What is "ununoctium"

n. The systematic element name for the chemical element with atomic number 118 (''symbol'' Uuo).

Ununoctium ( symbol Uuo) is the temporary name of a transactinide chemical element. It was first synthesized in 2002 by a joint team of Russian and American scientists at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia. With the atomic number 118 in the periodic table, the synthetic element is also known as element 118, or eka-radon. In December 2015, it was recognized as one of four new elements by the Joint Working Party of international scientific bodies IUPAC and IUPAP. In June 2016, the IUPAC suggested the element to be named oganesson (element symbol: Og), a name expected to be formally accepted by the end of 2016. The proposal is in line with the tradition of honoring a scientist and recognizes nuclear physicist Yuri Oganessian, who has played a leading role in the discovery of the heaviest elements in the periodic table.

Ununoctium has the highest atomic number and highest atomic mass of all known elements. The radioactive ununoctium atom is very unstable, and since 2005, only three or possibly four atoms of the isotope Uuo have been detected. Although this allowed very little experimental characterization of its properties and possible compounds, theoretical calculations have resulted in many predictions, including some surprising ones. For example, although ununoctium is a member of group 18 – the first synthetic one to be so – it may possibly not be a noble gas, unlike all the other elements of that group. It was formerly thought to be a gas under normal conditions but is now predicted to be a solid due to relativistic effects. On the periodic table of the elements it is a p-block element and the last one of the 7th period.