Plutonium

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Plutonium is a rare radioactive, metallic and toxic chemical element. It has the symbol Pu and the atomic number 94. It is a fissile element used in most modern nuclear weapons. The most significant isotope of plutonium is 239Pu, with a half-life of 24,100 years. It can be made from natural uranium. The most stable isotope is 244Pu, with a half-life of about 80 million years, long enough to be found in extremely small quantities in nature, making 244Pu the nucleon-richest atom that naturally occurs in the Earth's crust, albeit in small traces.

 

General
Name, Symbol, Number plutonium, Pu, 94
Chemical series actinides
Group, Period, Block n/a, 7, f
Appearance silvery white
Standard atomic weight (244) g·mol-1
Electrons per shell 2, 8, 18, 32, 24, 8, 2
Physical properties
Phase solid
Density (near r.t.) 19.816 g·cm−3
Liquid density at m.p. 16.63 g·cm−3
Melting point 912.5K
(639.4°C, 1182.9°F)
Boiling point 3505K
(3228°C, 5842°F)
Heat of fusion 2.82 kJ·mol-1
Heat of vaporization 333.5 kJ·mol-1
Heat capacity (25°C) 35.5 J·mol-1·K-1
Vapor pressure
P(Pa) 1 10 100 1 k 10 k 100 k
at T(K) 1756 1953 2198 2511 2926 3499
Atomic properties
Crystal structure monoclinic
Oxidation states 6, 5, 4, 3
(amphoteric oxide)
Electronegativity 1.28 (Pauling scale)
Ionization energies 1st: 584.7 kJ/mol
Atomic radius 175 pm
Miscellaneous
Magnetic ordering no data
Electrical resistivity (0 °C) 1.460 µΩ·m
Thermal conductivity (300K) 6.74 W·m-1·K-1
Thermal expansion (25°C) 46.7 µm·m-1·K-1
Speed of sound (thin rod) (20 °C) 2260 m/s
Young's modulus 96 GPa
Shear modulus 43 GPa
Poisson ratio 0.21
CAS registry number 7440-07-5

 

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