Neptunium is a chemical element with the symbol Np and atomic number 93. A radioactive metal, neptunium is the first transuranic element, and belongs to the actinide series. Its most stable isotope, 237Np, is a by-product of nuclear reactors and plutonium production, and it can be used as a component in neutron detection equipment. Neptunium is also found in trace amounts in uranium ores due to transmutation reactions.Symbol: Np
Electron configuration: Rn 5f4 6d1 7s2
Discovered: 1940
Melting point: 638.8 °C
Atomic number: 93
Atomic mass: 237 u