Plutonium

Plutonium, ₉₄Pu
Plutonium
Pronunciation	/pluːˈtoʊniəm/ (ploo-TOH-nee-əm)
Allotropes	see Allotropes of plutonium
Appearance	silvery white, tarnishing to dark gray in air
Mass number	[244]
Plutonium in the periodic table
	neptunium ← plutonium → americium
Atomic number (Z)	94
Group	f-block groups (no number)
Period	period 7
Block	f-block
Electron configuration	[Rn] 5f6 7s2
Electrons per shell	2, 8, 18, 32, 24, 8, 2
Physical properties
Phase at STP	solid
Melting point	912.5 K (639.4 °C, 1182.9 °F)
Boiling point	3505 K (3228 °C, 5842 °F)
Density (near r.t.)	19.85 g/cm3 (239Pu)
when liquid (at m.p.)	16.63 g/cm3
Heat of fusion	2.82 kJ/mol
Heat of vaporization	333.5 kJ/mol
Molar heat capacity	35.5 J/(mol·K)
Atomic properties
Oxidation states	+2, +3, +4, +5, +6, +7, +8 (an amphoteric oxide)
Electronegativity	Pauling scale: 1.28
Ionization energies	1st: 584.7 kJ/mol ; ;
Atomic radius	empirical: 159 pm
Covalent radius	187±1 pm
	Spectral lines of plutonium
Other properties
Natural occurrence	from decay
Crystal structure	monoclinic
Speed of sound	2260 m/s
Thermal expansion	46.7 µm/(m⋅K) (at 25 °C)
Thermal conductivity	6.74 W/(m⋅K)
Electrical resistivity	1.460 µΩ⋅m (at 0 °C)
Magnetic ordering	paramagnetic
Young's modulus	96 GPa
Shear modulus	43 GPa
Poisson ratio	0.21
CAS Number	7440-07-5
History
Naming	after dwarf planet Pluto, itself named after classical god of the underworld Pluto
Discovery	Glenn T. Seaborg, Arthur Wahl, Joseph W. Kennedy, Edwin McMillan (1940–1941)
Isotopes of plutonium v; e;
SF	–
SF	–
SF	–
α	237U
SF	–
SF	–
SF	–
	Category: Plutonium; view; talk; edit; \| references

Plutonium is the chemical element with the atomic number 94 and chemical symbol Pu. It is a highly radioactive metal, and is the metal used in most nuclear weapons. The chemical element plutonium has some different isotopes. The most important isotope of plutonium is ²³⁹Pu (or plutonium-239). It takes 24,110 years for half of a sample of plutonium-239 to decay, which is called its half-life. It can be made from natural uranium. It is fissile and a nuclear fuel.

The isotope that has the longest half-life is ²⁴⁴Pu (or plutonium-244). Plutonium-244 has a half-life of about 80 million years. The half-life of ²⁴⁴Pu is long enough that some of this isotope of plutonium is found in very small amounts in nature. Plutonium-238 is used in Radioisotope Thermoelectric Generators.

Like other transuranium elements, plutonium can react with water, oxygen, carbon, halogens, nitrogen, and silicon. It forms oxides and hydrides in moist air, causing the plutonium sample to expand by up to 70%. Plutonium from the expanding sample can flake off and catch fire at room temperature. Plutonium is also toxic, although it is less toxic than many people think. The reactivity and toxicity of plutonium make it difficult to handle.

It is a solid, at 25 degrees Celsius (77 °F) at standard atmosphere (a pressure). Fresh plutonium has a silvery bright colour but takes on a dull grey, yellow or olive green tarnish when exposed to air.

Plutonium is named after Pluto, a dwarf planet. It is named in the same way as uranium (named after Uranus) and neptunium (named after Neptune).

List of isotopes

²³⁸Pu. The countries that produce the most (as of 2021), are the United States and Russia.
²³⁹Pu
²⁴⁰Pu
²⁴¹Pu
²⁴²Pu
²⁴⁴Pu

Sources

↑ Calculated from the atomic weight and the atomic volume. The unit cell, containing 16 atoms, has a volume of 319.96 cubic Å, according to Siegfried S. Hecker (2000). "Plutonium and its alloys: from atoms to microstructure" (PDF). Los Alamos Science. 26: 331.. This gives a density for ²³⁹Pu of (1.66053906660×10⁻²⁴g/dalton×239.0521634 daltons/atom×16 atoms/unit cell)/(319.96 Å³/unit cell × 10⁻²⁴cc/Å³) or 19.85 g/cc.
↑ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
↑ Magurno & Pearlstein 1981, pp. 835 ff.
↑ https://www.recna.nagasaki-u.ac.jp/recna/en-fmdata/pu_2021. Retrieved 2025-04-26

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[1] Calculated from the atomic weight and the atomic volume. The unit cell, containing 16 atoms, has a volume of 319.96 cubic Å, according to Siegfried S. Hecker (2000). "Plutonium and its alloys: from atoms to microstructure" (PDF). Los Alamos Science. 26: 331.. This gives a density for ²³⁹Pu of (1.66053906660×10⁻²⁴g/dalton×239.0521634 daltons/atom×16 atoms/unit cell)/(319.96 Å³/unit cell × 10⁻²⁴cc/Å³) or 19.85 g/cc.

[NUBASE2020-2] Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.

[FOOTNOTEMagurnoPearlstein1981835_ff-3] Magurno & Pearlstein 1981, pp. 835 ff.

[4] ttps://www.recna.nagasaki-u.ac.jp/recna/en-fmdata/pu_2021. Retrieved 2025-04-26