Discovery of neptunium

Neptunium was discovered in 1940 by the American physicists Edwin McMillan and Philip Abelson at the University of California, Berkeley. They bombarded uranium with neutrons in a cyclotron and found that some of the uranium nuclei captured a neutron and then decayed into a new element with an atomic number of 93. It was the first transuranium element, meaning one heavier than uranium, to be produced and identified. It was named after Neptune, the planet beyond Uranus, just as uranium had been named after Uranus. Neptunium itself decays into plutonium, the next element, which was identified soon afterwards. It is a radioactive, silvery metal, and traces form naturally in uranium ores, while larger amounts are created as a by-product in nuclear reactors.

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