Promethium
lanthanide · period 6 · group 3 · f-block
Promethium is a chemical element with the symbol Pm and atomic number 61. All of its isotopes are radioactive; it is extremely rare, with only about 500–600 grams naturally occurring in Earth's crust at any given time.
What the numbers say
At standard temperature and pressure Promethium is a solid, sitting in period 6, group 3 of the f-block.
Its melting point of 1315 K (1042 °C) is the 47th highest of the 110 elements with a measured value — mid-range among the elements.
At 7.264 g/cm³ it is the 47th densest of 96 elements with a quoted density.
Pauling electronegativity is 1.13. Paired with oxygen (3.44) that is a difference of 2.31, which puts the bond predominantly ionic — expect a stable oxide ceramic.
First identified in 1945.
Check it against computed structures
The structure search queries the Materials Project, OQMD and the Open Materials Database for computed crystal structures containing Pm — with DFT formation energy, hull stability and band gap where the provider publishes them.
K 2 · L 8 · M 18 · N 23 · O 8 · P 2
Properties
| Atomic number | 61 |
|---|---|
| Atomic mass | 145 u |
| Series | lanthanide |
| Group | 3 |
| Period | 6 |
| Block | f-block |
| Phase at STP | Solid |
| Density | 7.264 g/cm³ |
| Melting point | 1315 K (1042 °C) |
| Boiling point | 3273 K (3000 °C) |
| Electronegativity (Pauling) | 1.13 |
| Electron configuration | [Xe] 4f⁵ 6s² |
| Oxidation states | 3 |
| Discovered | 1945 |
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See Pm in context with all 118 elements.
Working with promethium in a real design?
Ask the materials chat how Pm behaves in your alloy system, what it does to weldability, and which grades to look at — with the source of every number named.