This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: An international collaboration led by a research group from GSI/FAIR in Darmstadt, Germany, has achieved the first measurement of the chemical stability of a superheavy element compound. The focus was on the hexacarbonyl complex Sg(CO)₆ of seaborgium (Sg, element 106).
The result: The bond between the seaborgium atom and a carbonyl ligand is weaker than expected based on its position in the periodic table. Relativistic effects are the cause. The results are published in the journal Nature.
Superheavy elements (SHE) with atomic numbers from 104 to 118 are artificially produced in nuclear fusion reactions at particle accelerators—at rates of at most a few atoms per day. Their short lifetimes of at most a few seconds make chemical studies very challenging. A primary goal of studying them is to trace the influence of relativistic effects: Because of the high nuclear charge of SHE, electrons near the atomic nucleus are accelerated to velocities approaching the speed of light.
According to Einstein's theory of special relativity, objects moving near the limiting speed of light become heavier. Bohr's model of the atom tells us that this leads to electrons residing closer to the nucleus and becoming more strongly bound. More distant electrons are not subject to relativistic mass increase and are even moved farther away because the more strongly bound electrons better shield the positive nuclear charge.
Both effects lead to changes in the electronic structure of superheavy atoms and thus in the chemical properties of their compounds, compared with their lighter homologs. Comparative studies of similar complexes of homologous elements thus allow researchers to probe the fundamental underpinnings of the periodic table of the elements. "For the first time, we succeeded in measuring the strength of the chemical bond in a compound of a superheavy element, namely that between the central seaborgium atom and a carbon monoxide ligand.
We then compared it to the strength of this bond in the hexacarbonyl of the lighter homolog, tungsten," explains Dr. Alexander Yakushev of GSI/FAIR, spokesperson for the collaboration. "From chromium through molybdenum to tungsten, the bond strength in the hexacarbonyls increases, suggesting that it should be even stronger in seaborgium.
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