Two fat atoms get the nod

Super-sizing the periodic table

If you’re the kind of person to lay out more than US$8,000 on a periodic table coffee table, The International Union of Pure and Applied Chemistry (IUPAC) has bad news for you: it’s obsolete.

That’s because after deliberations lasting more than a decade, and a review process begun in 2008, the Joint Working Party on the Discovery of Elements of the IUPAC and the International Union of Pure and Applied Physics (IUPAP) has agreed (announcement here, full document here) to add two new elements to the periodic table.

The transfermium elements, with atomic numbers 114 and 116, decay in a few minutes. Tentatively named flerovium (after Soviet physicist Georgy Flyovov) and moscovium (for Moscow Orblast), the elements start their brief existence when curium atoms are bombarded with calcium nuclei. The resulting 116 nuclei last a few milliseconds before decaying into 112 (only accepted last year, and given the name copernicium), passing through 114 for around half a second on the way through.

In some experiments, 114 was created directly by bombarding plutonium atoms with calcium nuclei.

As well as appending a couple of new members to the periodic table, the decision also means bragging rights for the discovery can now be claimed: the Joint Working Party has officially acknowledged a collaboration between American researchers from Lawrence Livermore National Laboratory in California and at Russia’s Joint Institute for Nuclear Research in Dubna.

If you’re thinking of replacing that coffee table, you may do well to wait a few years more. Still in the queue to have their discovery formally acknowledged are elements with atomic numbers 113, 115 and 118.

A key (though not the only) criterion is how the new elements relate to pre-existing known elements. Their decay – for example, from 116 through 114 to the previously-acknowledge copernicium – established that relationship. If similar relationships can be established for the other proposed elements, they’ll get their own shot at immortality.

The same research collaboration claims to have observed each of these in experiments, but according the Joint Working Party, their claims are still considered inconclusive and “have not met the criteria for discovery”. Element 113, for example, has only been observed a few times, has no connection to other known nuclides, and was spotted in “the absence of cross-bombardments”. ®