Scientists have discovered the elusive properties hidden in promethium, a rare earth element that has remained largely unexplored since its discovery 80 years ago.
This historic research, published in the journal Naturemarks a significant advance in rare earth studies and could potentially rewrite chemistry textbooks.
The scientific journey of Promethium, 80 years
The Promethium story began in 1945 at Oak Ridge National Laboratory (ORNL), formerly known as Clinton Laboratories. It was here that the element was first discovered and continues to be produced in trace quantities.
Named after the mythological Titan who delivered fire to humans, promethium symbolizes the human quest for knowledge and understanding.
Alex Ivanov, an ORNL scientist who co-led the research, expressed the team’s sense of obligation to preserve the lab’s legacy.
“The idea was to explore this very rare element to acquire new knowledge. Once we realized that it was discovered in this national laboratory and in the place where we work, we felt compelled to conduct this research to preserve the legacy of ORNL,” Ivanov explained.
Unraveling the mysteries of promethium
The research team, led by ORNL scientists, prepared a chemical complex of promethium, enabling its characterization in solution for the first time.
Through a series of careful experiments, they revealed the secrets of this extremely rare lanthanide, whose atomic number is 61.
Ilja Popovs, another co-leader of research at ORNL, highlighted the challenges faced in studying promethium, saying: “Because it has no stable isotopes, promethium was the last lanthanide to be discovered and was the most difficult to study. »
Rare earth elements, particularly lanthanides (elements 57 to 71 of the periodic table), are essential components of many modern technologies, from lasers and permanent magnets to X-ray screens and cancer drugs.
However, the lack of understanding of promethium represents a significant gap in scientific knowledge.
Santa Jansone-Popova, also co-leader of the ORNL study, emphasized the importance of this research.
“There are thousands of publications on lanthanide chemistry without promethium. This was a glaring gap for all of science. Scientists have to assume most of its properties. We can now measure some of them,” enthuses Jansone-Popova.
Collaborative effort between national laboratories
The success of this research relied on the unique resources and expertise available at DOE national laboratories.
The team used a research reactor, hot cells and supercomputers, as well as the accumulated knowledge and skills of 18 scientists from various fields.
To study the properties of promethium, ORNL scientists linked radioactive promethium-147 to special organic molecules called diglycolamide ligands.
Using X-ray spectroscopy, they determined the chemical bond length of promethium with neighboring atoms, a first for science and a long-missing piece of the periodic table puzzle.
Promethium is incredibly rare; only about a pound is naturally present in the earth’s crust at any given time. Unlike other rare earth elements, only trace amounts of synthetic promethium are available due to its lack of stable isotopes. ORNL is the only producer of promethium-147 in the United States.
Understanding lanthanide contraction
One of the most significant findings of this study was the first demonstration of lanthanide contraction in solution for the entire lanthanide series, including promethium.
Lanthanide contraction refers to the phenomenon in which elements with atomic numbers between 57 and 71 are smaller than expected, with their ionic radii decreasing as their atomic number increases.
“It’s really astonishing from a scientific point of view. I was struck once we had all the data. The contraction of this chemical bond accelerates along this atomic series, but after promethium it slows down significantly,” Ivanov noted.
This is an important step in understanding the chemical bonding properties of these elements and their structural changes throughout the periodic table.
Implications for modern technology
The discovery of promethium’s properties has far-reaching implications for modern technology.
Many rare earth elements, including those in the lanthanide and actinide series, have applications ranging from cancer diagnosis and treatment to renewable energy technologies and long-lived nuclear batteries for energy exploration. deep space.
Jansone-Popova emphasized the importance of this achievement in separating these precious elements.
“You can’t use all these lanthanides as a mixture in modern cutting-edge technologies, because you have to separate them first,” Jansone-Popova explained.
“This is where the contraction becomes very important; this essentially allows us to separate them, which is still quite a difficult task.
Promethium ushers in a new era of rare earths
The team’s achievements pave the way for a new era of rare earth element research.
“Anything we would call a modern technological marvel would include, in some form, these rare earth elements. We add the missing link,” concluded Popovs.
In summary, this important research on promethium opens a new frontier in the exploration of rare earth elements.
By revealing the secrets of this elusive element, the team has filled a significant gap in scientific knowledge and paved the way for future discoveries.
The implications of this study extend far beyond the realm of basic science, as promethium and other rare earth elements play crucial roles in modern technologies, from medical applications to renewable energy and space exploration.
As scientists continue to build on this historic achievement, we can expect to see a new era of innovation and advancement in chemistry, materials science and beyond.
The full study was published in the journal Nature.
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