Edwin McMillan

Edwin McMillan co-discovered neptunium (atomic number 93) in 1940, making it the first synthetic transuranium element ever produced. He also contributed to the discovery of several heavier elements while working at the University of California, Berkeley's Radiation Laboratory.

Neptunium was produced by bombarding uranium with neutrons in a cyclotron at UC Berkeley, generating a beta-decaying product that McMillan and Philip Abelson identified as element 93. The name "neptunium" follows the planetary naming convention established by uranium, named after the planet Uranus.

McMillan shared the 1951 Nobel Prize in Chemistry with Glenn Seaborg for their discoveries in the chemistry of the transuranium elements. Their collaborative work at Berkeley opened the door to the synthesis of an entirely new row of elements on the periodic table.

McMillan independently developed the principle of phase stability, which is fundamental to the operation of synchrotrons and other modern particle accelerators. The concept was also discovered independently by Vladimir Veksler in the Soviet Union, and it enabled accelerators to reach energies far beyond what cyclotrons could achieve.