Element 61
Promethium
Lanthanides
Promethium (Pm) is in the f-block of the periodic table — group 3, period 6.
Promethium, originally prometheum, is a chemical element with the symbol Pm and atomic number 61.
Key data
- Atomic number
- 61
- Atomic mass
- 145.000 u
- Group / Period
- 3 / 6
- Block
- f-block
- Phase at STP
- Solid
- Density
- 7.26 g/cm³
- Melting point
- 1041.8 °C
- Boiling point
- 2999.8 °C
- Electron configuration
- [Xe] 4f5 6s2
Periodic table block
Promethium is in the f-block (group 3, period 6). Elements land in the f-block when their highest-energy electrons fill an f subshell — these are the lanthanides and actinides shown beneath the main table.
New to this? Periodic table blocks explained: s, p, d, and f
Common uses
- •Glow-in-the-dark dials
- •Beta-radiation sources
- •Nuclear batteries
Discovery
Year: 1945
Discovered by: Chien Shiung Wu
Named by: Isotopes of promethium
Frequently asked questions
What is the atomic number of Promethium?
Promethium has atomic number 61. Its symbol is Pm and its atomic mass is 145 u.
What category of element is Promethium?
Promethium is classified as lanthanides. It sits in group 3, period 6 of the periodic table.
What block of the periodic table is Promethium in?
Promethium is in the f-block (group 3, period 6). Its highest-energy electrons occupy the f subshell — you can see this in its electron configuration, [Xe] 4f5 6s2.
What is Promethium used for?
Common uses of Promethium include: Glow-in-the-dark dials, Beta-radiation sources, Nuclear batteries.
When was Promethium discovered?
Promethium was discovered in 1945 by Chien Shiung Wu.
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