Pm
Promethium
Element 61 · 145.0 u
Promethium is the only radioactive lanthanide with no stable isotopes.
Physical Properties
| Atomic Mass | 145.0 u |
| Density | 7.26 g/cm³ |
| Melting Point | 1315.0 K |
| Boiling Point | 3273.0 K |
| Appearance | Metallic |
| State at Room Temp | Solid |
Chemical Properties
| Electronegativity | 1.13 (Pauling) |
| 1st Ionization Energy | 540.0 kJ/mol |
| Electron Affinity | 12.45 kJ/mol |
| Oxidation States | +2, +3 |
Atomic Properties
| Electron Configuration | [Xe] 4f5 6s2 |
| Atomic Radius | 183.0 pm |
| Covalent Radius | 199.0 pm |
| Van der Waals Radius | 236.0 pm |
Discovery
| Discovered By | Charles D. Coryell, Jacob A. Marinsky, Lawrence E. Glendenin |
| Discovery Year | 1945 |
| Location | Oak Ridge, Tennessee, USA |
| Named After | Prometheus, the Titan of Greek mythology |
About Promethium
Promethium is a radioactive rare earth metal first produced from uranium fission products in 1945. Trace amounts exist in nature from uranium decay. Promethium-147 emits beta radiation.
Uses & Applications
Nuclear batteries, luminous paint, thickness gauges, and beta radiation sources.
Fun Fact
Promethium is named after Prometheus, the Titan who stole fire -- fitting for an element discovered in nuclear reactions.
Isotopes
| Mass Number | Abundance | Half-Life | Stable |
| 145 | - | 17.7 years | No |
| 147 | - | 2.6234 years | No |
Electron Configuration
[Xe] 4f5 6s2