The radioactive disintegration series is historically known as the Actinium series. Which long-lived — Nuclear Chemistry and Radioactivity Chemistry Question

💡 Solution & Explanation

The Actinium series is the $4n+3$ series. Despite its name (which comes from its first discovered member, Actinium), the actual parent originating nuclide of the entire natural series is the Uranium isotope ${}_{92}^{235}U$.