Radium

Francium - Radium - Actinium Ba Ra       Full table
General
Name, Symbol, Number	Radium, Ra, 88
Series	Alkali earth metals
Group, Period, Block	2(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]7s2
e- 's per energy level	2, 8, 18, 32, 18, 8, 2
Oxidation states (Oxide)	2 (strong base)
Crystal structure	Cubic body centered
Physical Properties
State of matter	solid (nonmagnetic)
Melting point	973 K (1292 °F)
Boiling point	2010 K (3159 °F)
Molar volume	41.09 ×10-3 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
iso NA half-life DM DE MeV DP 226Ra trace 1602 y alpha 4.871 222Rn 228Ra {syn.} 6.7 y beta- 0.046 228Ac
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 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, decomposes in water and is a bit more volatile than barium.

Applications The only 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.

• One gram of radium yields ~0.0001 ml of radon gas each day which is used in cancer and other treatments.
• Formerly used in self-luminous paints for watch, clock and instrument dials.
• Neutron source for high energy physics experiments.

History Radium (Latin radius, ray) was discovered by Marie Curie in 1898 in pitchblende/uraninite from North Bohemia. In 1911 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.

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 Curie's premature death.

Occurrence 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^-* --> ½Cl₂ (gas|g) + e^-

Compounds Its compounds (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.

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.

External Links

• WebElements.com - Radium (http://www.webelements.com/webelements/elements/text/Ra/index)
• EnvironmentalChemistry.com - Radium (http://environmentalchemistry.com/yogi/periodic/Ra)

Lateral Science - Radium Discovery (http://www.lateralscience.co.uk/radium/RaDisc)