Np=NEPTUNIUM
Neptunium, a radioactive, silver heavy metal, is quite stable for an element with a high and odd atomic number, 237Np has a half-life of 2 million years. On Earth, it naturally occurs in tiny traces in uranium ore, it is found in much bigger amounts as waste in nuclear reactors. It is scarcely used, although it is fissionable. Most of it decays to protactinium.
