Seaborgium (Sg)

Glenn Seaborg was the first person who could address a letter to himself using an element symbol, and for nineteen years the only one. He said more than once that having element 106 named after him meant more than the Nobel Prize he had already won — a prize is an event, and an element is permanent. Getting there required IUPAC to write a rule and then abandon it.

A rule invented and withdrawn

In 1994 an IUPAC committee, working through the backlog of unnamed elements, adopted the principle that no element should be named after a living person. It was not a rule that had existed before; it was invented in the course of that deliberation, on the reasoning that naming decisions ought to wait for the perspective of history. Under it, element 106 could not be seaborgium, and the draft assigned the name rutherfordium to that square instead.

The American Chemical Society refused. Its objection had two parts. First, the discoverers' traditional naming right was being overridden by a rule written after the fact. Second, the precedent for naming an element after a living person was arguably already on the table in the form of einsteinium — although that case is genuinely ambiguous, since the discovery was classified until after Einstein's death.

A letter-writing campaign followed, organised by colleagues of Seaborg's, and surveys of working chemists found little appetite for the restriction. IUPAC reversed itself. In the 1997 settlement element 106 became seaborgium, and the living-person prohibition quietly disappeared, which is how element 118 was able to be named for Yuri Oganessian two decades later.

Seaborg lived until 1999, long enough to be photographed pointing at his own square.

Who made it

The 1974 experiment at Berkeley, run by Albert Ghiorso and Michael Nitschke with the Lawrence Livermore group, used a californium target under an oxygen beam and identified seaborgium-263 through its alpha decay chain. Dubna reported element 106 the same year by a different route, detected through spontaneous fission of a short-lived product.

The Transfermium Working Group examined both in 1993 and, unusually for this stretch of the table, did not split the credit. The Berkeley result was judged convincing and the Dubna result was not confirmed by subsequent work. Element 106 is one of the few in this region with a single undisputed discoverer.

Six molecules of carbon monoxide

Seaborgium sits below chromium, molybdenum and tungsten, and the interesting question about any transactinide is whether relativistic effects have wrecked its group behaviour. For element 106, the answer so far is no — which is itself worth knowing, because it is not the answer element 104 or element 105 gave.

Two experiments make the case. In the late 1990s, gas-phase work showed that seaborgium forms a volatile oxychloride and oxyhydroxide with the same stoichiometry and roughly the expected volatility as molybdenum's and tungsten's. Group 6 behaviour, on a handful of atoms.

The second is more striking. In 2014, a team led by Jadambaa Even at Darmstadt produced seaborgium hexacarbonyl — a single seaborgium atom bound to six carbon monoxide molecules — and measured its adsorption behaviour. Chromium, molybdenum and tungsten all form hexacarbonyls; they are standard reagents that a chemistry undergraduate might handle. Element 106 does the same thing.

That result, published in Science, was the first organometallic compound of any superheavy element. It matters because carbonyl bonding depends on the metal donating electron density back into the ligand from d orbitals, so making one proves something specific about seaborgium's electronic structure rather than merely about its size and volatility. It also opened a practical route: carbonyl complexes are volatile at low temperatures, which makes them far easier to transport out of a target chamber than the corrosive halides earlier work relied on.

What survives, and for how long

Around a dozen isotopes are known. Seaborgium-269 lasts a couple of minutes and seaborgium-271 somewhat less; most are gone in seconds. Every chemical result described above was obtained on atoms produced individually, swept out of a target chamber by a gas stream, and detected by their decay a few seconds later — which means each data point is one atom that existed, reacted, and died.