Seaborgium Hexacarbonyl Shows Relativistic Bond Weakening

Researchers have observed relativistic bond weakening in seaborgium hexacarbonyl, a compound formed by the superheavy element seaborgium. This phenomenon was identified through gas chromatography analysis of the compound's behavior. The study, published online on October 7, 2026, in the journal Nature, specifically examined the hexacarbonyl complex of seaborgium, denoted as Sg(CO)6. The analysis demonstrated that Sg(CO)6 exhibits a lower first bond dissociation energy when compared to its lighter chemical homologue, tungsten hexacarbonyl (W(CO)6).

Bond dissociation energy is a measure of the strength of a chemical bond, indicating the amount of energy required to break that bond. A lower bond dissociation energy signifies a weaker bond. The findings suggest that the presence of relativistic effects significantly influences the chemical properties of superheavy elements like seaborgium. Relativistic effects become pronounced for elements with high atomic numbers, where the inner electrons orbit the nucleus at speeds approaching a significant fraction of the speed of light. These high speeds cause the electrons to experience mass increase, leading to a contraction of their orbitals and a subsequent alteration of the atom's chemical behavior, including the strength of its bonds with other atoms or molecules.

The comparison with tungsten hexacarbonyl (W(CO)6) is crucial because tungsten is in the same group (Group 6) of the periodic table as seaborgium, making it a chemical analogue. By comparing the bond dissociation energies of Sg(CO)6 and W(CO)6, scientists can isolate and quantify the impact of relativistic effects on seaborgium's bonding. The observation of a lower first bond dissociation energy in Sg(CO)6 directly supports the theory that relativistic effects are weakening the bonds within this superheavy element compound.

This research contributes to the broader understanding of the chemistry of superheavy elements, which often deviate from the trends predicted by non-relativistic quantum chemistry. The study's methodology, employing gas chromatography, allowed for the precise measurement of the compound's properties under controlled conditions. The implications of this finding extend to theoretical chemistry, providing experimental validation for models that incorporate relativistic quantum mechanics to describe the behavior of elements at the extreme end of the periodic table. Further research may explore other seaborgium compounds or complexes of other superheavy elements to ascertain the universality and extent of these relativistic bond weakening effects.