Promethium (Pm): electron configuration, atomic mass and facts
Promethium (Pm) is element 61 of the periodic table, a lanthanide in period 6 (f-block). Its electron configuration is [Xe] 4f5 6s2, with electrons arranged in shells 2, 8, 18, 23, 8, 2, and its most stable isotope has mass number 145.
▶ Watch Promethium’s electrons orbit in the interactive periodic tablePromethium at a glance
| Symbol | Pm |
|---|---|
| Atomic number | 61 |
| Atomic mass | [145] u (most stable isotope) |
| Category | Lanthanide |
| Group | f-block (no group number) |
| Period | 6 |
| Block | f-block |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f5 5s2 5p6 6s2 |
| Noble-gas shorthand | [Xe] 4f5 6s2 |
| Electrons per shell | 2, 8, 18, 23, 8, 2 |
| Electronegativity (Pauling) | 1.13 |
| State at 20 °C | solid |
Where is Promethium on the periodic table?
Promethium is in period 6 of the f-block, the lanthanide row printed below the main table. It has 6 electron shells, and this row is where the 4f subshell fills.
How to work out the electron configuration of Promethium
Put 61 electrons into subshells in order of rising energy, filling each before starting the next: 1s² (2), 2s² (4), 2p⁶ (10), 3s² (12), 3p⁶ (18), 4s² (20), 3d¹⁰ (30), 4p⁶ (36), 5s² (38), 4d¹⁰ (48), 5p⁶ (54), 6s² (56), 4f⁵ (61). In shorthand, [Xe] stands for the 54 electrons of xenon, giving [Xe] 4f⁵ 6s².
How electronegative is Promethium?
Promethium has a Pauling electronegativity of 1.13, ranking 83 of the 100 elements with a known value (fluorine is highest at 3.98). That is low: it tends to give up electrons and form positive ions.
Frequently asked questions
What is the electron configuration of Promethium?
The electron configuration of Promethium (Pm) is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f5 5s2 5p6 6s2. In noble-gas shorthand it is written [Xe] 4f5 6s2.
How many electrons does Promethium have in each shell?
Promethium has 61 electrons arranged in shells as 2, 8, 18, 23, 8, 2.
What is the atomic mass of Promethium?
Promethium has no stable isotopes. Its most stable isotope has a mass number of 145.
Is Promethium a metal?
Yes. Promethium is a lanthanide.
Explore nearby elements
More lanthanides: Cerium, Praseodymium, Neodymium, Samarium, Europium, Gadolinium. See all elements on the periodic table.