Name Neptunium
Symbol Np
Atomic Number 93
Atomic Mass 237.0 atomic mass units
Number of Protons 93
Number of Neutrons 144
Number of Electrons 93
Melting Point 640.0 C
Boiling Point 3902.0 C
Density 20.45 grams per cubic centimeter
Normal Phase Synthetic
Family Rare Earth Metals
Period 7
Cost Unavailable



Origin of Name After the planet, Neptune
Date and Place of Discovery In 1940 at the Lawrence Berkeley National Laboratory on the University of California campus in Berkeley
Discovered by E. M. McMillan and Philip H. Abelson
Common Compounds
Interesting facts
  • It is found in trace uranium ores.
  • It is fairly reactive chemically.
  • It is the first transuranic element (given a number higher than 92).
Common Uses There are no known uses at this time. However, it is expected to be used in military weaponry.


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