Neptunium is a synthetic element of the actinides that was produced in 1940 by Edwin McMillan and Philip Abelson. Through bombarding Uranium atoms with neutrons they chemically produced an isotope of Neptunium-239. the element is named after the planet Neptune due to its proximity to uranium which is named after uranus. Much like other actinides it is radioactive and dangerous for handling. It is used to detect neutrons and also in the generation of electricity on spacecrafts. It is a solid metal at room temperature and it has a melting point of 639°c and a boiling point of 4147°c.
E.M. McMillan, P.H. Abelson