Plutonium
Element 94 · Actinide
Plutonium is a silvery metal that feels noticeably warm because its own radioactive decay generates heat. It has six solid phases at ambient pressure and is chemically complex, with four common oxidation states that can coexist in solution. Plutonium-239 is fissile and was used in nuclear weapons; plutonium-238 powers radioisotope generators on spacecraft like Voyager and Perseverance. It is extremely toxic if inhaled, and all work with it requires strict radiological controls.
Key facts
| Atomic number | 94 |
|---|---|
| Atomic weight | [244] |
| Category | Actinide |
| Group / Period | — / 7 |
| Block | f |
| Electron configuration | [Rn] 5f6 7s2 |
| Common oxidation states | +4, +6, +5, +3 |
| State at STP | Solid |
| Electronegativity | 1.28 |
| Density | 19.816 g/cm3 |
| Melting point | 639.4 °C |
| Boiling point | 3228 °C |
Occurrence
Plutonium is essentially synthetic, produced in reactors by neutron capture on uranium-238. Only minute traces occur naturally in uranium ores.
Applications
Plutonium-238 in radioisotope thermoelectric generators for spacecraft
Mixed-oxide (MOX) fuel for some nuclear reactors
Historical: fissile material in nuclear weapons
Common compounds
- Plutonium dioxide (PuO2)
- Plutonium hexafluoride (PuF6)
- Plutonium nitrate (Pu(NO3)4)
Plutonium was secretly discovered in 1940-41 by Glenn Seaborg's team at Berkeley; its existence was kept classified until after World War II.
Data source: IUPAC standard atomic weights 2021