Promethium bond length completes picture of the size of lanthanides’ atoms

Promethium’s coordination structure and bond length with oxygen have been characterised for the first time, filling one of the last gaps in our knowledge of the periodic table.

Promethium, element 61, is part of the lanthanides, which are widely used in modern technology. However, unlike its neighbouring elements, promethium is radioactive, highly unstable and does not exist naturally on Earth. It was only discovered in 1945, when it was created at Oak Ridge National Laboratory, US, by researchers working on the Manhattan Project, which developed the nuclear weapons that ended the second world war. Oak Ridge later played a key role in creating targets for making superheavy elements by nuclear fusion – a role recognised by element 117, tennessine, being named after the lab’s home state.