Using an unprecedentedly small sample, scientists have taken the first fundamental measurements of the highly radioactive element einsteinium. The results were published on February 3 in the journal Nature.
Einsteinium was first created in 1952 in the aftermath of the first hydrogen bomb test on the island of Elugelab, which is now a part of the Marshall Islands in the Pacific Ocean. But the element’s most common form, on the rare occasions that it is produced, degrades by half every 20 days. Because of the element’s instability and the inherent dangers of studying a super radioactive element, the last attempts to measure einsteinium were in the 1970s, Harry Baker reports for Live Science. The new research not only sheds light on einsteinium and other very heavy elements, but also gives future chemists a model for conducting research on vanishingly small samples.
"It is a very small amount of material. You can't see it, and the only way you can tell it is there is from its radioactive signal,” says University of Iowa chemist Korey Carter, a co-author on the research, to Live Science.
The researchers worked with a slightly more stable version of einsteinium that takes 276 days to lose half its material. Every month, the sample lost about seven percent of its mass. To protect the sample—and the researchers—from its radioactive decay, the team created a 3-D-printed sample holder for the task.
“There were questions of, ‘Is the sample going to survive?’ that we could prepare for as best as we possibly could,” says Carter to Gizmodo’s Isaac Schultz. “Amazingly, amazingly, it worked.”
Einsteinium sits at the very bottom of the periodic table, in a row of heavy elements called called the actinides among neighbors like uranium and plutonium. All actinides are highly radioactive and most aren’t found in nature. When atoms get very big, like actinides are, it becomes difficult for chemists to predict how they’ll behave because they have so many sub-atomic particles with opposing charges that are barely held together.
For example, the particles around the outside of an atom are the negatively charged electrons, and the outermost electrons are called valence electrons. The number of valence electrons that an atom has determines how many other atoms it can form bonds with. Because einsteinium is so big, it’s hard to predict its valence value, but in the new paper, the researchers were able to measure it.
“This quantity is of fundamental importance in chemistry, determining the shape and size of the building blocks from which the universe is made,” writes Keele University chemist Robert Jackson in the Conversation. “Einsteinium happens to lie at an ambiguous position on the periodic table, between valence numbers, so establishing its valence helps us understand more about how the periodic table should be organized.”
The team got their einsteinium from the Oak Ridge National Laboratory’s High Flux Isotope Reactor. Normally, the Oak Ridge reactor makes californium, which is useful for things like detecting gold and silver ore. Californium and einsteinium have a lot in common, so the latter is often a byproduct of californium production. It’s tough to separate them, which is why the lab only got a very small sample of einsteinium—about 200 billionths of a gram—and even then, it was too contaminated with californium to conduct some of their tests.
The team bombarded a some of their einsteinium with high-energy light using the Stanford Synchrotron Radiation Lightsource in order to take measurements. In one result, the team found that while most actinides reflect a longer wavelength than the light shot at them, einsteinium does the opposite, and reflects shorter wavelengths. The team also found that when other elements bonded to einsteinium, the bonds were slightly shorter than they’d predicted.
“That tells us that there is something special about einsteinium, in that it doesn’t behave as we expected,” says lead author Rebecca Abergel, a chemist at the University of California, Berkeley’s, to Shamini Bundell and Nick Howe at Nature News.