Promethium (Pm)
Promethium is element 61, a lanthanide in period 6 of the periodic table. At room temperature it is a solid.
Electron configuration [Xe] 4f5 6s2
Electrons per shell 2, 8, 18, 23, 8, 2
Promethium data
| Atomic number | 61 |
|---|---|
| Symbol | Pm |
| Atomic mass | [145] (mass number of the longest-lived isotope) |
| Category | Lanthanide |
| Group | — (f-block) |
| Period | 6 |
| Block | f |
| State at 25 °C | solid |
| Melting point | 1373 K (1099.9 °C) |
| Boiling point | 3273 K (2999.9 °C) |
| Density | 7.264 g/cm³ |
| Electronegativity (Pauling) | 1.13 |
| Atomic radius | — |
| 1st ionization energy | 540 kJ/mol |
| Electron affinity | -50 kJ/mol |
| Oxidation states | +3 |
| Common ion charge | 3+ |
| Discovered | 1947 |
Orbital diagram
Each box is one orbital holding up to two electrons of opposite spin. Following Hund’s rule, electrons spread out singly across a subshell before pairing.
Work through promethium’s configuration and its ions →
Where promethium sits
Promethium belongs to the lanthanides. Its Pauling electronegativity of 1.13 is mid-range; see the electronegativity chart and periodic trends for context. To use its mass in a calculation, try the molar mass calculator.
Promethium FAQ
What is the electron configuration of promethium?
Promethium (Z = 61) has the configuration 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f5 6s2. In noble-gas shorthand that is [Xe] 4f5 6s2.
How many valence electrons does promethium have?
2 (2 in the outer s subshell).
What is the atomic mass of promethium?
Promethium has no stable isotopes. Its most stable known isotope has mass number 145, so tables list [145].
Is promethium a metal?
Yes. Promethium is a lanthanide.
What is the charge of a promethium ion?
Promethium most commonly forms Pm3+.