Neptunium is a radioactive element with the symbol Np and atomic number 93. It is part of the actinide series in the periodic table and is primarily produced in nuclear reactors through the irradiation of uranium. Neptunium is not found in significant amounts in nature, but it can be created artificially. This element has several isotopes, with Np-237 being the most stable and having a half-life of about 2.14 million years. Neptunium is used in research and has potential applications in nuclear energy and as a source of plutonium for nuclear weapons.