Oganesson

In June 1999 a group at the Lawrence Berkeley National Laboratory announced in Physical Review Letters that they had made elements 118 and 116 by firing krypton-86 at a lead target. The reaction had been predicted to have an unexpectedly high yield, the result was consistent with that prediction, and it was accepted.

Nobody could reproduce it. Berkeley itself could not reproduce it on repeat runs; neither could GSI in Darmstadt nor RIKEN in Japan. In July 2001 the authors published a retraction. A subsequent internal investigation found that the decay chains had not been present in the raw data at all and had been inserted during analysis. The principal author, Victor Ninov, was dismissed in 2002. He denied wrongdoing.

The case is worth recording precisely because superheavy element work is the kind of science in which fabrication is hardest to catch: the events are single atoms, the analysis is a search for rare patterns in a very large dataset, and the number of people able to check is small. What caught it was replication, which is the only thing that ever does.

It caused real damage beyond the retraction. Berkeley had proposed the name ghiorsium for element 118, after Albert Ghiorso; that was withdrawn along with the claim. And the episode remains a standing reason for the caution the international commission now applies to superheavy claims, including its rejection of both competing bids for element 113 in 2011.

The genuine synthesis was carried out at the Joint Institute for Nuclear Research at Dubna, by a Russian and American collaboration with Lawrence Livermore, firing calcium-48 ions at a californium-249 target. The first event was recorded in 2002. The team held the announcement until a confirming experiment in 2005, because the decay energies were uncomfortably close to those of a known contaminant, and published in October 2006, reporting three and possibly four nuclei of oganesson-294.

The international commission recognised the discovery in December 2015, and the name was approved on 28 November 2016, honouring Yuri Oganessian, who had led superheavy element research at Dubna for decades. He was alive at the time, making this the second element after seaborgium to be named for a living person.

Fewer than ten atoms of oganesson have ever been confirmed. Each survives something under a millisecond before alpha decay. There is no sample, there never will be a sample at this half-life, and every statement about its properties beyond its mass and its decay mode is calculation rather than measurement.

The calculations are interesting. Oganesson sits below radon in the noble gas column, but relativistic effects on its electrons are expected to be severe enough that it would not behave like one. Its electron structure is predicted to be smeared rather than sharply shelled, its polarisability high, and the consensus of the theoretical work is that at room temperature it would be a solid rather than a gas, and reasonably reactive. A noble gas that is neither noble nor a gas.

It completes period seven. Element 119 and beyond would begin an eighth, and attempts at 119 and 120 have been running for years without a confirmed result; the calcium-48 route that produced everything from 114 to 118 has no usable target beyond einsteinium and fermium, which cannot be made in the quantities required. Whether the table continues at all is currently a question of accelerator engineering.

There is nothing traditional here, and there cannot be. This element did not exist anywhere in the universe, so far as is known, until it was made in a Russian laboratory in 2002.