Researchers claim discovery of superheavy element “unbibium”

April 29, 2008

An international team of researchers may, just may, have made a radical breakthrough that could rewrite physics and chemistry textbooks.

They claim to have discovered a naturally occurring element with an atomic number (number of protons) of 122 — 30 notches on the periodic table ahead of uranium, long considered the heaviest naturally occurring element.

For decades, physicists have been making artificial elements in supercolliders, only to see most of their creations disintegrate within a short time.

Most elements above atomic number 100 are inherently unstable and get progressively more usntable as you travel upward. The highest discovered one, ununoctium or atomic number 118, has a half-life of 89 milliseconds.

But according to theory, there exists an "island of stability" further out along the periodic table where certain configurations of protons and neutrons would create superheavy but also superstable elements.

So a team led by Amnon Marinov of the Hebrew Univ. of Jerusalem took a different approach. They figured that if superheavy, superstable elements really are possible, then they ought to already exist in nature.

Taking a relatively large amount of thorium, a natural element with the atomic number 90, they fired each and every nucleus in the pile through a mass spectrometer, which catches the atomic weight of nuclei (protons plus neutrons) by analyzing how beams of ions pass through them.

The two isotopes of thorium, with atomic weights of 230 and 232, were most abundant, as were various impurities in the sample.

But there was something else—something with an atomic weight of 292, something never before seen.

The researchers aren't certain, but they figure their unknown substance probably has an atomic number of 122, whose slot on the periodic table already has the temporary name "ununbibium," or "one-two-two-bium."

They also figure its half-life is at least 100 million years—meaning the shores of the long-sought "island of stability" may finally have been reached.

They're ruled out various errors, and are ready to defend their paper, posted Thursday on the math and physics Web site arXiv.org:

Superheavy element found

The hunt for superheavy elements has focused banging various heavy nuclei together and hoping they’ll stick. In this way, physicists have extended the periodic table by manufacturing elements 111, 112, 114, 116 and 118, albeit for vanishingly small instants. Although none of these elements is particularly long lived, they don’t have progressively shorter lives and this is taken as evidence that islands of nuclear stability exist out there and that someday we’ll find stable superheavy elements.

But if these superheavy nuclei are stable, why don’t we find them already on Earth? Turns out we do; they’ve been here all along. The news today is that a group led by Amnon Marinov at the Hebrew University of Jerusalem has found the first naturally occuring superheavy nuclei by sifting through a large pile of the heavy metal thorium.

What they did was fire one thorium nucleus after another through a mass spectrometer to see how heavy each was. Thorium has an atomic number of 90 and occurs mainly in two isotopes with atomic weights of 230 and 232. All these showed up in the measurements along with a various molecular oxides and hydrides that form for technical reasons.

But something else showed up too. An element with a weight of 292 and an atomic number of around 122. That’s an extraordinary claim and quite rightly the team has been diligent in attempting to exclude alternative explanations such as th epresence of exotic molecules formed from impurities in the thorium sample or from the hydrocarbon in oil used in the vacuum pumping equipment). But these have all been ruled out, say Marinov and his buddies.

What they’re left with is the discovery of the first superheavy element, probably number 122.

What do we know about 122? Marinov and co say it has a half life in excess of 100 million years and occurs with an abundance of between 1 and 10 x10^-12, relative to thorium, which is a fairly common element (about as abundant as lead).

Theorists have mapped out the superheavy periodic table and 122 would be a member of the superheavy actinide group. It even has a name: eka-thorium or unbibium. Welcome to our world!

This may well open the flood gates to other similar discoveries. Uranium is the obvious next place to look for superheavy actinides. I’d bet good money that Marinov and his pals are eyeballing the stuff as I write.

The paper, “Evidence for a long-lived superheavy nucleus with atomic mass number A = 292 and atomic number Z @ 122 in natural Th” is available here:

http://arxiv.org/pdf/0804.3869v1

The posting at ArXiv Blog: http://arxivblog.com/?p=385

SOURCES: ArXiv Blog; Fox News