Plutonium
Plutonium (Pu) is element 94, an actinide in period 7 of the f-block. The mass of its longest-lived isotope is 244.0642 u. It is a solid at room temperature and melts at 639.85 °C. Its electron configuration is [Rn] 7s² 5f⁶.
Plutonium is a dense, silvery radioactive metal best known as the explosive core of nuclear weapons and a fuel for nuclear reactors. It's almost entirely synthetic, made in nuclear reactors from uranium, and it has quietly powered some of humanity's most distant spacecraft for decades.
- Group · Period
- — · 7
- At room temp
- solid
- Melts at
- 913 K
- Density
- 19.84 g/cm³
- Discovered
- 1940
Key facts about plutonium
Quick answers, built from the sourced data in the property tables.
- What is the electron configuration of plutonium?
- The electron configuration of plutonium is [Rn] 7s² 5f⁶. Written out in full, that is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 7s² 5f⁶.
- What is the density of plutonium?
- The density of plutonium is 19.84 g/cm³.
- What are the melting and boiling points of plutonium?
- Plutonium melts at 913 K (639.85 °C, 1183.73 °F) and boils at 3501 K (3227.85 °C, 5842.13 °F).
- What is the longest-lived isotope of plutonium?
- Plutonium has no stable isotopes. Its longest-lived known isotope is Pu-244, with a half-life of 8.13 × 10⁷ years.
Uses
Plutonium-239 is the fissile isotope behind both nuclear weapons and mixed-oxide reactor fuel, capable of sustaining the chain reaction that either powers a reactor or releases enormous energy in an instant. A very different isotope, plutonium-238, doesn’t sustain chain reactions well but steadily gives off heat as it decays, which makes it valuable as a compact, long-lasting power source. Radioisotope thermoelectric generators built around plutonium-238 have powered spacecraft including the Voyager probes, the Cassini mission to Saturn, and the Curiosity and Perseverance rovers on Mars, in environments too far from the Sun for solar panels to work well.
History
Plutonium was first produced in late 1940 and early 1941 by Glenn Seaborg, Edwin McMillan, Joseph Kennedy, and Arthur Wahl at Berkeley, who bombarded uranium with deuterons to create it. Its potential as a weapons material was recognized almost immediately, and the discovery was kept classified throughout World War II as the element became central to the Manhattan Project. Plutonium produced in dedicated reactors went on to fuel the Trinity test and the bomb dropped on Nagasaki, and the element’s existence wasn’t made public until after the war ended.
Fun facts
- A plutonium-239 core was used in the Trinity test, the first ever detonation of a nuclear weapon, and in the bomb dropped on Nagasaki in 1945.
- Plutonium-238 has powered NASA's Voyager probes for over 45 years, and both spacecraft are still transmitting data from interstellar space.
- Its discovery in 1941 was kept secret for years because of its wartime significance, not announced publicly until after World War II ended.
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Frequently asked questions
What's the difference between plutonium-238 and plutonium-239?
They're used for almost opposite purposes. Plutonium-239 is fissile and splits readily in a chain reaction, making it the isotope used in nuclear weapons and reactor fuel. Plutonium-238 isn't good at sustaining a chain reaction, but it gives off steady heat as it decays, which is what makes it useful for powering spacecraft.
Does plutonium occur naturally?
Only in extraordinarily tiny traces, formed when uranium ores absorb stray neutrons. For all practical purposes, essentially every gram of plutonium in existence was made deliberately in a nuclear reactor.
Why is it named plutonium?
It continues the naming pattern set by uranium and neptunium, which were named after Uranus and Neptune. Plutonium was named after Pluto, which — like the element — was, at the time, considered the last of its kind.
Compounds
2 notable compounds containing Pu
- PuO2oxide
Plutonium dioxide
A dense, stable ceramic solid with a fluorite structure, the most common and chemically robust form in which plutonium is stored and handled. It resists further oxidation and dissolves only slowly in most acids.
Used for: Fuel component in mixed-oxide (MOX) reactor fuel and radioisotope power sources
- PuF6halide
Plutonium hexafluoride
A volatile, brown-red solid that, like uranium hexafluoride, sublimes readily into a reactive gas. It is markedly less stable than UF₆, and decomposes back to the tetrafluoride under only mild heating.
