Radium
Element 88 · Alkaline Earth Metal
Radium is the heaviest alkaline earth metal and one of the most radioactive naturally occurring elements. Freshly prepared radium metal is nearly white, but it darkens in air as it reacts. It decays through a chain of radioactive daughters, releasing alpha particles, and glows faintly in the dark from radioluminescence. Historically it was painted onto watch dials; today its use is limited to specialized medical therapy because of the serious radiation hazard.
Key facts
| Atomic number | 88 |
|---|---|
| Atomic weight | [226] |
| Category | Alkaline Earth Metal |
| Group / Period | 2 / 7 |
| Block | s |
| Electron configuration | [Rn] 7s2 |
| Common oxidation states | +2 |
| State at STP | Solid |
| Electronegativity | 0.9 |
| Density | 5.5 g/cm3 |
| Melting point | 700 °C |
| Boiling point | 1737 °C |
Occurrence
Radium is found in trace amounts in uranium ores such as pitchblende, typically about one part per three million parts of uranium. It forms as a decay product of uranium-238 and is extracted from ore processing residues.
Applications
Radium-223 therapy for bone metastases in prostate cancer
Historical: luminous paint on dials and instruments (discontinued)
Industrial radiography sources (largely replaced by safer isotopes)
Common compounds
- Radium chloride (RaCl2)
- Radium sulfate (RaSO4)
- Radium bromide (RaBr2)
Radium was discovered in 1898 by Marie Sklodowska-Curie and Pierre Curie, who isolated it from tons of pitchblende residue.
Data source: IUPAC standard atomic weights 2021