61145PmPromethium
Promethium (Pm) — element 61lanthanide · period 6
Promethium is a chemical element with the symbol Pm and atomic number 61. It is a lanthanide in period 6 of the periodic table (the f-block), with a standard atomic mass of 145 u. At room temperature (25 °C) promethium is a solid.
💡 Known for: Radioactive and extremely rare in nature; it has been used in luminous paint and nuclear batteries.
# Promethium properties
| Symbol | Pm |
|---|---|
| Atomic number | 61 |
| Atomic mass | 145 u |
| Category | lanthanide |
| Group | — (f-block, no group number) |
| Period | 6 |
| Block | f-block |
| Electron configuration | [Xe] 4f⁵ 6s² |
| Full configuration | 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f⁵ 5s² 5p⁶ 6s² |
| Electrons per shell | 2, 8, 18, 23, 8, 2 |
| Protons / electrons | 61 / 61 |
| State at 25 °C | solid |
| Melting point | 1315 K (1041.8 °C, 1907.3 °F) |
| Boiling point | 3273 K (2999.8 °C, 5431.7 °F) |
| Density | 7.26 g/cm³ |
| Electronegativity (Pauling) | 1.13 |
| First ionization energy | 5.582 eV |
| Atomic radius | 205 pm |
| Discovered | 1945 |
# Electron configuration of promethium
The electron configuration of promethium is [Xe] 4f⁵ 6s², written out in full as 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f⁵ 5s² 5p⁶ 6s². Its 61 electrons fill 6 shells as 2, 8, 18, 23, 8, 2, so the outermost shell holds 2 electrons.
# Related elements
NdNeodymiumprevious elementSmSamariumnext elementLaLanthanumlanthanideCeCeriumlanthanidePrPraseodymiumlanthanideEuEuropiumlanthanideGdGadoliniumlanthanideTbTerbiumlanthanideDyDysprosiumlanthanideHoHolmiumlanthanide
# Promethium FAQ
What is the atomic number of promethium?
The atomic number of promethium is 61: every promethium atom has 61 protons in its nucleus. Its symbol is Pm.
What is the atomic mass of promethium?
The standard atomic mass of promethium is 145 u.
What is the electron configuration of promethium?
Promethium's electron configuration is [Xe] 4f⁵ 6s² (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f⁵ 5s² 5p⁶ 6s²), with 2, 8, 18, 23, 8, 2 electrons per shell.
Is promethium a metal?
Yes. Promethium is a lanthanide, one of the metals.
What is the melting point of promethium?
Promethium melts at 1315 K (1041.8 °C, 1907.3 °F) and boils at 3273 K (2999.8 °C, 5431.7 °F).
What is promethium used for / known for?
Radioactive and extremely rare in nature; it has been used in luminous paint and nuclear batteries.