protactinium-231

The long-lived isotope protactinium-231 (originally called protoactinium for “before actinium” and later shortened to protactinium) was discovered (1917) independently by German chemist Otto Hahn and Austrian physicist Lise Meitner in pitchblende, by Fajans, and by British chemists Frederick Soddy, John Cranston, and Sir Alexander Fleck. This isotope

…among the first to isolate protactinium-231, an isotope of the recently discovered radioactive element protactinium. Because nearly all the natural radioactive elements had then been discovered, he devoted the next 12 years to studies on the application of radioactive methods to chemical problems.

…to isolate the isotope protactinium-231 (which they named), studied nuclear isomerism and beta decay, and in the 1930s (along with Strassmann) investigated the products of neutron bombardment of uranium. Because she was Jewish, she left Nazi Germany in the summer of 1938 to settle in Sweden.