A former chairman of the U.S. Atomic Energy Commission, Seaborg discovered or co-discovered 9 “transuranium” elements: plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium and nobelium. Later, seaborgium was named in his honor, the first element ever named after a living person. His work earned him a shared Nobel Prize in Chemistry in 1951, and the National Medal of Science in 1991.
His discoveries also led to medical uses of radioactivity, such as the iodine-131 used to treat his mother’s cancer in the 1950s. Seaborg died at home in Lafayette, Calif., on February 26 at age 86, of complications from a stroke.