61Pm144.91276
Promethium
Lanthanide
Solid at STP
Period 6Block FDiscovered 1945
[Xe]6s2 4f5
Promethium, originally prometheum, is a chemical element with the symbol Pm and atomic number 61. All of its isotopes are radioactive; it is one of only two such elements that are followed in the periodic table by elements with stable forms, a distinction shared with technetium. Chemically, promethium is a lanthanide, which forms salts when combined with other elements.
📖 Read more on Wikipedia →Atomic Properties
| Atomic Number | 61 |
| Atomic Mass | 144.91276 u |
| Electron Configuration | [Xe]6s2 4f5 |
| Oxidation States | +3 |
| Atomic Radius | 236 pm |
| Ionization Energy | 5.55 eV |
| Block | F |
Physical Properties
| Appearance | metallic |
| Standard State | Solid |
| Melting Point | 1315 K (1041.8 °C) |
| Boiling Point | 3273 K (2999.8 °C) |
| Density | 7.26 g/cm³ |
| CPK Color | #A3FFC7 |
Classification
| Category | Lanthanide |
| Group Block | Lanthanide |
| Period | 6 |
| Block | F |
Discovery
| Year Discovered | 1945 |
| Discovered By | Chien Shiung Wu |
| Named By | Isotopes of promethium |
| Electron Shells | 2, 8, 18, 23, 8, 2 |