Element 117 looks set to claim the highest slot yet on the periodic table, thanks to an experiment in Germany that has independently confirmed its existence. In the process, the team also glimpsed a previously unknown isotope of the element lawrencium, thought to have been produced as 117 decayed.

Most elements heavier than uranium are highly unstable and are hard to find in nature. The heaviest of these can only be made artificially by smashing together lighter elements with the correct atomic number, dictated by the number of protons in an atomic nucleus. Finding increasingly heavier elements could lead to the highly anticipated island of stability, a predicted group of massive but stable atoms.

In 2010, a Russian and US team first made element 117 by firing calcium atoms – which have atomic number 20 – into berkelium, which has atomic number 97. The same group was able to repeat the feat in 2012.

In the latest experiment, Christoph Düllmann at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, and his team created four atoms of 117. The atoms survived for less than a tenth of a second before decaying into lighter elements, which the team traced by looking for signatures of each step in the decay chain.


Lawrencium link

Düllmann’s group was attempting to make element 119, which has never been successfully produced, by shooting titanium (atomic number 22) at berkelium. They are still analysing the data to look for any signs of that superheavy element, and they decided to also try making 117 to ensure their detectors were working as expected.

In addition to confirming 117, the group was able to identify a new link in the decay chain. They saw an isotope of dubnium (atomic number 105) emit an alpha particle – two protons and two neutrons bound together – to produce an isotope of lawrencium (atomic number 103) that’s never been seen before.

Even with this new sighting, element 117 does not yet have an official seat at the periodic table. The decision to add an element rests with a joint working party of the International Union of Pure and Applied Chemistry and the International Union of Pure and Applied Physics. The group requires careful analysis from multiple experiments before it will make the call. The most recent additions were elements 114 and 116, which were announced in 2011 after a three-year review.

But the process to make 117 is difficult to repeat because berkelium is hard to come by. That element is produced in small amounts in nuclear reactors and has a half-life of less than a year, which means it takes years to build up enough for an experiment. “It cannot be bought off the shelf,” says Düllmann.

He hopes his team’s fresh data will be able to seal the deal for element 117. “It is always exciting when a new element joins the periodic table,” he says, though he declined to suggest a name during the wait. “We’ll see.”

Journal reference: Physical Review Letters, DOI: 10.1103/PhysRevLett.112.172501