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94 Pu (244)

Plutonium

Actinoid
Symbol Pu
Atomic Number 94
Atomic Weight (244)
CAS Registry ID 7440-07-5
Group Name Actinoid
Period Number 7
Block f-block
State at STP Solid

Description

Sample of Plutonium ⌕ Enlarge Image

Plutonium is an actinide that has a silvery white color in its natural solid appearance. This element is known for its unusual chemical characteristics including the fact that it has six allotropes, is sensitive to atmospheric changes, and it become brittle with time due to its characteristic to self-irradiate itself. Plutonium has an atomic weight of 244, a melting point of 1182.9 °F, and a boiling point of 5842 °F. Plutonium is used to power pacemakers, and as a component in nuclear weapons.

Isolation

Plutonium exists naturally in the crust of the Earth and in uranium ores. Most of the plutonium that is used for commercial purposes though is artificially synthesized.

Plutonium ⌕ Enlarge Image

The artificial creation of plutonium takes place using uranium. The first creation of plutonium was carried out by using the deuteron bombardment of uranium. Plutonium that was subsequently produced for use in the first atomic bomb was produced in a graphite reactor. Today, plutonium is created by bombarding uranium-233 with neutrons. This bombardment takes place in a nuclear reactor. As uranium is used to fuel the reactor, plutonium is continually produced from the nuclear reactors. Another process that can be used to create a different isotope of plutonium uses neptunium; once neptunium is produced from the decay of uranium-237, it can be chemically separated and irradiated by reactor neutrons to form another isotope, neptunium 238. This isotope then decays to form the isotope of plutonium Pu-238. Plutonium is extremely toxic and dangerous; disposal problems of excess plutonium have been causing environmental concerns.

General

NamePlutonium
SymbolPu
Number94
Chemical seriesActinoid
Groupn/a
Period7
Blockf
Appearancesilvery white
Standard atomic weight(244) g·mol⁻¹
Electron configuration[Rn] 5f6 7s2
Electrons per shell2, 8, 18, 32, 24, 8, 2

Atomic Properties

Crystal structuremonoclinic
Oxidation states6, 5, 4, 3 (amphoteric oxide)
Electronegativity1.28 (scale Pauling)
Ionization energies1st: 584.7 kJ/mol
Atomic radius175 pm
Atomic radius (calc.)
Covalent radius
Van der Waals radius

Physical Properties

Phasesolid
Density (near r.t.)19.816  g·cm−3
Liquid density at m.p.16.63  g·cm−3
Melting point912.5 K (639.4 °C, 1182.9 °F)
Boiling point3505 K (3228 °C, 5842 °F)
Critical point
Heat of fusion2.82  kJ·mol−1
Heat of vaporization333.5  kJ·mol−1
Heat capacity(25 °C) 35.5  J·mol−1·K−1

Miscellaneous

Magnetic ordering
Electrical resistivity(0 °C) 1.460 µΩ·m
Thermal conductivity(300 K) 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 modulus96 GPa
Shear modulus43 GPa
Bulk modulus
Poisson ratio0.21
Mohs hardness
Vickers hardness
Brinell hardness