Look up every key property of Plutonium (Pu, Z=94) — from atomic mass and electron configuration to melting point, oxidation states, and nuclear applications.
Pu94
Plutonium (Plutonium)
Atomic number 94 · f-block · Period 7 · Actinide
A radioactive transuranic metal with six allotropic phases — the primary fissile material in nuclear weapons and a heat source for deep-space RTGs.
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Identity & Classification
Atomic Structure
Physical Properties
Thermodynamic Properties
Chemical Properties
Notable Isotopes
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Summary
Look up every key property of Plutonium (Pu, Z=94) — from atomic mass and electron configuration to melting point, oxidation states, and nuclear applications.
How it works
The page loads a curated dataset of Plutonium properties organized by category.
Properties are grouped into thematic sections: identity, atomic structure, physical, thermodynamic, chemical, and isotopes.
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Isotope data covers naturally occurring trace isotopes and key artificial isotopes with half-lives.
Use cases
Quick reference during nuclear chemistry or physics coursework.
Verify data for lab reports and research papers on actinides.
Study periodic trends at the heavy end of the actinide series.
Engineering calculations for plutonium fuel elements and reactor design.
Compare plutonium isotopes for nuclear fuel cycle and waste management analysis.
Teaching radioactive decay, fission, and transuranic element properties.
Research on plutonium metallurgy and its unusual allotropic behavior.
Environmental and radiological safety assessments involving plutonium.
Frequently Asked Questions
When Glenn Seaborg and his team discovered element 94 in 1940, they named it plutonium after the dwarf planet Pluto, continuing the pattern established by uranium (Uranus) and neptunium (Neptune). The symbol Pu was chosen using the first and third letters of the name — reportedly also because "Pp" sounded unappealing. Seaborg later said the unusual abbreviation was partly a deliberate inside joke among the discovery team.
Plutonium exists in nature only in vanishingly small trace amounts. Pu-239 is produced when U-238 in uranium ore captures a neutron from spontaneous fission or cosmic-ray interactions. The total amount of naturally occurring plutonium on Earth is estimated at less than a gram, distributed across large uranium ore deposits. All significant quantities of plutonium are synthetic, produced in nuclear reactors by neutron bombardment of U-238.
Plutonium has six allotropic phases (alpha through epsilon) at ambient pressure and a seventh (zeta) at high pressure. This unusual behavior arises from competing interactions between its 5f electrons and the conduction band electrons. Small changes in temperature cause dramatic rearrangements of the crystal structure, resulting in density changes of up to 25% between phases. The delta phase, which is face-centered cubic and less dense than the alpha phase, is particularly intriguing and is stabilized at room temperature by adding small amounts of gallium or aluminum.
The primary use of Pu-239 is as a fissile material in nuclear weapons and as fuel in mixed-oxide (MOX) reactor fuel. Pu-238, which produces significant heat through radioactive decay (~0.55 W/g), is used as a heat source in radioisotope thermoelectric generators (RTGs) that power deep-space spacecraft such as Voyager, Cassini, and the Mars Curiosity and Perseverance rovers. Pu-241 is a precursor to Am-241, which is used in smoke detectors.
Plutonium poses a significant radiological hazard primarily if inhaled as fine particles, because alpha-emitting particles become lodged in lung tissue. External exposure is less concerning since alpha radiation cannot penetrate skin. However, plutonium is also chemically toxic, behaving similarly to calcium in the body and accumulating in bone. The critical mass for a bare sphere of Pu-239 is about 10 kg (compared to ~52 kg for U-235), making it a material of extreme security concern.
Pu-244 has the longest half-life of any plutonium isotope at about 80.8 million years, long enough that trace amounts survive in nature. However, the most important isotopes are Pu-239 (half-life 24,110 years, fissile, primary weapons/reactor material) and Pu-238 (half-life 87.7 years, primary RTG heat source). Pu-240 is an unavoidable contaminant in reactor-grade plutonium and complicates weapon design due to its high spontaneous fission rate.