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Symbol Np
Atomic Number 93
Atomic Mass 237 g.mol -1
Discovered by Edwin McMillan and Philip Abelson in 1940

Chemical Properties of Neptunium

Group Actinides Melting point 644°C, 1191°F, 917 K 
Period 7 Boiling point 3902°C, 7056°F, 4175 K
Block f Density (g cm−3) 20.2 
Atomic number 93 Relative atomic mass [237]    
State at 20°C Solid Key isotopes 237Np
Electron configuration [Rn] 5f46d17s2  CAS number 7439-99-8
ChemSpider ID 22375 ChemSpider is a free chemical structure database

What is Neptunium?

  • Neptunium has an atomic number of 93, present in the actinide series of on the Periodic Table.
  • Neptunium is found between uranium (92), the last of the natural elements, and plutonium (94).
  • Like its two closest neighbours, it belongs to the actinide series, so named because of the chemical affinity with actinium (89).
  • First, of the artificially produced elements, Np starts the series of the 11 transuranic elements, all radioactive, heavy metals.

Physical Properties of Neptunium

  • 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).
  • Neptunium 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, Neptunium 237 also appears in increasing quantity as a product of americium 241.

Applications and Effects of Neptunium

  • With a critical mass of 73 kg, Neptunium is considered usable in nuclear weapons. Although, no country is known to have used it to make a nuclear explosive device.
  • Neptunium with no major commercial uses of Np is needed for research and exploratory work.

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