Promethium (Pm) – element 61
Promethium is a chemical element with the symbol Pm and atomic number 61. It is a lanthanide in group 3 (lanthanides), period 6 of the periodic table (f-block), and is a solid at room temperature.
Promethium (Pm) has atomic number 61, atomic mass [145] and electron configuration [Xe] 4f5 6s2.
Promethium facts
| Symbol | Pm |
|---|---|
| Atomic number | 61 |
| Atomic mass | [145] |
| Category | lanthanide |
| Group | group 3 (lanthanides) |
| Period | 6 |
| Block | f-block |
| Phase at 20 °C | Solid |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f5 |
| Noble-gas notation | [Xe] 4f5 6s2 |
| Electrons per shell | 2, 8, 18, 23, 8, 2 |
Bohr model and shells
Promethium has 61 electrons in 6 shells: 2, 8, 18, 23, 8, 2. Full configuration and noble-gas notation are in the table; work out any element or ion with the electron configuration calculator.
Physical and atomic properties
| Melting point | 1315 K (1041.8 °C) |
|---|---|
| Boiling point | 3273 K (2999.8 °C) |
| Density | 7.26 g/cm³ |
| Electronegativity (Pauling) | 1.13 |
| Electron affinity | 12.45 kJ/mol |
| Ionization energies | 540, 1050, 2150 kJ/mol (1st, 2nd, 3rd) |
| Discovered by | Chien Shiung Wu |
Use the atomic mass in the molar mass calculator for any formula containing Pm.
Position in the periodic table
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Frequently asked questions
What is the atomic mass of promethium?
The atomic mass of promethium is [145] (mass number of its longest-lived isotope, since it has no stable isotope).
What is the electron configuration of promethium?
Promethium has 61 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f⁵, or [Xe] 4f⁵ 6s² in noble-gas notation. Electrons per shell: 2, 8, 18, 23, 8, 2.
Is promethium a metal?
Yes. Promethium is a lanthanide.
Where is promethium on the periodic table?
Promethium is in group 3 (lanthanides), period 6, in the f-block.
Data: Periodic-Table-JSON (CC BY-SA 3.0); standard atomic weights from IUPAC (abridged). Values in brackets are the mass number of the longest-lived isotope.