Scientists at Berkeley Lab have used a titanium beam to make atoms of element 116. Not only does this represent a new way to make the super rare element, but it stands as a proof-of-concept that they could soon potentially create the as-yet-undiscovered element 120, which may be stable.
The periodic table arranges elements based on their atomic number, or the number of protons each element has in its nucleus. While the first 94 elements on the chart are all found in nature, any heavier than that have only been created in the lab, by fusing existing elements together.
On paper, it sounds relatively simple: if you want an element of a specific atomic number, just smash together two other elements that have a combined total of that many protons. So for instance, to make the element oganesson, which has 118 protons, scientists usually fire a beam of calcium (with 20 protons) at a target made of californium (with 98 protons).
Firing a calcium beam at different targets is how the superheavy elements 112 to 118 were first synthesized. It’s expected that more elements lay beyond the edge of the periodic table, but unfortunately californium is the heaviest element that can be used as a target – the next ones up are too unstable.
So if you can’t change the target, change the projectile. That’s what the Berkeley Lab team has now done, getting the extra two protons by upping the beam from calcium to titanium, which has 22 protons. Doing so isn’t as easy as it sounds though.
First, the process requires titanium-50, a rare isotope that only makes up around 5% of all natural titanium on Earth. This is then heated in a specialized oven that cranks it up to almost 3,000 °F (1,649 °C), vaporizing the titanium. An ion source produces a plasma of charged titanium, which can then be manipulated into a beam and fired at the target.
This is the first time a titanium beam has been used in experiments like this, so to test that it was working, the team fired it at a target made of plutonium, which has 94 protons. That results in production of element 116, livermorium. And sure enough, the team detected the elusive element, albeit very rarely: only two atoms of the stuff were produced over a 22-day experiment.
With this proof-of-concept in place, the team now plans to use the titanium beam to hunt for the hypothesized element 120. This could be done by firing titanium at a californium target – although it’s expected to be an even rarer occurrence.
“We think it will take about 10 times longer to make 120 than 116,” said Reiner Kruecken, director of Berkeley Lab’s Nuclear Science Division. “It’s not easy, but it seems feasible now.”
If it was to be discovered, element 120 (or Unbinilium, to use its placeholder name) is predicted to be an alkaline earth metal and would sit in the currently-empty eighth row of the periodic table, alongside the also-undiscovered element 119.
But most excitingly, element 120 has a good chance of being on the “island of stability.” Superheavy elements usually have very short half-lives, meaning they decay away in a matter of milliseconds, which makes them difficult to study and impractical for basically any real-world use. But it’s been predicted that some isotopes of these elements might have just the right number of neutrons to balance the whole thing out, stabilizing it for minutes or even days. If so, element 120 could therefore be the most useful new element created in quite some time.
The researchers could get started with the experiments as early as 2025, although it could still take a few years to produce any atoms of element 120.
The research has been submitted to the journal Physical Review Letters.
