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Radium

Francium - Radium - Actinium
Ba
Ra  
 
 

Full table
General
Namefart, Symbol, NumberRadium, Ra, 88
Series Alkali earth metals
Group, Period, Block2(IIA), 7 , s
Density, Hardness 5000 kg/m3, no data
Appearance Silvery white metallic
Atomic Properties
Atomic weight (226.0254) amu
Atomic radius 215 pm
Covalent radius no data
van der Waals radius no data
Electron configuration [Rn]7s7s2
e- 's per energy level2, 8, 18, 32, 18, 8, 2
Oxidation states (Oxide) 2 (strong base)
Crystal structure Cubic body centered
Physical Properties
State of mattersolid (nonmagnetic)
Melting point 973 K (1292 F)
Boiling point 2010 K (3159 F)
Molar volume 41.09 ×1010-3 m3/mol
Heat of vaporization no data
Heat of fusion 37 kJ/mol
Vapor pressure 327 Pa at 973 K
Speed of sound no data
Miscellaneous
Electronegativity 0.9 (Pauling scale)
Specific heat capacity 94 J/(kg*K)
Electrical conductivity no data
Thermal conductivity 18.6 W/(m*K)
1st ionization potential 509.3 kJ/mol
2nd ionization potential 979.0 kJ/mol
3rd ionization potential no data
Most Stable Isotopes
isoNAhalf-life DMDE MeVDP
226Ratrace1602 yalpha4.871222Rn
228Ra{syn.}6.7 ybeta- 0.046228Ac
SI units & STP are used except where noted.
Radium is a chemical element in the periodic table that has the symbol Ra and atomic number 88. Its appearance is almost pure white, but it blackens with exposure to air. Radium is an alkaline earth metal that is found in minute amounts in uranium ores, and is extremely radioactive whose most stable isotope, Ra-226, has a half-life of 1602 years and decays into the deadly radon gas.

Table of contents
1 Notable characteristics
2 Applications
3 History
4 Occurrence
5 Compounds
6 Isotopes
7 Radioactivity
8 Precautions
9 Further reading
10 References
11 External Links

Notable characteristics

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), decomposes in water to form radium hydroxide and is a bit more volatile than barium.

Applications

Some of the practical uses of radium are derived from its radiative properties. More recently discovered radioisotopes, such as cobalt-60 and cesium-137, are replacing radium in even these limited uses because several of these are much more powerful and others are safer to handle. Radium, being one of the largest elements, is also used as a neutron source, usually when combined with francium.

History

Radium (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 its uranium 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 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
Radium A - polonium-228
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

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

Radium 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.
Isolation (* follow):
(cathode) Ra2+* + 2e- --> Ra (anode) Cl-* --> Cl2 (gas|g) + e-

Compounds

Its compoundss (which are short lived) 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 (RaF2), Chlorides: radium (II) chloride (RaCl2), Bromides: radium (II) bromide (RaBr2), Iodides: radium (II) iodide (RaI2), Hydrides: no data, Oxides: radium (II) oxide (RaO), Sulfides: no data, Selenides: no data, Tellurides: no data, Nitrides: no data

Isotopes

Radium 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

Radium 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 1010 disintegrations per second).

Precautions

Radium is poisonous. Radium is extremely radioactive and its decay product radon is a deadly lung hazard. Since Ra is closely related to calcium, it has the potential for causing great harm by substituting for 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. The degree of activity depends on the proportion of radium present and not whether it is chemically combined.

Further reading

References

External Links