Plutonium, element 94, was first produced in 1940 at the University of California, Berkeley by chemist Glenn Seaborg and physicist Edwin McMillan. The element is named for the planet Pluto (now officially defined as a dwarf planet), following the pattern set by uranium and neptunium. The first recorded use of the term is by Seaborg and Arthur Wahl in a 1942 government report:
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Since such formulae are confusing when the symbols “93” and “94” are used, we have decided to use symbols of the conventional chemical type to designate these elements. Following McMillan, who has suggested the name neptunium [...] for element 93, we are using plutonium [...] for element 94. The corresponding chemical symbols would be Np and Pu.1
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