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How was neptunium first produced and identified in 1940?
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transuranium element
Modern version of the periodic table of the elements (printable).
In 1940, American physicist Edwin Mattison McMillan and chemist Philip Hauge Abelson successfully produced and identified neptunium, the first transuranium element, at the University of California at Berkeley.12
The discovery occurred when the researchers exposed uranium oxide to neutrons generated by a cyclotron. The process involved the following nuclear transformation:12
- The uranium-238 isotope captured a neutron to become uranium-239.1
- Through negative beta-particle decay, a neutron within the uranium-239 nucleus transformed into a proton, emitting a beta particle in the process.1
- This transformation increased the atomic number of the nucleus from 92 to 93, resulting in the creation of neptunium-239.1
This identification marked a significant milestone in nuclear science, as previous attempts by other researchers had mistakenly identified nuclear fission products as new elements. The element was named after the planet Neptune, following the convention established by uranium, which was named after Uranus.123