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Radium

Physics & Chemistry:

Radium

Radium electroplated over copper. Source: Creative Commons Radium electroplated over copper. Source: Creative Commons
Published:
Updated: June 24, 2012, 9:55 pm
Topics: Periodic Table Physics & Chemistry Human Health
This article has been reviewed by the following Topic Editor: C Michael Hogan
This article is written at a definitional level only. Authors wishing to expand this entry are inivited to expand the present treatment, which additions will be peer reviewed prior to publication of any expansion.

Radium is a the chemical element having atomic number 88, known by the atomic symbol Ra. Radium is a virtually pure-white alkaline earth metal that readily oxidises upon exposure to the atmosphere, thence becoming black in colour. Every isotope of radium is radioactive, the most stable isotope being radium-226, with a halflife of approximately 1601 years; moreover, this isotope decays to radon, which is, in turn, a radioactive gas. Due to its instability, radium exhibits luminescence, presenting a ing a faint blue glow.

Previous Element: Francium

Next Element: Actinium
88

Ra

226.03
Physical Properties
Color white
Phase at Room Temp. solid
Density (g/cm3) 5.5
Hardness (Mohs) ---
Melting Point (K) 973.2
Boiling Point (K) 1973
Heat of Fusion (kJ/mol) 8.5
Heat of Vaporization (kJ/mol) 113
Heat of Atomization (kJ/mol) 159
Thermal Conductivity (J/m sec K) 18.6
Electrical Conductivity (1/mohm cm) ---
Source pitchblende (U-238 decay)
Atomic Properties
Electron Configuration [Rn]7s2
Number of Isotopes 37(4 natural)
Electron Affinity (kJ/mol) ---
First Ionization Energy (kJ/mol) 509.4
Second Ionization Energy (kJ/mol) 979.1
Third Ionization Energy (kJ/mol) ---
Electronegativity 0.9
Polarizability (Å3) 38.3
Atomic Weight 226.03
Atomic Volume (cm3/mol) 41.1
Ionic Radius2- (pm) ---
Ionic Radius1- (pm) ---
Atomic Radius (pm) ---
Ionic Radius1+ (pm) ---
Ionic Radius2+ (pm) 162
Ionic Radius3+ (pm) ---
Common Oxidation Numbers +2
Other Oxid. Numbers ---
Abundance
In Earth's Crust (mg/kg) 9.0×10-7
In Earth's Ocean (mg/L) 8.9×10-11
In Human Body (%) 0.00%
Regulatory / Health
CAS Number 7440-14-4
OSHA Permissible Exposure Limit (PEL) No limit
OSHA PEL Vacated 1989 No limit
NIOSH Recommended Exposure Limit No limit
Sources:
Mineral Information Institute
Jefferson Accelerator Laboratory
EnvironmentalChemistry.com		  

References

Citation

Mineral Information Institute (Lead Author);Adam Sibley (Contributing Author);C Michael Hogan (Topic Editor) "Radium". In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth October 20, 2006; Last revised Date June 24, 2012; Retrieved May 25, 2013 <http://www.eoearth.org/article/Radium?topic=49557>

The Author

Mineral Information Institute The Mineral Information Institute (MII) is a national 501 (c)(3) not-for-profit organization dedicated to educating youth about the science of minerals and other natural resources, and about their importance in our every day lives. Each year MII works with interested professional and scientific associations, and various government and education agencies, to help classroom teachers develop materials that are directly usable by teachers in a variety of subjects and a multitude of grade levels. Al ... (Full Bio)

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