exposure to air, turning black.
Radium is an alkaline
earth metal
that is found in trace amounts in uranium ores. Its most stable isotope, 226Ra, has a half-life of 1601 years and decays into radon gas.
Detailed dscription
The
heaviest of the alkaline earth metals,
radium is intensely radioactive and resembles barium
in its chemical behavior. This metal is found in tiny quantities in the uranium
ore pitchblende,
and various other uranium minerals. Radium
preparations are remarkable for maintaining themselves at a higher temperature
than their surroundings, and for their radiations, which are of three kinds: alpha
particles, beta particles,
and gamma
rays.When freshly prepared, pure radium metal is brilliant white, but blackens when exposed to air (probably due to nitride formation). Radium is luminescent (giving a faint blue color), reacts violently with water and oil to form radium hydroxide and is slightly more volatile than barium. The normal phase of radium is a solid.
Applications
Some
of the few practical uses of radium are derived from its radioactive
properties. More recently discovered radioisotopes,
such as 60Co
and 137Cs,
are replacing radium in even these limited uses because several of these
isotopes are more powerful emitters, safer to handle, and available in more
concentrated form.When mixed with beryllium it is a neutron source for physics experiments.
Historical uses
Radium
was formerly used in self-luminous
paints for watches, nuclear panels, aircraft switches, clocks, and instrument
dials. In the mid-1920s, a lawsuit was filed by five dying "Radium
Girl" dial painters who had painted radium-based luminous
paints on the dials of watches and clocks. The dial painters' exposure
to radium caused serious health effects which included sores, anemia
and bone cancer. This is
because radium is treated as calcium
by the body, and deposited in the bones,
where radioactivity degrades marrow
and can mutate bone cells.During the litigation, it was determined that company scientists and management had taken considerable precautions to protect themselves from the effects of radiation, yet had not seen fit to protect their employees. Worse, for several years, the companies had attempted to cover up the effects and avoid liability by insisting that the Radium Girls were instead suffering from syphilis. This complete disregard for employee welfare had a significant impact on the formulation of occupational disease labor law.[1]
As a result of the lawsuit, the adverse effects of radioactivity became widely known, and radium dial painters were instructed in proper safety precautions and provided with protective gear. In particular, dial painters no longer shaped paint brushes by lip. Radium was still used in dials as late as the 1960s, but there were no further injuries to dial painters. This further highlighted that the plight of the Radium Girls was completely preventable.
After the 1960s, radium paint was first replaced with promethium paint, and later by tritium bottles which continue to be used today. Although the beta radiation from tritium is potentially dangerous if ingested, it has replaced radium in these applications.
Radium was also put in some foods for taste and as a preservative, but also exposed many people to radiation.[citation needed] Radium was once an additive in products like toothpaste, hair creams, and even food items due to its supposed curative powers.[2] Such products soon fell out of vogue and were prohibited by authorities in many countries, after it was discovered they could have 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. In the U.S., nasal radium irradiation was also administered to children to prevent middle ear problems or enlarged tonsils from the late 1940s through early 1970s.[3]
In 1909, the famous Rutherford experiment used radium as an alpha source to probe the atomic structure of gold. This experiment led to the Rutherford model of the atom and revolutionized the field of nuclear physics.
Radium (usually in the form of radium chloride) was used in medicine to produce radon gas which in turn is used as a cancer treatment, for example several of these radon sources were used in Canada in the 1920s and 1930s.[4] The isotope 223Ra is currently under investigation for use in medicine as cancer treatment of bone metastasis.
