Neptunium is a chemical element with the symbol Np and atomic number 93. It is a radioactive actinide metal that is primarily produced in nuclear reactors and can also be found in trace amounts in uranium ores. Neptunium is used in research and has potential applications in nuclear science, though it is not commonly found in nature due to its radioactivity and short half-life of its isotopes. Its most stable isotope, neptunium-237, has a half-life of about 2.14 million years.