Radium
From The Encyclopedia of Earth
Radium electroplated over copper. Source: Creative Commons
| 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 (Earth's 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 |
| |
| 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: |
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References
- Curie, Marie and Debierne, André (1910). "Sur le radium métallique" (On metallic radium)" (in French). Comptes Rendus 151: 523–525. Retrieved 2009-08-01.
- Livingood (b. 1903), collaborated with Glenn T. Seaborg for five years, including 1936–8 at U.C. Berkeley. Tapscott, E. (1998). "Explorer of the Mysteries of the Atom". Journal of nuclear medicine: official publication, Society of Nuclear Medicine 39 (6): 16N–17N. PMID9627318 (Radium).
- Livingood, J. (1936). "Deuteron-Induced Radioactivities". Phys Rev 50 (5): 425–434. Bibcode 1936PhRv...50..425L.
- Weeks, Mary Elvira (1933). "The discovery of the elements. XIX. The radioactive elements". Journal of Chemical Education 10 (2): 79.
