Darleane Hoffman was a trailblazing nuclear chemist whose work helped to extend the periodic table and deepen our understanding of the heaviest elements. The transuranic elements - those with an atomic number higher than uranium's 92 - are all unstable and radioactive. Her discovery of naturally occurring plutonium-244 overturned the long-held premise that uranium-238 was the heaviest element found in nature. Her research influenced our understanding of nuclear fission, advanced cancer therapies and improved nuclear-waste-management protocols. She has died aged 98.