The Promethium Revolution: How a New Rare Earth Element Will Change Technology

Scientists have discovered elusive properties hidden in promethium, a rare earth element that has remained largely unexplored since its discovery 80 years ago.

This groundbreaking research, published in the journal Naturerepresents a major advance in the study of rare earths and has the potential to rewrite chemistry textbooks.

Promethium’s 80-year scientific journey

The story of promethium 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 minute quantities.

Named after the mythological Titan who sent 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 whole idea was to explore this very rare element to gain new knowledge. “Once we realized that it was discovered at this national laboratory and at the place where we work, we felt an obligation to do this research to maintain the legacy of ORNL,” Ivanov explained.

Unlocking the Secret of Promethium

A research team led by ORNL scientists prepared a chemical complex of promethium that allowed its characterization in solution for the first time.

Through a series of careful experiments, they revealed the secret of this extremely rare lanthanide, whose atomic number is 61.

Ilja Popovs, another co-lead researcher from ORNL, highlighted the challenges we face 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.”

The rare earth elements, especially the lanthanides (elements 57-71 on the periodic table), are key components of many modern technologies, from lasers and permanent magnets to X-ray screens and cancer drugs.

However, the lack of understanding surrounding promethium represents a significant gap in scientific knowledge.

Santa Jansone-Popova, also a co-leader of the study from ORNL, 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 must assume most of its properties. Now we can actually measure some of them,” enthused Jansone-Popová.

A collaborative effort across national laboratories

The success of this research depended 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 different disciplines.

To study the properties of promethium, ORNL scientists bound 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 occurs naturally in the Earth’s crust at any given time. Unlike other rare earth elements, only trace amounts of synthetic promethium are available due to the lack of stable isotopes. ORNL is the sole 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 a range of lanthanides, including promethium.

Lanthanide contraction refers to the phenomenon where elements with atomic numbers between 57 and 71 are smaller than expected, with their ionic radii decreasing as atomic numbers increase.

“From a scientific point of view, it’s really amazing.” I was surprised once we had all the data. The contraction of this chemical bond speeds up along this atomic row, but slows down considerably after promethium,” Ivanov noted.

This is an important milestone in understanding the chemical bonding properties of these elements and their structural changes in the periodic table.

Implications for modern technology

The discovery of the properties of promethium has far-reaching implications for modern technology.

Many rare earth elements, including elements from the lanthanide and actinide series, have applications ranging from cancer diagnosis and treatment to renewable energy technologies and long-life nuclear batteries for deep space exploration.

Jansone-Popova emphasized the importance of this success in separating these valuable elements.

“You can’t use all these lanthanides as a mixture in modern advanced technologies because you have to separate them first,” explained Jansone-Popová.

“That’s where the contraction becomes very important; it basically allows us to separate them, which is still quite a difficult task.”

Promethium ushers in a new era of rare earths

The team’s success paves the way for a new era of rare earth element research.

“Anything we would call a modern marvel of technology would contain these rare earth elements in one form or another. We are adding the missing link,” Popovs concluded.

In summary, this important research on promethium opens a new frontier in rare earth element research.

By unraveling the mystery of this elusive element, the team filled a significant gap in scientific knowledge and set the stage for future discoveries.

The implications of this study reach far beyond basic science, as promethium and other rare earth elements play a key role in modern technologies, from medical applications to renewable energy sources and space exploration.

As scientists continue to build on this breakthrough, we can expect a new era of innovation and progress in chemistry, materials science and more.

The entire study was published in the journal Nature.

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