Neptunium

Neptunium was the first synthetic transuranium element of the actinide series to be discovered. It was first created by Edwin McMillan and Philip H. Abelson in 1940, at the Berkeley Radiation Lab of the University of California. It was created by bombarding isotopes of uranium with other elements. It was named after the planet Neptune, much like uranium was named after Uranus.

Neptunium is a silvery metal, and has to be handled and stored carefully due to it's radioactivity. It has five known oxidation states- and each state produces a different color. Neptunium is often bombarded with neutrons to create plutonium- which is then used in spacecraft generators and terrestrial navigation beacons. Neptunium is also used in neutron detection equipment.