Definitions for "Neptunium"
A radioactive metallic element of atomic number 93, produced in nuclear reactors from Plutonium or Uranium. Symbol Np; The atomic weight of the most stable isotope is 237.0482.
a radioactive transuranic metallic element; found in trace amounts in uranium ores; a by-product of the production of plutonium
A chemical element with atomic number 93. Neptunium was discovered in 1940 by Philip Hauge Abelson and Edwin McMillan who irradiated sup238/supU with neutrons. It was the first man-made transuranic element. Neptunium was named after the planet Neptune. Symbol: Np.