Radium
Category:Chemical elements
\n| \n\n |
\n\n| General |
\n\n| Name, Symbol, Number | Radium, Ra, 88 |
\n\n| Series | Alkali earth metals |
\n\n| Group, Period, Block | 2(IIA), 7 , s |
\n\n| Density, Hardness | 5000 kg/m3, no data |
\n\n| Appearance | Silvery white metallic |
\n\n| Atomic Properties |
\n \n| Atomic weight | (226.0254) amu |
\n\n| Atomic radius | 215 pm |
\n\n| Covalent radius | no data |
\n\n| van der Waals radius | no data |
\n\n| Electron configuration | [Rn]7s7s2 |
\n\n| e- 's per energy level | 2, 8, 18, 32, 18, 8, 2 |
\n\n| Oxidation states (Oxide) | 2 (strong base) |
\n\n| Crystal structure | Cubic body centered |
\n\n| Physical Properties |
\n| State of matter | solid (nonmagnetic) |
\n\n| Melting point | 973 K (1292 °F) |
\n\n| Boiling point | 2010 K (3159 °F) |
\n\n| Molar volume | 41.09 ×1010-6 m3/mol |
\n\n| Heat of vaporization | no data |
\n\n| Heat of fusion | 37 kJ/mol |
\n\n| Vapor pressure | 327 Pa at 973 K |
\n\n| Speed of sound | no data |
\n\n| Miscellaneous |
\n\n| Electronegativity | 0.9 (Pauling scale) |
\n\n| Specific heat capacity | 94 J/(kg*K) |
\n\n| Electrical conductivity | no data |
\n\n| Thermal conductivity | 18.6 W/(m*K) |
\n\n| 1st ionization potential | 509.3 kJ/mol |
\n\n| 2nd ionization potential | 979.0 kJ/mol |
\n\n| 3rd ionization potential | no data |
\n\n| Most Stable Isotopes |
\n\n| \n\n |
\n\n| SI units & STP are used except where noted. | \n
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Radium is a
chemical element in the
periodic table that has the symbol Ra and
atomic number 88.\nIts appearance is almost pure white, but it blackens on exposure to air. Radium is an
alkaline earth metal \nthat is found in trace amounts in
uranium ores. It is extremely
radioactive. Its most stable
isotope, Ra-226, has a
half-life of 1602 years and decays into
radon gas.
Notable characteristics
\nThe heaviest of the alkaline earth metals, radium is intensely radioactive and resembles barium chemically. This metal is found (combined) in minute 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 rays, beta rays, and gamma rays. Radium also produces neutrons when mixed with beryllium.
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), corrodes in water to form radium hydroxide and is a bit more volatile than barium.
Applications
\nSome 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.\n*Formerly used in self-luminous paints for watch, clock and instrument dials. This use was discontinued after the adverse affects of radioactivity were popularized. Objects painted with this paint may still be dangerous, and must be handled properly.\n*When mixed with Beryllium it is a Neutron source for physics experiments.\n*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. \n*The unit for radioactivity, the curie, is based on the radioactivity of radium-226 (see Radioactivity).
History
\nRadium (Latin radius, ray) was discovered by Marie Curie and her husband Pierre in 1898 in pitchblende/uraninite from North Bohemia. 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 mostly consisting of barium which gave a brilliant red flame color and spectral lines which had never been documented before. In 1902 radium was isolated into its pure metal by Curie and Andre Debierne through the electrolysis of a pure radium chloride solution by using a mercury cathode and distilling in an atmosphere of hydrogen gas.
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:
- Radium emanation - radon-222\n:Radium A - polonium-228\n:Radium B - lead-214\n:Radium C - bismuth-214\n:Radium C1 - polonium-214\n:Radium C2 - thallium-210\n:Radium D - lead-210\n:Radium E - bismuth-210\n: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 worker exposure to radium by handling
luminescent paints caused serious health effects which included sores,
anemia and bone cancer. This use of radium was stopped soon afterward. Handling of radium has since been blamed for Marie Curie's premature death.
Occurrence
\nRadium is a decay product of uranium and is therefore found in all uranium-bearing
ores. Radium was originally acquired from
pitchblende ore from Joachimsthal, Bohemia (7 metric tons of pitchblende yields 1
gram of radium).
Carnotite sands in
Colorado provide some of the element, but richer ores are found in the
Democratic Republic of the Congo, the
Great Lake area of
Canada and can also be extracted from uranium processing waste. Large uranium deposits are located in
Ontario,
New Mexico,
Utah,
Australia, and in other places.
\n
Compounds
\nIts compoundss color flames
crimson carmine (rich red or crimson color with a shade of purple) and give a characteristic
spectrum. Due to its very short
half life and intense radioactivity, radium compounds are quite rare, occurring almost exclusively in uranium ores.
Fluorides: radium (II) fluoride (Ra
F2),
Chlorides:
radium (II) chloride (Ra
Cl2), Bromides: radium (II) bromide (Ra
Br2), Iodides: radium (II) iodide (Ra
I2), Hydrides: no data,
Oxides: radium (II) oxide (Ra
O),
Sulfides: no data, Selenides: no data, Tellurides: no data, Nitrides: no data
Isotopes
\nRadium has 25 different isotopes, four of which are found in nature, with radium-226 being the most common and stable. Ra-223, Ra-224, Ra-226 and Ra-228 are all generated in the decay of either
U or
Th. Ra-226 is a product of U-238 decay, and is the longest-lived isotope of Ra 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.
Radioactivity
\nRadium is over 1 million times more radioactive than the same amount of uranium. Its decay occurs in at least seven stages; the successive main products have been studied and are called radium emanation or exradio, radium A, radium B, radium C, etc. (The emanation is a heavy gas, the later products are solids.) These products are regarded as unstable 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. The
curie is defined as that amount of radioactivity which has the same disintegration rate as 1 gram of Ra-226 (3.7 x 10
10 disintegrations per second).
Precautions
\nRadium is extremely radioactive and its decay product, radon is a radioactive gas. Since Ra is closely related to calcium, it has the potential to cause great harm by substituting it in
bone. Inhalation, injection, or body exposure to radium can cause cancer and other body disorders. Stored radium should be ventilated to prevent build-up of radon.
Emitted energy from the decay of radium ionizes gases, affects photographic plates, causes sores on the skin, and produces many other dramatic effects.
Further reading
\n*Scientific American (Macklis RM, The great radium scandal. Sci.Am. 1993 Aug: 269(2):94-99)
References
\n*Guide to the Elements - Revised Edition, Albert Stwertka, (Oxford University Press; 1998) ISBN 0-19-508083-1 \n*Los Alamos National Laboratory - Radium
External Links
\n*WebElements.com - Radium (also used as a reference)\n*
EnvironmentalChemistry.com - Radium (also used as a reference)\n*
Lateral Science - Radium Discovery
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