Einsteinium is an element with a famous name that almost no one has heard of.
With 99 protons and 99 electrons, it’s in the dark at the bottom of the periodic table of the chemical elements between California and fermium. It first appeared in the explosive wreckage of the first hydrogen bomb in 1952, and the team of scientists who discovered it gave it a name in honor of Albert Einstein.
To date, scientists know little about it.
Einsteinium is highly radioactive. Since there are no stable versions that do not fall apart within a few years, it does not occur in nature. It can be made in a few specialized nuclear reactors, but only in tiny quantities.
On Wednesday, researchers led by Rebecca J. Abergel, who heads the heavy-element chemistry group at Lawrence Berkeley National Laboratory in California, reported in Nature that they have now identified some of the basic chemical properties of einsteinium.
It was’nt easy. In fact, Dr. Abergel her work as the culmination of “a long series of unfortunate events”.
David L. Clark, a scientist at Los Alamos National Laboratory who was not involved in the research, said the end result was a “tour de force” and part of a renaissance in studying these heavy elements, which have very different properties than lighter ones , more common elements and could be used in novel nuclear reactors or cancer therapies.
“This kind of work has never been done,” said Dr. Clark. “It is state of the art.”
It took me a while to get started.
A few years ago, Dr. Abergel got the chance to get an Einsteinium made at the Oak Ridge National Laboratory in Tennessee – a federal research center that was central to making the uranium used in the first atomic bombs – for not raising money for research in time . She was ready for the next Einsteinium production campaign in 2019.
After she and her colleagues designed the experiments and safety procedures for handling the radioactive element, Oak Ridge informed them that there would be no Einsteinium after all. But then about a week later, Oak Ridge said it could deliver some Einsteinium. “All of a sudden it’s like, ‘Oh, it’s coming,” “recalled Dr. Abergel. “But you only get a third of what you thought.”
That smaller amount was less than 250 nanograms, or 250 billionths of a gram – less than a hundred millionth of an ounce.
Worse, the sample the Berkeley researchers received was heavily contaminated with Einsteinium’s neighbor on the periodic table, California. This foiled their original plans to stack the Einsteinium atoms into a crystal and then shed light on the chemical properties of the element by bombarding it with X-rays before examining the pattern of the bouncing rays.
Instead, they turned to a large molecular structure that essentially acted as a claw to hold an einsteinium atom and bind it in eight places. To study this structure, they had to use another research center in the SLAC National Accelerator Laboratory on the other side of San Francisco Bay. During one of the early preps, a sample was too acidic, which caused a container to fail.
Although no radiation leaked, Dr. Abergel: “Because we rightly have so many security protocols, we were told we had to re-evaluate everything and re-evaluate our techniques.”
Los Alamos National Laboratory, the birthplace of atomic bombs, designed a new container for the Berkeley team. That took a few months and finally Dr. Abergel and her colleagues carry out their experiments.
They studied an Isstein from Einsteinium, which contains 155 neutrons in addition to the 99 protons in its nucleus. This is the second longest version of Einsteinium, with a half-life of 276 days. With each delay, they had less Einsteinium to study. About 7 percent of the Einsteinium atoms disappeared every month.
Then, with the coronavirus pandemic, all laboratories – including those needed to study other aspects of the Einsteinium – were closed. When they started work again, most of the sample was gone. But there was still enough to complete most of the research.
From the experiments at SLAC, they measured the length of the molecular bonds between the einsteinium and the eight atoms in the molecular claw that holds it. The length was 2.38 angstroms. An angstrom is one hundred millionth of a centimeter.
They were expecting 2.42 or 2.43 angstroms, said Korey P. Carter, a professor of chemistry at the University of Iowa and another author of the Nature paper. “A statistically significant difference,” he said.
The emission of light by the Einsteinium also unexpectedly shifted to a shorter wavelength than it was bound in the molecular claw. The researchers expected the wavelength to be longer.
Dr. Abergel said the differences suggested the electrons were moving differently than expected.
This is not surprising. With 99 electrons whizzing around an Einsteinium nucleus, it’s difficult to find a model that accurately describes what is going on. Unlike lighter elements, the large positive charge in Einsteinium and other heavy elements causes electrons to travel at speeds that are a sizable fraction of the speed of light. That is, the implications of Einstein’s theory of special relativity must also be considered.
“The electrons move so fast that chemistry changes because chemistry is all about the behavior of electrons,” said Thomas Albrecht-Schönzart, a professor of chemistry at Florida State University who was not involved in the research . “Almost by definition, you will get strange properties.”
This question will be studied for a long time.
“The problem is that these calculations are very difficult,” said Dr. Albrecht Schönzart.
It is unlikely that Einsteinium itself will find practical use anytime soon. But other heavy elements could be like actinium, which is a bit lighter with 89 protons and 89 electrons. And what scientists are learning about Einsteinium could provide even more insight into these elements. “The similarity in this part of the periodic table teaches us principles of structure and bonding,” said Dr. Clark, the scientist at Los Alamos National Laboratory.
Actinium is already being tested as a cancer treatment. Because the chemistry of heavy elements is not well understood, it is more difficult to design molecules that contain them.
“But if we can understand and master this chemistry at this level of chemical bond making, then we can go for things like cancer treatment,” said Dr. Clark.