Seaborg's Periodic Table
Into the 1930s the heaviest elements were being put up in the body of the periodic table, and Glenn Seaborg "plucked those out" while working with Fermi in Chicago, naming them the Actinide series, which later permitted proper placement of subsequently 'created' elements - the Transactinides, changing the periodic table yet again. These elements were shown separate from the main body of the table.
In this connection, Seaborg demonstrated that the heavy elements form a "transition" series of actinide elements in a manner analogous to the rare-earth series of lanthanide elements. The concept demonstrated how the heavy elements fit into the Periodic Table and thus demonstrated their relationships to the other elements. In addition to the discovery of transuranium elements, Seaborg and his colleagues are responsible for the identification of more than 100 isotopes of elements throughout the Periodic Table.