Hahn was born in Frankfurt-am-Main, Germany, on March 8, 1879. He studied chemistry at the universities of Munich and Marburg, earning his Ph.D. from Marlburg in 1901. After graduation, he worked successively at the Chemical Institute in Marburg (1902-1903), with William Ramsay at University College, London (1904-1905), and with Rutherford at McGill University in Montreal (1905-1906). In 1906 he joined the Chemical Institute at the University of Berlin. During World War I, he served in the German army.

Hahn's earliest research concerned radioactive elements. He analyzed some of the members of the thorium radioactive family, identifying some of the isotopes that make up that family. In 1918, he discovered the element protactinium with his long-time collaborator, Lise Meitner. Three years later, the two also identified the existence of "nuclear isotopes," atoms that have identical numbers of protons and neutrons in their nuclei, but that decay by different mechanisms.

The achievement for which...