Glenn Seaborg was a nuclear chemist who discovered elements 94-102 and 106, which included elements such as plutonium. He also co-discovered neptunium, einsteinium and three other elements. The discovery and co-discoveries of these elements all happened between 1940 and 1955. In 1944 Seaborg suggested a new row to be added to the periodic table called actinides, placed below the lanthanides. This is now the last row on the periodic table containing elements actinium (89) to lawrencium (103).