Tennessine

Ununseptium (Template:PronEng or /ˌʌnənˈsɛptiəm/) is the temporary name of an undiscovered chemical element in the periodic table that has the temporary symbol Uus and has the atomic number 117. It is expected to decay by alpha decay to element 115.

Future experiments

Ununseptium has not yet been discovered. As of March 2008, no attempt to synthesise this element has been reported. The Joint Institute for Nuclear Research in Dubna, Russia, has plans to attempt the synthesis of ununseptium in September 2008. The proposed reaction is:

$\,_{22}^{50}\mathrm {Ti} +\,_{95}^{243}\mathrm {Am} \to \,_{115}^{293}\mathrm {Uus} ^{*}\to \,^{290,289}\mathrm {Uus} .$

Another possible reaction is:

$\,_{20}^{48}\mathrm {Ca} +\,_{97}^{249}\mathrm {Bk} \to \,_{115}^{297}\mathrm {Uus} ^{*}\to \,^{294,293}\mathrm {Uus} .$

Theoretical calculations in a quantum tunneling model with mass estimates from a macroscopic-microscopic model predict the alpha-decay half-lives of isotopes of the element 117 (namely, ^289-303117) to be around 0.1-40 ms.

Electronic structure

Ununseptium would have 6 full shells, 7s+5p+4d+2f=18 full subshells, and 117 orbitals:

Bohr model: 2, 8, 18, 32, 32, 18, 7

Quantum mechanical model: 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰ 4p⁶5s²4d¹⁰5p⁶6s²4f¹⁴5d¹⁰ 6p⁶7s²5f¹⁴6d¹⁰7p⁵

Chemical properties

Certain chemical properties, such as bond lengths, are predicted to differ from what one would expect based on periodic trends from the lighter halogens (because of relativistic effects). Ununseptium may show semimetal properties as well.

Naming

The element with Z=117 is historically known as eka-astatine. The name ununseptium is a systematic element name, used as a placeholder until it is confirmed by other research groups and the IUPAC decides on a name. According to IUPAC rules, names used for previous elements that have ultimately not been adopted are not allowed to be proposed for future use.

External links

• WebElements.com: Uus