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Scientists measure bond distance in rare, radioactive element einsteinium

Because einsteinium has such a short half-life, researchers at the University of California, Berkeley had to work fast when conducting experiments with element 99. Photo by Marilyn Sargent/Berkeley Lab
Because einsteinium has such a short half-life, researchers at the University of California, Berkeley had to work fast when conducting experiments with element 99. Photo by Marilyn Sargent/Berkeley Lab

Feb. 3 (UPI) -- Scientists have, for the first time, measured the bond distance of einsteinium, one of the most radioactive and difficult to make elements on the periodic table.

Researchers detailed rare experiments on the element, which carries the atomic number 99, in a paper published Wednesday in the journal Nature.

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With little known about the chemical properties of einsteinium, bond distance -- the average distance between the nuclei of two bonded atoms in a molecule -- is key to understanding how an element will interact with other atoms and molecules.

"[The finding] is significant because the more we understand about its chemical behavior, the more we can apply this understanding for the development of new materials or new technologies," study author Rebecca Abergel said in a press release.

"Not necessarily just with einsteinium, but with the rest of the actinides" elements -- the 15 radioactive, heavier, unstable elements between atomic numbers 89 and 103 -- said Abergel, an assistant professor of nuclear engineering at the University of California, Berkeley.

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Chemical engineers at at the Department of Energy's Lawrence Berkeley National Laboratory first discovered einsteinium in 1952. But einsteinium's instability limited scientists ability to study the element.

Before researchers at Berkeley could test the element's properties, they had to acquire a stable sample. The einsteinium molecules used for these tests were synthesized by the Oak Ridge National Laboratory's High Flux Isotope Reactor.

Using the reactor, scientists blasted atoms of curium, element 96, with neutrons -- triggering a complicated series of nuclear reactions that yielded einsteinium. Unfortunately, their einsteinium sample was thoroughly contaminated with californium.

Researchers were forced to come up with an imaging technique capable of rendering the einsteinium atoms while ignoring the californium atoms.

The team had to work fast, as einsteinium decays extremely quickly. For the tests, researchers used einsteinium-254, one of the element's most stable isotopes.

Unfortunately, the team's efforts were interrupted by the pandemic. When scientists returned after several weeks away from the lab, their einsteinium sample was almost depleted.

Despite the challenges, researchers were able to measure the element's bond distance, an important breakthrough.

"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," Abergel said. "What kind of chemical interaction is this element going to have with other atoms and molecules?"

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By measuring an element's bond distance, researchers can then more precisely model the element's interactions with other atoms and molecules, and begin to characterize the element's behavior.

The researchers were able to use einsteinium's bond distance to better understand the element's relationship with its neighbors on the periodic table.

"By getting this piece of data, we gain a better, broader understanding of how the whole actinide series behaves," said Abergel. "And in that series, we have elements or isotopes that are useful for nuclear power production or radiopharmaceuticals."

By characterizing chemical trends at the end of the periodic table, researchers can get a better sense of what yet-to-be discovered elements -- elements beyond the last rows of the table -- might look like.

"We're really starting to understand a little better what happens toward the end of the periodic table, and the next thing is, you could also envision an einsteinium target for discovering new elements," Abergel said.

Researchers mostly discover new elements by antagonizing heavy, exotic elements like einsteinium. In just the last decade, scientists discovered tennessine by blasting berkelium with neutrons.

If scientists could isolate enough pure einsteinium to use it as a target for the discovery of new elements, it might be possible to isolate the element's "island of stability" -- a theoretical isotope featuring a half-life of days, instead of microseconds.

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