Neptunium Chemical Element Properties

Neptunium is a chemical element with the symbol Np and atomic number 93. It is a radioactive actinide metal, neptunium is the first transuranic element. Its position in the periodic table just after uranium, named after the planet Uranus, led to it being named after Neptune, the next planet beyond Uranus. A neptunium atom has 93 protons and 93 electrons, of which seven are valence electrons. Neptunium metal is silvery and tarnishes when exposed to air. The element occurs in three allotropic forms and it normally exhibits five oxidation states, ranging from +3 to +7. It is radioactive, poisonous, pyrophoric, and capable of accumulating in bones, which makes the handling of neptunium dangerous.

Neptunium Properties
Symbol Np
Atomic Number 93
Atomic Mass 237 g.mol -1
Discovered by Edwin McMillan and Philip Abelson in 1940
electron configuration [Rn]5f 46d17s2

Chemical Properties of Neptunium

  • It is a hard, silvery, ductile, radioactive actinide metal. In the periodic table, it is located to the right of the actinide uranium, to the left of the actinide plutonium, and below the lanthanide promethium.
  • Neptunium metal is similar to uranium in terms of physical workability. When exposed to air at normal temperatures, it forms a thin oxide layer.
  • It found in at least three allotropes. Some claims of a fourth allotrope have been made, but they are so far not proven.
  • The crystal structures of neptunium, protactinium, uranium, and plutonium do not have clear analogs among the lanthanides and are more similar to those of the 3d transition metals.


Physical Properties of Np

  • Like plutonium and uranium, neptunium (237) is an alpha emitter, which means that as it disintegrates, it emits a particle formed of two protons and two neutrons (similar to a helium nucleus). It then transmutes into protactinium 233 (element 91).
  • It is produced through neutron bombardment of a uranium nucleus.
  • Plutonium 238 is obtained as a result of using Np 237 as a target in research reactors, which constitutes a significant source of energy for space missions.
  • Found in nuclear waste as a mixture with other fission products, Np 237 also appears in increasing quantity as a product of americium 241.

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