The missing element

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?