PLUTONIUM

Introduction

Atomic Number: 94
Group: None
Atomic Weight: 239
Period: 7
CAS Number: 7440-07-5

Classification

Chalcogen
Halogen
Noble Gas
Lanthanoid
Actinoid
Rare Earth Element
Platinum Group Metal
Transuranium
No Stable Isotopes
Solid
Liquid
Gas
Solid (Predicted)

Description • Uses/Function

Plutonium was the second transuranium element of the actinide series to be discovered. The isotope plutonium-238 was produced in 1940 by Seaborg, McMillan, Kennedy, and Wahl by deuteron bombardment of uranium in the 60-inch cyclotron at Berkeley, California. Plutonium also exists in trace quantities in naturally occurring uranium ores. It is formed in much the same manner as neptunium, by irradiation of natural uranium with the neutrons which are present. By far of greatest importance is the isotope plutonium-239, with a half-life of 24,100 years, produced in extensive quantities in nuclear reactors from natural uranium. First, uranium-238 picks up a neutron to give uranium-239, which then undergoes two successive beta decays, to produce neptunium-239 and finally plutonium-239.. Eighteen isotopes of plutonium are now known. Plutonium has assumed the position of dominant importance among the transuranium elements because of its successful use as an explosive ingredient in nuclear weapons and the place which it holds as a key material in the development of industrial use of nuclear power. One kilogram is equivalent to about 22 million kilowatt hours of heat energy. The complete detonation of a kilogram of plutonium produces an explosion equal to about 20,000 tons of chemical explosive. Its importance depends on the nuclear property of being readily fissionable with neutrons and its availability in quantity. The world’s nuclear-power reactors are now producing about 20,000 kg of plutonium/yr. By 1982 it was estimated that about 300,000 kg had accumulated. The various nuclear applications of plutonium are well known. Plutonium-238 has been used in the Apollo lunar missions to power seismic and other equipment on the lunar surface. As with neptunium and uranium, plutonium metal can be prepared by reduction of the trifluoride with alkaline-earth metals. The metal has a silvery appearance and takes on a yellow tarnish when slightly oxidized. It is chemically reactive. A relatively large piece of plutonium is warm to the touch because of the energy given off in alpha decay. Larger pieces will produce enough heat to boil water. The metal readily dissolves in concentrated hydrochloric acid, hydroiodic acid, or perchloric acid with formation of the Pu+3 ion. The metal exhibits six allotropic modifications having various crystalline structures. The densities of these vary from 16.00 to 19.86 g/cm3. Plutonium also exhibits four ionic valence states in aqueous solutions: Pu+3(blue lavender), Pu+4 (yellow brown), PuO+ (pink?), and PuO+2 (pink orange). The ion PuO+ is unstable in aqueous solutions, disproportionating into Pu+4 and PuO+2. The Pu+4 thus formed, however, oxidizes the PuO+ into PuO+2, itself being reduced to Pu+3, giving finally Pu+3 and PuO+2. Plutonium forms binary compounds with oxygen: PuO, PuO2, and intermediate oxides of variable composition; with the halides: Puf3, Puf4, PuCl3, PuBr3, PuI3; with carbon, nitrogen, and silicon: PuC, PuN, PuSi2. Oxyhalides are also well known: PuOCl, PuOBr, PuOI. Because of the high rate of emission of alpha particles and the element being specifically absorbed by bone marrow, plutonium, as well as all of the other transuranium elements except neptunium, are radiological poisons and must be handled with very special equipment and precautions. Plutonium is a very dangerous radiological hazard. Precautions must also be taken to prevent the unintentional formation of a critical mass. Plutonium in liquid solution is more likely to become critical than solid plutonium. The shape of the mass must also be considered where criticality is concerned. Plutonium-238 is available to authorized users from the O.R.N.L. at a cost of about $7.50/mg (97%) plus packing costs of $1250 per package. 1

Physical Properties

Melting Point:2*  640 °C = 913.15 K = 1184 °F
Boiling Point:2* 3228 °C = 3501.15 K = 5842.4 °F
Sublimation Point:2 
Triple Point:2 
Critical Point:2 
Density:3  19.7 g/cm3

