Actinium’s radius revised to solve cancer therapy mystery

The ionic radius of actinium(III) may be far smaller and closer to the lanthanides than the most recent measurements from the 1950s and 70s suggest, a review by researchers at Lawrence Livermore National Laboratory, US, has found. This could have potential ramifications for cancer therapies.

Actinium was discovered by French chemist André-Louis Debierne in 1899. But it exists in such small quantities naturally – usually from the radioactive decay of heavier elements – that it can’t be extracted and used in experiments. Instead, researchers rely on actinium created in nuclear reactors. Even so, the element is often in short supply, with only microgram quantities available to a handful of teams around the world.