Pm
Promethium
Atomic number: 61Mass: 145 uCategory: Lanthanide
About Promethium
Promethium is an extremely rare radioactive rare-earth element. All isotopes are radioactive. It does not occur naturally on Earth in significant amounts and must be made artificially. It was the last naturally occurring element to be discovered.
Properties
Period
6
Group
N/A
Block
F
Category
Lanthanide
Electronegativity
1.13 (Pauling)
Ionization Energy
540 kJ/mol
Melting Point
1315 K (1042°C)
Boiling Point
3273 K (3000°C)
Density
7.26 g/cm³
Oxidation States
+3
Electron Configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f⁵ 5s² 5p⁶ 6s²
[Xe] 4f⁵ 6s²
Shell 1:2e⁻
Shell 2:8e⁻
Shell 3:18e⁻
Shell 4:23e⁻
Shell 5:8e⁻
Shell 6:2e⁻
Real-World Uses
Nuclear batteries (pacemakers)
Luminescent paint
Thickness gauges
X-ray sources
Research
Fun Fact
Promethium is so rare that only about 500 grams exist on Earth at any one time — all of it artificially made in nuclear reactors!