History
Radium
(Latin radius,
ray) was discovered
by Marie Skłodowska-Curie
and her husband Pierre in 1898 in pitchblende
coming from North Bohemia, in the Czech Republic (area
around Jáchymov). While
studying pitchblende the Curies removed uranium from it and found that the
remaining material was still radioactive. They then separated out a radioactive
mixture consisting mostly of barium
which gave a brilliant green flame color and crimson
carmine spectral lines
which had never been documented before. The Curies announced their discovery to
the French Academy of Sciences
on 26 December 1898.[5]In 1910, radium was isolated as a pure metal by Curie and André-Louis Debierne through the electrolysis of a pure radium chloride solution by using a mercury cathode and distilling in an atmosphere of hydrogen gas.[6]
Radium was first industrially produced in the beginning of the 20th Century by Biraco, a subsidiary company of Union Minière du Haut Katanga (UMHK) in its Olen plant in Belgium. UMHK offered to Marie Curie her first gramme of radium.
Historically the decay products of radium were known as radium A, B, C, etc. These are now known to be isotopes of other elements as follows:
|
Isotope
|
|
|
Radium emanation
|
|
|
Radium A
|
|
|
Radium B
|
|
|
Radium C
|
|
|
Radium C1
|
214Po
|
|
Radium C2
|
|
|
Radium D
|
210Pb
|
|
Radium E
|
210Bi
|
|
Radium F
|
One unit for radioactivity, the non-SI curie, is based on the radioactivity of 226Ra (see Radioactivity).
Occurrence
Radium
is a decay product
of uranium and is therefore found in all uranium-bearing ores.
(One ton
of pitchblende
typically yields about one seventh of a gram
of radium).[10]
Radium was originally acquired from pitchblende ore from Joachimsthal,
Bohemia, in the Czech Republic. Carnotite
sands in Colorado
provide some of the element, but richer ores are found in the Democratic Republic of the Congo
and the Great Lakes
area of Canada,
and can also be extracted from uranium processing waste. Large
radium-containing uranium deposits are located in Canada (Ontario),
the United States (New Mexico, Utah,
and Virginia),
Australia,
and in other places.Uranium (pronounced /jʊˈreɪniəm/ yoo-RAY-nee-əm) is a silvery-white metallic chemical element in the actinide series of the periodic table with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. The uranium nucleus binds between 141 and 146 neutrons, establishing six isotopes, the most common of which are U-238 (146 neutrons) and U-235 (143 neutrons). All isotopes are unstable and uranium is weakly radioactive. Uranium has the second highest atomic weight of the naturally occurring elements, lighter only than plutonium-244.[3] Its density is about 70% higher than that of lead, but not as dense as gold or tungsten. It occurs naturally in low concentrations of a few parts per million in soil, rock and water, and is commercially extracted from uranium-bearing minerals such as uraninite.
In nature, uranium is found as uranium-238 (99.284%), uranium-235 (0.711%),[4] and a very small amount of uranium-234 (0.0058%). Uranium decays slowly by emitting an alpha particle. The half-life of uranium-238 is about 4.47 billion years and that of uranium-235 is 704 million years,[5] making them useful in dating the age of the Earth.
Many contemporary uses of uranium exploit its unique nuclear properties. Uranium-235 has the distinction of being the only naturally occurring fissile isotope. Uranium-238 is fissionable by fast neutrons, and is fertile, meaning it can be transmuted to fissile plutonium-239 in a nuclear reactor. Another fissile isotope, uranium-233, can be produced from natural thorium and is also important in nuclear technology. While uranium-238 has a small probability for spontaneous fission or even induced fission with fast neutrons, uranium-235 and to a lesser degree uranium-233 have a much higher fission cross-section for slow neutrons. In sufficient concentration, these isotopes maintain a sustained nuclear chain reaction. This generates the heat in nuclear power reactors, and produces the fissile material for nuclear weapons. Depleted uranium (U-238) is used in kinetic energy penetrators and armor plating.[6]
Uranium is used as a colorant in uranium glass, producing orange-red to lemon yellow hues. It was also used for tinting and shading in early photography. The 1789 discovery of uranium in the mineral pitchblende is credited to Martin Heinrich Klaproth, who named the new element after the planet Uranus. Eugène-Melchior Péligot was the first person to isolate the metal and its radioactive properties were uncovered in 1896 by Antoine Becquerel.
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