Hidden Properties of Rare-Earth Element Promethium Revealed

For the first time, researchers have conducted an experimental examination of promethium's chemistry as a lanthanide element. This groundbreaking study was carried out by Alex Ivanov and his team at Oak Ridge National Laboratory in the United States, where this element was initially discovered nearly eight decades ago. 
 
Lanthanides, also known as rare-earth metals found on the sixth row of the periodic table, are renowned for their diverse range of magnetic, optical, and electrical properties. These unique attributes make them integral to various modern technologies. However, despite its widespread utilization, there remains limited knowledge about Promethium’s (a lanthanide with atomic number 61) chemistry since it was first identified in 1945 by Manhattan Project researchers. 
 
Ivanov recounts how scientists from Oak Ridge isolated an unknown radioactive element amidst global recovery from a devastating war. Named after Prometheus from Greek mythology, who stole fire for mankind's use, promethium represents one of humanity’s significant scientific breakthroughs. 
 
Notwithstanding its lower atomic number compared to other lanthanides', understanding promethium's chemical properties has been challenging due to its lack of stable isotopes. Only minute quantities can be obtained synthetically (mainly Prometheum-147 with a half-life span of 2.62 years), extracted tediously and energy-intensively from nuclear reactors. 
 
This scarcity hampers a comprehensive understanding of basic aspects like bonding distance between atoms or the quantity bonded by a central atom when forming molecules or crystal lattices. 
 
However, Ivanov's team leveraged recent technological advancements in isotope separation to address these gaps. They painstakingly harvested Prometheum-147 atoms from plutonium waste solutions and bonded them with specific organic molecules, enabling deeper insights into how Prometheum interacts within solution environments. 
 
Utilizing synchrotron X-ray absorption spectroscopy enabled the observation of a novel chemical complex—molecular structures wherein central Prometheum atoms bond with surrounding organic molecules. 
 
This process allowed nine prometheum-binding oxygen atoms to be observed, facilitating the probing of several fundamental chemical properties. Ivanov explains that they discovered how prometheum bonds with oxygen atoms, measured bond lengths, and compared these findings with those of other lanthanides. 
 
Subsequently, researchers examined a complete set of comparable complexes across all lanthanide elements, enabling them to observe the "lanthanide contraction" phenomenon spanning the entire series for the first time. 
 
Lanthanide contraction refers to decreasing atomic radii as atomic numbers increase due to poor nuclear charge shielding by inner-shell electrons. This effect causes shrinkage in the lanthanide-oxygen bond length. Observations from Ivanov's team indicated this shortening accelerated early in the lanthanide series before slowing down when atomic numbers increased. 
 
These discoveries have significantly filled gaps in understanding promethium's chemistry and could potentially pave the way for future studies exploring wider applications for this element. 
 
Ivanov believes their new knowledge could enhance methods used in separating prometheum from other lanthanides, a crucial step towards advancing sustainable energy systems. Understanding how prometheum bonds within solutions can foster exploration into its potential use within advanced technologies such as pacemakers, spacecraft power sources, and radiopharmaceuticals.