The actinide concept in nuclear chemistry was first theorized by Glenn T. Seaborg in 1944, resulting in the correction of Mendeleyev's periodic table of the elements by placing a new actinide series below the lanthanide series. In later theoretical work, Seaborg proposed the transactinide series spanning elements 104-121 and the superactinide series containing elements 122-153. Glenn T. Seaborg Glenn Theodore Seaborg (April 19, 1912 – February 25, 1999) was an American chemist prominent in the discovery and isolation of ten transuranic elements including plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium and seaborgium, which was named in his honor. ... Mendeleyevs portrait by Ilya Repin. ... The periodic table of the chemical elements, also called the Mendeleev periodic table, is a tabular display of the known chemical elements. ... The actinide series encompasses the 14 chemical elements that lie between actinium and nobelium on the periodic table with atomic numbers 89 - 102 inclusive. ... The lanthanide series is the 14 rare earth chemical elements which lie between lanthanum and ytterbium on the periodic table. ... In chemistry, transactinide elements are the chemical elements with atomic numbers greater than 103, the atomic number of lawrencium. ... Superactinides are the undiscovered chemical elements from number 123 (Unbitrium) until 153 (Unpenttrium), at which the 5g and 6f- electron shells are filled up. ...