Neptunium

²³⁹Np was discovered by E.M. McMillan and P.H. Abelson in 1940 at Berkeley, California, USA, who bombarded uranium with neutrons produced from a cyclotron. It was the first synthetic transuranium (elements after uranium) element discovered [3].

Named after the planet Neptune, as it is the next planet after Uranus, that gave name to uranium [1]