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 was first discovered in 1940 by scientists Edwin McMillan and Philip H. Abelson. Neptunium is primarily produced in nuclear reactors and can be used in various applications, including research and potential use in nuclear batteries. As a metal, neptunium is silvery and can tarnish when exposed to air. It has several isotopes, with Np-237 being the most stable and having a half-life of about 2.14 million years. Neptunium is not found naturally in significant amounts and is typically obtained through the irradiation of uranium.