Plutonium Was Named After a Planet Named After a God of Death

The naming of element 94 followed a distinct astronomical pattern established by its predecessors. Uranium, element 92, had been named in honor of the planet Uranus. When element 93 was synthesized at the University of California, Berkeley, in 1940, it was logically named neptunium after the next planet in the solar system, Neptune. Therefore, when Glenn T. Seaborg's team successfully identified element 94 in early 1941, they continued the sequence, naming it plutonium after Pluto, which had been discovered just a decade prior and was then considered the ninth planet.

This cosmic naming convention, however, carried a dark undertone. The planet Pluto had been named for the Roman god of the underworld, a powerful and feared deity who ruled over the dead. The scientists who chose the name "plutonium" were initially more focused on the planetary logic than the mythological symbolism. One of the co-discoverers, Arthur Wahl, even proposed "ultimium" or "extremium" because they thought it might be the last possible element in the periodic table.

The choice of plutonium would prove to be grimly prophetic. Discovered on the cusp of the United States' entry into World War II, the element's unique properties were quickly recognized by the Manhattan Project. Its ability to sustain a nuclear chain reaction made it a key component for atomic weapons. Within just a few years, plutonium formed the fissile core of "Fat Man," the bomb detonated over Nagasaki in 1945. Thus, an element named for a god of death became inextricably linked to one of humanity's most destructive creations.