Scientists have succeeded in creating 18 molecules of a seaborgium carbonyl complex, Sg(CO)6. Seaborgium and other transactinides can be created only in particle accelerators, but studies of their chemistry help determine the accuracy of chemical theory and whether an element’s position in the periodic table correctly reflects its reactivity. The properties of transactinides are uncertain because those elements are subject to relativistic effects in which the innermost s orbitals contract, outer d and f orbitals expand, and electron energy levels split as a result of spin-orbit coupling—all affecting an element’s reactivity. A team working at Japan’s RIKEN Nishina Center for Accelerator-Based Science led by Christoph E. Düllmann of Johannes Gutenberg University, Mainz, in Germany, created Sg(CO)6 by bombarding a 248Cm target with 22Ne and then magnetically separating seaborgium and its group 6 neighbors molybdenum and tungsten from other products (Science 2014, DOI: 10.1126/science.1255720). They next treated the metals with carbon monoxide and funneled them to a silica gas chromatography column lined with radiation detectors to identify the species. Sg(CO)6 adsorption to the column was similar to Mo(CO)6 and W(CO)6 adsorption, which the researchers say confirms theoretical predictions.