Promethium (Pm)
Promethium (Pm) is element 61 of the periodic table, a lanthanide in period 6, in the f-block. It has no stable isotope and no standard atomic weight; 145 is the mass number of its longest-lived isotope. At room temperature it is a solid; it melts at 1041.85 °C and boils at 2999.85 °C.
| Atomic number | 61 |
|---|---|
| Symbol | Pm |
| Standard atomic weight | [145] (mass number of the longest-lived isotope) |
| Molar mass | [145] g/mol |
| Category | Lanthanide |
| Group | f-block (lanthanide series) |
| Period | 6 |
| Block | f-block |
| Electron configuration | [Xe] 6s2 4f5 |
| Oxidation states | +3 |
| Electronegativity (Pauling) | — |
| Atomic radius (van der Waals) | 236 pm |
| First ionisation energy | 5.55 eV (535.5 kJ/mol) |
| Electron affinity | — |
| State at room temperature | Solid |
| Melting point | 1315 K (1041.85 °C) |
| Boiling point | 3273 K (2999.85 °C) |
| Density | 7.26 g/cm³ |
| Discovered | 1945 |
Lanthanides
La · LanthanumCe · CeriumPr · PraseodymiumNd · NeodymiumSm · SamariumEu · EuropiumGd · GadoliniumTb · TerbiumDy · DysprosiumHo · HolmiumEr · ErbiumTm · ThuliumYb · Ytterbium
Calculate with Promethium
Atomic weight: IUPAC CIAAW — no standard atomic weight; mass number in brackets. Other properties: PubChem (U.S. National Library of Medicine, public domain). Values such as melting point and radius depend on how they were measured; check a data book for precise work.