Chemical element · Atomic number 61
Promethium
Promethium in the periodic table: atomic number 61, electron configuration, atomic mass, physical data, oxidation states, media credit and visible sources.
Lanthanide
solid
[144.91276] u
Generated illustrationGenerated illustration, Quanta Study. Not a photograph of a sample.
Generated illustration of Promethium; the image does not show a sample of the element.
Highly radioactive element; no freely licensed photograph of a sample is available.
Code-native illustration with the Quanta Study mark inside the image; not a photograph, no AI model involved.
Atomic classification
Shell occupancy
Promethium in the Bohr shell model
This shows the electron distribution of the neutral atom in a simplified shell model.
- K · n=1
- 2 electrons
- L · n=2
- 8 electrons
- M · n=3
- 18 electrons
- N · n=4
- 23 electrons
- O · n=5
- 8 electrons
- P · n=6
- 2 electrons
- Electron configuration
- [Xe]6s2 4f5
- Electrons per shell
- 2 · 8 · 18 · 23 · 8 · 2
- Group
- not reported
- Period
- 6
- Block
- F
- Element category
- Lanthanide
Physical and chemical properties
- Atomic mass
- [144.91276] u
- Standard state
- solid
- Density
- 7.26 g/cm³
- Melting point
- 1,315 K
- Boiling point
- 3,273 K
- Electronegativity
- not reported
- First ionisation energy
- 5.55 eV
- Oxidation states
- +3
- Discovery
- 1945
Safety and periodic classification
Safety
Safe handling cannot be inferred from Promethium's position in the periodic table alone. Laboratory, classroom and disposal decisions must follow the documentation for the exact material and its safety data sheet.
Position and comparison
Promethium is in period 6 and the F block. Its direct neighbours by atomic number are Neodymium and Samarium. The snapshot does not report a Pauling electronegativity. Periodic trends are compared only through the separately sourced neighbouring values.
Sources and scope
PubChem attributes element data to sources including IUPAC, NIST and IAEA. Quanta stores the referenced snapshot locally and leaves unknown values unavailable.
Where Promethium sits among the 118 elements
The table compares the reported values for Promethium with every other element that carries the same value in the snapshot. A rank is not a judgement, it is orientation: it says how unusual this value is across the periodic table.
| Value | Promethium | Position in the data set |
|---|---|---|
| Melting point | 1,315 K | Rank 47 of 103 elements with a reported value. Highest: Carbon. |
| Boiling point | 3,273 K | Rank 33 of 93 elements with a reported value. Highest: Rhenium. |
| Density | 7.26 g/cm³ | Rank 46 of 96 elements with a reported value. Highest: Osmium. |
| Ionisation energy | 5.55 eV | Rank 89 of 102 elements with a reported value. Highest: Helium. |
All values and ranks come from the PubChem Periodic Table snapshot, retrieved on 2026-07-15. Elements without a reported value are excluded, so the population differs per row.
The neighbours of Promethium in the periodic table
- Place in the table
- No group number, period 6, F block. Classified as lanthanide, solid at standard conditions.
- Direct neighbours
- Atomic number 61. Preceded by Neodymium, followed by Samarium.
- Discovery
- Recorded in the snapshot as: 1945. Who, where and under what circumstances is not part of that record, so this page carries the sourced year and no discovery narrative.
- Oxidation states
- +3. They follow from the electron configuration [Xe]6s2 4f5 and indicate which compounds to expect.
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