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About Plutonium

Plutonium Bohr

Plutonium, as with other members of the actinide series, is highly radioactive. Plutonium differentiates itself from the rest of the group by being one of only three primary fissile isotopes in use (239Pu) – [the other two include 233U and 235U] – to produce and sustain a nuclear chain reaction when struck by a slow moving neutron. In fact, just one kilogram of 239Pu can produce an explosion equivalent to 21,000 tons of chemical explosives. Its primary applications include weapons and power or fuel generation, and its applicability is determined by the fractional amount of spontaneously fissile 240Pu contained in the system. Weapons-grade plutonium has the smallest amount of 240Pu dilution (<7%), while power-grade plutonium has the largest amount of 240Pu present (>19%). Additionally, other isotopes have been used for very specific applications: 238Pu is used in radioisotope thermoelectric generators on deep-space spacecraft, and 233Pu was used for power systems on lunar equipment set in place during the Apollo program. The choice of which particular plutonium isotope to use is determined by application requirements and half-life characteristics of the isotope.

Plutonium’s most stable isotope (244Pu) has a half-life around 80 million years – long enough for trace amounts (parts-per-trillion) to remain present in the Earth’s crust. Discovery of plutonium in the laboratory was necessitated by the scarce amount of this element available in nature. First falsely discovered by Enrico Fermi in 1934, plutonium was first synthesized by Glenn Seaborg (under Edwin McMillan’s leadership) at Berkeley Radiation Laboratory in 1940 through deuteron bombardment of uranium. The official discovery was predicated upon uranium research that Egon Bretscher and Norman Feather had experimented upon at the Cavendish Laboratory in Cambridge. While the discovery and first synthesization was complete in 1940, the fact of plutonium’s existence was not known publicly until 1946 – after conclusion of the primary motivation for the Manhattan Project. The United States’ very first atomic weapon test (“Trinity”) as well as the second atomic bomb dropped on Japan (“Fat Man” – Nagasaki), used plutonium as its fissile material. The Nuclear Test Ban Treaty was set in place partly due to concerns over worldwide plutonium contamination.

Plutonium is a silvery-gray metal and oxidizes readily when exposed to air. When exposed to moist air, the volume of the plutonium sample can increase 70%, causing powder to flake off and spontaneously ignite. Other atypical observations of plutonium include its increased density when it melts and its resistivity increases when its temperature is lowered – both unusual traits of metals. Plutonium’s complicated phase diagram also makes machining plutonium difficult as its states easily change through several allotropes depending on its environmental conditions. Due to its reactive nature, plutonium combines with many other elements to form compounds and metal alloys, none of which have any applicability outside of fundamental scientific research Plutonium has twenty known isotopes, many with applications described earlier. Over time, plutonium isotopes = 244 typically decays into uranium and neptunium via alpha decay. Isotopes >244 typically decay into americium through beta decay.

Plutonium Properties

Plutonium Bohr ModelPlutonium is a Block F, Group 3, Period 7 element. The number of electrons in each of Plutonium's shells is 2, 8, 18, 32, 24, 8, 2 and its electronic configuration is [Rn] 5f6 7s2. In its elemental form, CAS 7440-07-5, plutonium has a silvery white appearance. The plutonium atom has a radius of and its Van der Waals radius is Plutonium is found in some concentrated ores of uranium. Plutonium was discovered by Glenn T. Seaborg, Edwin M. McMillan, J. W. Kennedy and A. C. Wahl in 1940. The element Plutonium was named after the former planet Pluto.

Plutonium is radioactive and toxic. Plutonium information, including technical data, safety data and its properties, research, applications and other useful facts are discussed below. Scientific facts such as the atomic structure, ionization energy, abundance on Earth, conductivity and thermal properties are included.

