An under-the-wire atomic discovery

A team of research chemists racing against the laws of nature have completed the first study of the element einsteinium in more than 40 years. In a Feb. 3 report published in the journal Nature, scientists associated with the Berkeley Lab, the University of California, Los Alamos National Laboratory, and Georgetown University pinned down at least one crucial chemical property of the metal and illuminated a rarely investigated corner of the periodic table. The discoveries required speed and precision.

Scientists first observed einsteinium in the fallout from the first hydrogen bomb test during Operation Ivy in 1952. The force of the 10.4 megaton blast over Enewetak Atoll in the Marshall Islands smashed new elements and isotopes together, including einsteinium. Eventually scientists for the University of California, Berkeley were able to identify 200 individual atoms of einsteinium found in radioactive debris from the explosion. Since then, scientists have manufactured tiny amounts of the super-heavy element in labs. But they hadn’t studied it since the 1970s.

During the experiments, the team measured the distance between two bonded einsteinium atoms for the first time. An element’s bond distance is a basic piece of information that helps scientists predict how it will react to other elements. The fact that researchers didn’t know einsteinium’s until now highlights how difficult it is to study.

Einsteinium’s 99 protons and electrons place it at the bottom of the periodic table of elements among a group of 15 metals known as actinoids. The series occupies atomic numbers 89 through 103. Like the actinoid uranium, einsteinium is highly radioactive and dangerous to work with. Unlike uranium, researchers haven’t found the silvery-white metal in nature and can only create it by applying significant force.

The researchers turned to the Oak Ridge National Laboratory for help. Scientists at Oak Ridge bombarded curium atoms with sub-atomic particles until they had created 233 nanograms of einsteinium for the research chemists. It’s difficult enough to create the element. But it was only a tiny amount—if researchers duplicated the process 1 billion times, they could make enough einsteinium to fill an 8-ounce glass.

Additionally, the einsteinium-254 isotope has a half-life of just 276 days, meaning that after just over nine months, half of it would decay and turn into an isotope of berkelium that emits dangerous gamma radiation. “It’s decaying consistently, so you lose 7.2 percent of your mass every month when studying it,” study co-author and former Berkeley Lab chemist Korey Carter told LiveScience. “You have to take this into account when you are planning your experiments.”

The outbreak of the coronavirus pandemic just after Oak Ridge turned over the einsteinium sample caused delays significant enough to cancel some of the planned experiments. Racing against their own diminishing stock of the element, scientists were able to take some significant measurements, including the typical bond distance of two einsteinium atoms at 2.38 angstroms—about 2 percent closer than expected.

“Determining the bond distance may not sound interesting, but it’s the first thing you would want to know about how a metal binds to other molecules,” study co-author Rebecca Abergel told Laboratory Equipment. “What kind of chemical interaction is this element going to have with other atoms and molecules?”

At present, einsteinium has no commercial value. But some scientists hope that by refining the methods to create relatively stable isotopes like einsteinium-254, future chemists could use that element as a platform to create other, heavier synthetic elements. Just as researchers used curium to make einsteinium, they hope to one day use einsteinium as a springboard to jump to the long-theorized “island of stability”—a group of yet-to-be created elements that they predict will be more stable than many of the actinoids.