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
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Sm ↑ Pu ↓ — 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 (at 20° C)	19.85 g/cm3 (239Pu)[1]
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)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 1756 1953 2198 2511 2926 3499
Atomic properties
Oxidation states	common: +4 +2,? +3,[2], +5,[2] +6,[2] +7,[2] +8
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 (mP16)
Lattice constants	a = 0.6183 nm b = 0.4822 nm c = 1.0964 nm β = 101.79° (at 20 °C)[1]
Thermal expansion	49.6×10−6/K (at 20 °C)[1]
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
Speed of sound	2260 m/s
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
Main isotopes[3] Decay abun­dance half-life (t1/2) mode pro­duct 238Pu trace 87.7 y[4] α 234U SF – 239Pu trace 2.411×104 y α 235U SF – 240Pu trace 6.561×103 y α 236U SF – 241Pu synth 14.329 y β− 241Am α 237U SF – 242Pu synth 3.75×105 y α 238U SF – 244Pu trace 8.00×107 y α 240U SF –
Category: Plutonium view talk edit | references

Plutonium is a chemical element; it has symbol Pu and atomic number 94. It is a silvery-gray actinide metal that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states. It reacts with carbon, halogens, nitrogen, silicon, and hydrogen. When exposed to moist air, it forms oxides and hydrides that can expand the sample up to 70% in volume, which in turn flake off as a powder that is pyrophoric. It is radioactive and can accumulate in bones, which makes the handling of plutonium dangerous.

Plutonium was first synthesized and isolated in late 1940 and early 1941, by deuteron bombardment of uranium-238 in the 1.5-metre (60 in) cyclotron at the University of California, Berkeley. First, neptunium-238 (half-life 2.1 days) was synthesized, which then beta-decayed to form the new element with atomic number 94 and atomic weight 238 (half-life 88 years). Since uranium had been named after the planet Uranus and neptunium after the planet Neptune, element 94 was named after Pluto, which at the time was also considered a planet. Wartime secrecy prevented the University of California team from publishing its discovery until 1948.

Plutonium is the element with the highest atomic number known to occur in nature. Trace quantities arise in natural uranium deposits when uranium-238 captures neutrons emitted by decay of other uranium-238 atoms. The heavy isotope plutonium-244 has a half-life long enough that extreme trace quantities should have survived primordially (from the Earth's formation) to the present, but so far experiments have not yet been sensitive enough to detect it.

Both plutonium-239 and plutonium-241 are fissile, meaning they can sustain a nuclear chain reaction, leading to applications in nuclear weapons and nuclear reactors. Plutonium-240 has a high rate of spontaneous fission, raising the neutron flux of any sample containing it. The presence of plutonium-240 limits a plutonium sample's usability for weapons or its quality as reactor fuel, and the percentage of plutonium-240 determines its grade (weapons-grade, fuel-grade, or reactor-grade). Plutonium-238 has a half-life of 87.7 years and emits alpha particles. It is a heat source in radioisotope thermoelectric generators, which are used to power some spacecraft. Plutonium isotopes are expensive and inconvenient to separate, so particular isotopes are usually manufactured in specialized reactors.

Producing plutonium in useful quantities for the first time was a major part of the Manhattan Project during World War II that developed the first atomic bombs. The Fat Man bombs used in the Trinity nuclear test in July 1945, and in the bombing of Nagasaki in August 1945, had plutonium cores. Human radiation experiments studying plutonium were conducted without informed consent, and several criticality accidents, some lethal, occurred after the war. Disposal of plutonium waste from nuclear power plants and dismantled nuclear weapons built during the Cold War is a nuclear-proliferation and environmental concern. Other sources of plutonium in the environment are fallout from many above-ground nuclear tests, which are now banned.