Atomic Properties of Pu
- Atomic Number of Pu
- 94
- Atomic Mass of Pu
- 244.0000 u
- Electron Configuration
- [Rn] 5f6 7s2
- Electronegativity
- 1.28
- Block
- f-block
- Group
- —
- Period
- 7
Glenn Seaborg, Edwin McMillan, Joseph Kennedy, and Arthur Wahl produced and identified plutonium at Berkeley in 1940 and 1941. They named it after Pluto, continuing the uranium-Neptune sequence. Wartime secrecy delayed public announcement while plutonium production became part of the Manhattan Project and the weapon used on Nagasaki.
Isotope identity changes the story. Plutonium-239 is fissile and has been used in nuclear weapons and reactor fuel. Plutonium-238 has a much shorter half-life and releases steady decay heat; sealed radioisotope thermoelectric generators convert that heat into electricity for space probes quietly exploring regions where sunlight is weak. An RTG is not a fission reactor, and Pu-238 is selected for heat production rather than a chain reaction.
Plutonium metal has multiple solid phases and difficult physical behavior, while its compounds support several oxidation states. It is radiotoxic, especially when material enters the body, and some isotopes pose criticality concerns in sufficient configurations. Facilities therefore rely on containment, material accounting, shielding suited to associated radiation, and strict handling rules. A file cabinet of rules is only the paperwork edge of an engineered safety system.
Some plutonium can be recycled as mixed-oxide reactor fuel; other inventories require long-term secure management.
This Corebound paradox becomes clearer when the isotopes are named. Pu-239 connects fission energy and weapons history. Pu-238 powers long-duration instruments through decay heat. Both require stewardship extending far beyond the moment useful energy is released.