Which synthetic actinoid element was discovered first?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

A color-coded periodic table of the elements displays each element's symbol and atomic number, with categories such as alkali metals, noble gases, halogens, transition metals, and actinoid elements distinguished by different background colors. — actinoid element Modern version of the periodic table of the elements (printable).

The first synthetic actinoid element to be discovered was neptunium, which has an atomic number of 93.12

It was positively produced and identified in 1940 by American physicists Edwin Mattison McMillan and Philip Hauge Abelson at the University of California at Berkeley. They achieved this by exposing uranium oxide to neutrons from a cyclotron target, a process that resulted in the formation of neptunium through negative beta-particle decay.12