A new element on the Table
In April an international team of scientists, led by Yuri Oganessian of the Russian JINR (Joint Institute for Nuclear Research) at Dubna believes it has synthesised element 117, Ununseptium (Uus), filling the gap in the row of actinides and transactinides in the Periodic Table.
Reporting their findings in a recent issue of Physical Review Letters (2010, 104, 142502), the researchers bombarded a target of 249Bk with the neutron-rich isotope 48Ca for 140 days, synthesising five atoms of 293117 and one atom of 294117, with lifetimes ca 21 and 112 ms, respectively.
24997Bk + 4820Ca → 293117 + 4 10n
24997Bk + 4820Ca → 294117 + 3 10n
The team found that element 293117 had undergone a series of three α-decays via elements 115 and 113 to 281Rg, while decay of the more stable 294117 was traced through six -decays to 270Db. The researchers also observed long lifetimes for 274Bh and 270Db, at 1.3 m and 33.4 h, respectively.
Before the discovery can be ratified, however, the synthesis will need to be reproduced by an independent team of researchers. Only once this has been done can a name given to element 117 (as has recently been done for Copernicum, element 112). Likewise, more stable isotopes are needed before chemical experiments can be done to establish how element 117 is related to those elements around it in the Periodic Table, especially the halogens above. Could it be a metallic halogen?