Neptunium

93

Np

(237)
  • Name: Neptunium
  • Symbol: Np
  • Atomic number: 93
  • Atomic weight: (237)
  • CAS Registry ID: 7439-99-8
  • Group name: Actinoid
  • Period number: 7
  • Block: f-block
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Description

Neptunium is an actinide that is a silver metallic color in its natural solid state. It has radioactive properties, is chemically reactive, and it is a transuranic element. Neptunium has an atomic number of 237, a melting point of 1179 °F, and a boiling point of 7232 °F. Neptunium is not used commercial as it is rare, radioactive, and toxic. The main use for neptunium today is as a basis to create the isotope, number 238, of plutonium which is used for military and spacecraft purposes.

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Isolation

While neptunium has no commercial value, it is still extracted and isolated from sources. It can also be collected as a by-product from certain processes.

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Minute amounts of neptunium can be found in uranium containing ores. A transmutation of uranium in the ore decays the uranium and slowly produces the tiny amounts of neptunium over time. However, these sources are not usually used for extracted purposes. When it is isolated, neptunium is reduced to its isotopic fluoride form, number 237, and undergoes a reduction reaction with barium or lithium vapors. The reaction takes place under heated conditions of around 2192 °F. More often, neptunium is collected as a by product produced in nuclear fuel rods that are used in plutonium production. Neptunium has a very short half life, and so isolated extracts of this element must be used quickly for their purposes before they decay. The most stable isotope of neptunium, number 236, only has a half life of 22.5 hours. Neptunium will decay to form bismuth over time. Nuclear synthesis procedures are also used to produce neptunium.
General
Name Neptunium
Symbol Np
Number 93
Chemical series actinides
Group n/a
Period 7
Block f
Appearance silvery metallic
Standard atomic weight (237)  g·mol−1
Electron configuration [Rn] 5f4 6d1 7s2
Electrons per shell 2, 8, 18, 32, 22, 9, 2
Atomic properties
Crystal structure orthorhombic, tetragonal, cubic
Oxidation states 6, 5, 4, 3 (amphoteric oxide)
Electronegativity 1.36 (scale Pauling)
Ionization energies 1st: 604.5 kJ/mol
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Atomic radius 175  pm
Atomic radius (calc.)
Covalent radius
Van der Waals radius
Physical properties
Phase solid
Density (near r.t.) 20.2  g·cm−3
Liquid density at m.p.
Melting point 910 K (637 °C, 1179 °F)
Boiling point 4273 K (4000 °C, 7232 °F)
Critical point
Heat of fusion 3.20  kJ·mol−1
Heat of vaporization 336  kJ·mol−1
Heat capacity (25 °C) 29.46  J·mol−1·K−1
Miscellaneous
Magnetic ordering
Electrical resistivity (22 °C) 1.220 µΩ·m
Thermal conductivity (300 K) 6.3  W·m−1·K−1
Thermal expansion
Speed of sound (thin rod)
Young's modulus
Shear modulus
Bulk modulus
Poisson ratio
Mohs hardness
Vickers hardness
Brinell hardness
CAS registry number 7439-99-8

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