* - at 1 atm

Electron Configuration

Electron Configuration:  *[Rn] 7s2 5f6
Block: f
Highest Occupied Energy Level: 7
Valence Electrons: 2

Quantum Numbers:

n = 5
ℓ = 3
m = 2
ms = +½

Bonding

Electronegativity (Pauling scale):4 1.3
Electropositivity (Pauling scale): 2.7

Ionization Potential   eV 5  kJ/mol  
Ionization Potential   eV 5  kJ/mol  
Ionization Potential   eV 5  kJ/mol  
1 6.0262    581.4

Thermochemistry

Specific Heat: 
Thermal Conductivity: 6.74 (W/m)/K, 27°C 6
Heat of Fusion: 2.84 kJ/mol 7 = 11.9 J/g
Heat of Vaporization: 344 kJ/mol 8 = 1439.3 J/g
State of Matter Enthalpy of Formation (ΔHf°)9 Entropy (S°)9 Gibbs Free Energy (ΔGf°)9
(kcal/mol) (kJ/mol) (cal/K) (J/K) (kcal/mol) (kJ/mol)
(s) 0 0 12.3 51.4632 0 0

Isotopes

Nuclide Mass 10 Half-Life 10 Nuclear Spin 10 Binding Energy
228Pu 228.03874(3) 1.1(+20-5) s 0+ 1,738.77 MeV
229Pu 229.04015(6) 120(50) s 3/2+# 1,737.53 MeV
230Pu 230.039650(16) 1.70(17) min 0+ 1,754.91 MeV
231Pu 231.041101(28) 8.6(5) min 3/2+# 1,753.67 MeV
232Pu 232.041187(19) 33.7(5) min 0+ 1,761.74 MeV
233Pu 233.04300(5) 20.9(4) min 5/2+# 1,769.81 MeV
234Pu 234.043317(7) 8.8(1) h 0+ 1,777.89 MeV
235Pu 235.045286(22) 25.3(5) min (5/2+) 1,785.96 MeV
236Pu 236.0460580(24) 2.858(8) a 0+ 1,794.03 MeV
237Pu 237.0484097(24) 45.2(1) d 7/2- 1,802.10 MeV
238Pu 238.0495599(20) 87.7(1) a 0+ 1,810.17 MeV
239Pu 239.0521634(20) 24.11(3)E+3 a 1/2+ 1,808.93 MeV
240Pu 240.0538135(20) 6561(7) a 0+ 1,817.00 MeV
241Pu 241.0568515(20) 14.290(6) a 5/2+ 1,825.07 MeV
242Pu 242.0587426(20) 3.75(2)E+5 a 0+ 1,833.14 MeV
243Pu 243.062003(3) 4.956(3) h 7/2+ 1,831.90 MeV
244Pu 244.064204(5) 8.00(9)E+7 a 0+ 1,839.97 MeV
245Pu 245.067747(15) 10.5(1) h (9/2-) 1,848.04 MeV
246Pu 246.070205(16) 10.84(2) d 0+ 1,846.80 MeV
247Pu 247.07407(32)# 2.27(23) d 1/2+# 1,854.87 MeV
Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses. 10

Abundance

Compounds

Safety Information


Material Safety Data Sheet - ACI Alloys, Inc.

For More Information

External Links:

Magazines:
(1) Biello, David. Trashing the "Element from Hell". Scientific American, July 2012, pp 19.

Sources

(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:23.
(2) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:132.
(3) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 4:39-4:96.
(4) - Dean, John A. Lange's Handbook of Chemistry, 11th ed.; McGraw-Hill Book Company: New York, NY, 1973; p 4:8-4:149.
(5) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 10:178 - 10:180.
(6) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:193, 12:219-220.
(7) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:123-6:137.
(8) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:107-6:122.
(9) - Dean, John A. Lange's Handbook of Chemistry, 12th ed.; McGraw-Hill Book Company: New York, NY, 1979; p 9:4-9:94.
(10) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009).