Symbol: Pu
Atomic Number: 94
Atomic Weight: 244
Element Category: Actinide
Group, Period, Block: n/a, 7, f
Color: silvery white
Other Names: Plutonio
Melting Point: 640°C, 1184°F, 913.15 K
Boiling Point: 3228°C, 5842.4°F, 3501.15 K
Density: 19814 kg·m3
Liquid Density @ Melting Point: 16.63 g·cm3
Density @ 20°C: 19.8 g/cm3
Density of Solid: 19816 kg·m3
Specific Heat: N/A
Superconductivity Temperature: N/A
Triple Point: N/A
Critical Point: N/A
Heat of Fusion (kJ·mol-1): 2.8
Heat of Vaporization (kJ·mol-1): 343.5
Heat of Atomization (kJ·mol-1): 348
Thermal Conductivity: 6.74 W·m-1·K-1
Thermal Expansion: (25 °C) 46.7 µm·m-1·K-1
Electrical Resistivity: (0 °C) 1.460 nΩ·m
Tensile Strength: N/A
Molar Heat Capacity: 35.5 J·mol-1·K-1
Young's Modulus: 96 GPa
Shear Modulus: 43 GPa
Bulk Modulus: N/A
Poisson Ratio: 0.21
Mohs Hardness: N/A
Vickers Hardness: N/A
Brinell Hardness: N/A
Speed of Sound: 2260 m·s-1
Pauling Electronegativity: 1.28
Sanderson Electronegativity: N/A
Allred Rochow Electronegativity: 1.22
Mulliken-Jaffe Electronegativity: N/A
Allen Electronegativity: N/A
Pauling Electropositivity: 2.72
Reflectivity (%): N/A
Refractive Index: N/A
Electrons: 94
Protons: 94
Neutrons: 150
Electron Configuration: [Rn] 5f6 7s2
Atomic Radius: 159 pm
Atomic Radius,
non-bonded (Å):
Covalent Radius: 187±1 pm
Covalent Radius (Å): 1.8
Van der Waals Radius: 243 pm
Oxidation States: 6, 5, 4, 3
Phase: Solid 
Crystal Structure: monoclinic
Magnetic Ordering: paramagnetic
Electron Affinity (kJ·mol-1) Unknown
1st Ionization Energy: 584.7 kJ·mol-1
2nd Ionization Energy: N/A
3rd Ionization Energy: N/A
CAS Number: 7440-07-5
EC Number: N/A
MDL Number: N/A
Beilstein Number: N/A
SMILES Identifier: [Pu]
InChI Identifier: InChI=1S/Pu
PubChem CID: 23940
ChemSpider ID: 22382
Earth - Total: N/A
Mercury - Total: N/A
Venus - Total: N/A
Earth - Seawater (Oceans), ppb by weight: N/A
Earth - Seawater (Oceans), ppb by atoms: N/A
Earth -  Crust (Crustal Rocks), ppb by weight: N/A
Earth -  Crust (Crustal Rocks), ppb by atoms: N/A
Sun - Total, ppb by weight: N/A
Sun - Total, ppb by atoms: N/A
Stream, ppb by weight: N/A
Stream, ppb by atoms: N/A
Meterorite (Carbonaceous), ppb by weight: N/A
Meterorite (Carbonaceous), ppb by atoms: N/A
Typical Human Body, ppb by weight: N/A
Typical Human Body, ppb by atom: N/A
Universe, ppb by weight: N/A
Universe, ppb by atom: N/A
Discovered By: Glenn T. Seaborg, Arthur Wahl, Joseph W. Kennedy, Edwin McMillan
Discovery Date: 1940
First Isolation: N/A

Plutonium Isotopes

Plutonium is an artificial element. It has no stable isotopes.

Nuclide Isotopic Mass Half-Life Mode of Decay Nuclear Spin Magnetic Moment Binding Energy (MeV) Natural Abundance
(% by atom)
228Pu 228.03874(3) 1.1(+20-5) s a to 224U; ß+ to 228Np 0+ N/A 1708.52 -
229Pu 229.04015(6) 120(50) s a to 225U 3/2+# N/A 1707.28 -
230Pu 230.039650(16) 1.70(17) min a to 226U; ß+ to 230Np 0+ N/A 1724.68 -
231Pu 231.041101(28) 8.6(5) min ß+ to 231Np; a to 227U 3/2+# N/A 1723.44 -
232Pu 232.041187(19) 33.7(5) min EC to 232Np; a to 228U 0+ N/A 1731.52 -
233Pu 233.04300(5) 20.9(4) min ß+ to 233Np; a to 229U 5/2+# N/A 1739.6 -
234Pu 234.043317(7) 8.8(1) h EC to 234Np; a to 230U 0+ N/A 1747.68 -
235Pu 235.045286(22) 25.3(5) min ß+ to 235Np; a to 231U (5/2+) N/A 1755.76 -
236Pu 236.0460580(24) 2.858(8) y a to 232U 0+ N/A 1763.84 -
237Pu 237.0484097(24) 45.2(1) d EC to 237Np; a to 232U 7/2- N/A 1771.91 -
238Pu 238.0495599(20) 87.7(1) y a to 234U; SF 0+ N/A 1779.99 -
239Pu 239.0521634(20) 24.11(3)E+3 y a to 235U; SF 1/2+ 0.203 1778.76 -
240Pu 240.0538135(20) 6561(7) y a to 236U; SF 0+ N/A 1786.83 -
241Pu 241.0568515(20) 14.290(6) y a to 237U; SF ; ß- to 241Am 5/2+ -0.683 1794.91 -
242Pu 242.0587426(20) 3.75(2)E+5 y a to 238U; SF 0+ N/A 1802.99 -
243Pu 243.062003(3) 4.956(3) h ß- to 243Am 7/2+ N/A 1801.75 -
244Pu 244.064204(5) 8.00(9)E+7 y a to 240U; SF 0+ N/A 1809.83 -
245Pu 245.067747(15) 10.5(1) h ß- to 245Am (9/2-) N/A 1817.91 -
246Pu 246.070205(16) 10.84(2) d ß- to 246Am 0+ N/A 1816.67 -
247Pu 247.07407(32)# 2.27(23) d ß- to 247Am 1/2+# N/A 1824.75 -