Promethium · Pm Promethium
has no stable isotopes and its applications are mainly limited to specific radioactive sources and research.
- atomic number / Atomic number
- 61
- atomic weight / Atomic mass
- 144.91276 u
- Family/Group
- Lanthanum series (independent line)
- Period · Block / Period · Block
- 6 · f
- Category / Category
- Lanthanide series · Lanthanide
- State / State
- solid state
- Electron configuration
- [Xe]6s2 4f5
- Oxidation states / Oxidation states
- +3
- Electronegativity / Electronegativity
- not included
- Density / Density
- 7.26 g/cm³
- Melting point / Melting point
- 1315 K
- Boiling point / Boiling point
- 3273 K
- Atomic radius / Atomic radius
- 236 pm（van der Waals）
- First ionization energy
- 5.55 eV
- Discovery year / Discovery
- 1945
attribute description and data source
properties taken from PubChem periodic table snapshot (2026-10-04). Atomic weights may be reference values or representative isotope masses and cannot be considered exact constants for all samples; density, phase transition points, and phase states depend on temperature, pressure, and allotropes. The solidification of helium requires pressure. Some properties of radioactive and superheavy elements are predicted values, and missing items are marked as not included. Please check the original source and experimental conditions for precise calculations.