Quick Facts
| Property | Value |
|---|---|
| Symbol | Pm |
| Atomic Number | 61 |
| Atomic Mass | [145] u |
| Category | Lanthanide |
| Period | 6 |
| Group | 3 |
| Block | f |
| Electron Configuration | [Xe] 4f⁵ 6s² |
Physical Properties
| Property | Value |
|---|---|
| State at 20°C | Solid |
| Density | 7.26 g/cm³ |
| Melting Point | 1042°C (1315 K) |
| Boiling Point | 3000°C (3273 K) |
| Appearance | Metallic (predicted) |
History and Discovery
Discovered by: Charles D. Coryell, Jacob A. Marinsky, Lawrence E. Glendenin Year of Discovery: 1945 Location: Oak Ridge, Tennessee, USA
Etymology
Named after Prometheus, the Greek Titan who stole fire from the gods for humanity.
Discovery Story
Promethium was produced in 1945 from uranium fission products at Oak Ridge National Laboratory. It was the last lanthanide element to be discovered and the only one with no stable isotopes.
Isotopes
All isotopes are radioactive. The most stable is Pm-145 with a half-life of 17.7 years.
Applications and Uses
- Nuclear batteries (promethium-147)
- Luminous paint (historical)
- Thickness gauges
- Research applications
Interesting Facts
- Promethium is the only lanthanide with no stable isotopes
- It was predicted by Henry Moseley in 1914 and searched for until 1945
- Named after the myth of Prometheus bringing fire to humans
- Exists on Earth only in trace amounts from uranium decay
- About 500 grams of Pm exist in Earth's crust at any time