Answer: Seaborgium

There are quite a few elements on the periodic table named after prominent scientists (some of whom discovered the element in question and some of whom are simply very important contributors to the advancement of human knowledge). Einsteinium, Nobelium, Bohrium, and Copernicium are all named after people such as Albert Einstein, Alfred Nobel, Niels Bohr, and Nicolaus Copernicus.

Among the fifteen elements named after people, however, there is only one element that was named after a person while they were alive to bask in the glow of such an honor: Glenn T. Seaborg for whom the element Seaborgium is named.

You may not have heard of Seaborg or, for that matter, Seaborgium, but he was an accomplished 20th century chemist who was involved in the discovery of ten transuranium elements (including plutonium, americium, curium, and others) and influential in discoveries that led to the current arrangement of the periodic table. He also won the Nobel Prize in Chemistry in 1951, helped with the Manhattan Project, and served as the Chairman of the Atomic Energy Commission.