Protons do not like to stay close to each other for very long. But if you have the right number neatly balanced between enough neutrons, they can only build an atom that will not disintegrate in the blink of an eye.
Theorists have suggested that 114 may be one such ‘magical’ number of protons – but a recent experiment conducted at the GSI Helmholtz Center for Heavy Ion Research in Germany now makes this incredibly unlikely.
In 1998, Russian experiments finally succeeded in building an element with 114 protons in its nucleus. It was later named flerovium after its birthplace, the Flerov Laboratory for Nuclear Reactions of the Joint Institute for Nuclear Research.
The manufacture of mammoth-sized atoms is by no means easy; this is only achieved by starting with heavyweight elements like plutonium and throwing it with slightly smaller ones like calcium until something gets stuck.
By ‘sticks’ we mean ‘breaks long enough to technically pass for an atom’, which for mountain-sized nuclei is rarely more than a fraction of a second. At 112 protons in size, for example, the transuranic element of copernicium has little chance of lasting longer than 280 microseconds.
Atomic nucleons hold each other as an effect of the strong force shared between the trios of sub-atomic quarks of which they are composed.
At the same time, the repulsive nature of positive charges in protons pushes them apart, meaning that the entire structure on the verge of collapse would falter if they got too close to each other. This is why we see some combinations of nucleons, or isotopes, more frequently than others.
Once an atom has a certain size, a number of other factors related to energy and mass weigh, making it harder for the atom to hold itself together, not to be even harder for physicists to measure its properties. do not predict.
Of course, however, physicists are confident that there are islands of stability in the upper parts of the periodic table, where arrangements of protons can form patterns and shapes that enable them to hold on to life a little longer than neighboring elements.
Nihonium, or element 113, for example, has an isotope with a half-life of about 20 seconds.
When the signs of flerovium were first sifted from a rubble of plutonium and calcium more than 20 years ago, it looked like a true keeper. The signature in the given proposed atoms remains stable for as long as 30 seconds before an alpha particle is spit out and breaks up briefly in copernicium.
The excitement was short-lived. In 2009, Berkeley scientists succeeded in recreating two different isotopes of the element. One lasted a tenth of a second. The second hangs longer than a touch and falls apart after half a second.
The odds do not look good for element 114, but physicists are not the types to leave good enough rest. The University of Mainz has thus grown by using upgraded detectors to study dozens of possible meerovium decay events.
Eventually, two were confirmed as bonafide isotopes. One led to an isotope of copernicium which was seen to degrade in a way not previously observed.
In that case, the flerovium decay chain occurred within 2.4 seconds, with alpha particles. The second isotope is gone in 52.6 milliseconds. What is important is that the efficient way in which each of the two isotopes decayed made it clear that 114 was at least not stable.
Just as exciting as a stable furovium could have been, the new findings of an excited state of copernicium provide solid ground for exploring islands of stability higher on the periodic table, giving theorists important information to further model these phenomena. .
“The existence of the state provides another anchor point for the core theory, because it apparently requires an understanding of both forms of coexistence and form transitions for the heaviest elements,” the researchers note in their report.
While we can now exclude 114 except as one of the magic numbers from the periodic table, there are still giants left to kill.
Physicists have yet to create the hypothetical element, tentatively called unbinilium, or element 120. The production of one of the samples requires powerful technology and advanced knowledge of nuclear physics.
There are plans to shift the limits of atomic masses, with RIKEN in Japan making steady progress in its Nishina Center for Accelerator-Based Science, so we may not have to wait long.
Like the explorers of old, researchers are still confident that there are stable islands just over the horizon. We’ll probably see some mirrors along the way.
This research was published in Physical overview letters.