Isotopes
20 known isotopes
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| Isotope | Natural abundance | Half-life | Decay mode | Mass excess | Binding energy / nucleon | Decay width | Spin/parity | Magnetic moment | Quadrupole moment |
|---|---|---|---|---|---|---|---|---|---|
| Pu-239 | — | 24110 Y | Alpha decay (100%), Spontaneous fission (3.1e-10%) | 48,588.22 keV | 7,560.32 keV | 6.00 × 10-28 eV | 1/2+ | 0.202 μN | -2.319 b |
| Pu-242 | — | 3.73E+5 Y | Alpha decay (100%), Spontaneous fission (0.000553%) | 54,716.88 keV | 7,541.33 keV | 3.88 × 10-29 eV | 0+ | — | — |
| Pu-244 | — | 8.13E+7 Y | Alpha decay (99.877%), Spontaneous fission (0.123%) | 59,806.02 keV | 7,524.82 keV | 1.78 × 10-31 eV | 0+ | — | — |
| Pu-228 | — | 1.1 s | Alpha decay (100%) | 36,107.81 keV | 7,590.4 keV | 4.15 × 10-16 eV | 0+ | — | — |
| Pu-229 | — | 90 s | Alpha decay (100%) | 37,394.92 keV | 7,586.88 keV | 5.07 × 10-18 eV | (3/2+) | — | — |
| Pu-230 | — | 102 s | Alpha decay (100%) | 36,932.17 keV | 7,591 keV | 4.47 × 10-18 eV | — | — | — |
| Pu-231 | — | 8.6 m | Electron capture / beta-plus decay (90%), Alpha decay (10%) | 38,308.58 keV | 7,587.12 keV | 8.84 × 10-19 eV | (3/2+) | — | — |
| Pu-232 | — | 33.8 m | Electron capture (90%), Alpha decay (10%) | 38,360.92 keV | 7,588.98 keV | 2.25 × 10-19 eV | 0+ | — | — |
| Pu-233 | — | 20.9 m | Electron capture / beta-plus decay (99.88%), Alpha decay (0.12%) | 40,051.84 keV | 7,583.8 keV | 3.64 × 10-19 eV | — | — | — |
| Pu-234 | — | 8.8 h | Electron capture (94%), Alpha decay (6%) | 40,349.99 keV | 7,584.61 keV | 1.44 × 10-20 eV | 0+ | — | — |
| Pu-235 | — | 25.3 m | Electron capture / beta-plus decay (99.9972%), Alpha decay (0.0028%) | 42,182.35 keV | 7,578.88 keV | 3.01 × 10-19 eV | (5/2+) | — | — |
| Pu-236 | — | 2.858 Y | Alpha decay (100%), Spontaneous fission (1.9e-7%) | 42,901.51 keV | 7,577.92 keV | 5.06 × 10-24 eV | 0+ | — | — |
| Pu-237 | — | 45.64 d | Electron capture (99.9958%), Alpha decay (0.0042%) | 45,091.66 keV | 7,570.76 keV | 1.16 × 10-22 eV | 7/2- | -0.68 μN | — |
| Pu-238 | — | 87.7 Y | Alpha decay (100%), Spontaneous fission (1.9e-7%) | 46,163.15 keV | 7,568.36 keV | 1.65 × 10-25 eV | 0+ | — | — |
| Pu-240 | — | 6561 Y | Alpha decay (100%), Spontaneous fission (0.0000057%), {+34}Si (1.3e-11%) | 50,125.32 keV | 7,556.04 keV | 2.20 × 10-27 eV | 0+ | — | — |
| Pu-241 | — | 14.329 Y | Beta-minus decay (99.998%), Alpha decay (0.00247%), Spontaneous fission (2.4e-14%) | 52,955.12 keV | 7,546.44 keV | 1.01 × 10-24 eV | 5/2+ | -0.678 μN | 6 b |
| Pu-243 | — | 4.956 h | Beta-minus decay (100%) | 57,754.56 keV | 7,531.01 keV | 2.56 × 10-20 eV | 7/2+ | — | — |
| Pu-245 | — | 10.5 h | Beta-minus decay (100%) | 63,178.17 keV | 7,513.28 keV | 1.21 × 10-20 eV | (9/2-) | — | — |
| Pu-246 | — | 10.84 d | Beta-minus decay (100%) | 65,394.77 keV | 7,506.54 keV | 4.87 × 10-22 eV | 0+ | — | — |
| Pu-247 | — | 2.27 d | Beta-minus decay (100%) | 69,210 keV | 7,493 keV | 2.33 × 10-21 eV | (1/2+) | — | — |
Spin/parity describes the nucleus's intrinsic angular momentum and symmetry. Magnetic moment (in nuclear magnetons, μN) and quadrupole moment (in barns, b) describe the shape of the nucleus's charge distribution — a nonzero quadrupole moment means the nucleus isn't perfectly spherical. These are only measured for a subset of isotopes, mostly stable or long-lived ones, so many rows show "—" rather than a value.