Polish-American physical chemist · 1887–1975
Kasimir Fajans
Kasimir Fajans co-discovered protactinium in 1913 and helped work out the rules of radioactive decay.
How Protactinium was found
Working in Karlsruhe with his student Oswald Göhring, Fajans found a short-lived isotope in the decay chain of uranium that filled the empty space between thorium and uranium. Because it lasted only about a minute, they named it brevium.
In 1917–18 Otto Hahn and Lise Meitner found a much longer-lived isotope of the same element and called it protoactinium, “before actinium”. The name was shortened to protactinium in 1949.
Shared the credit
The discovery is credited jointly to these scientists.
Life and career
Born 1887 · Died 1975
Fajans was born in Warsaw and worked with Ernest Rutherford in Manchester. In 1913 he and Frederick Soddy independently formulated the displacement law: alpha decay moves an element two places back in the periodic table, beta decay one place forward.
He became professor in Munich, but left Germany in 1935 and spent the rest of his career at the University of Michigan. Fajans’ rules, which predict whether a chemical bond will be ionic or covalent, are still taught.
Also known for
- The radioactive displacement law
- Fajans’ rules of chemical bonding
Discovered in the same era
Other elements identified within ten years of 1913.