Ununseptium

General properties
Name, symbol, number	ununseptium, Uus, 117
Element category	unknown
Group, period, block	17, 7, p
Standard atomic weight	(294)
Electron configuration	[Rn] 5f14 6d10 7s2 7p5 (predicted) 2, 8, 18, 32, 32, 18, 7 (predicted)
History
Discovery	Joint Institute for Nuclear Research and Lawrence Livermore National Laboratory (2010)

Ununseptium is the superheavy artificial chemical element with temporary symbol Uus and atomic number 117. The element, also known as eka-astatine or simply element 117, is the second-heaviest of all the elements that have been reportedly created so far and is the second-to-last element of the 7th period of the periodic table. Its discovery was first announced in 2010—synthesis was claimed in Dubna, Russia, by a joint Russian–American collaboration, thus making it the most recently discovered element. Another experiment in 2011 created one of its daughter isotopes directly, partially confirming the results of the discovery experiment, and the same experiment that was reportedly used to first synthesize the element was repeated successfully in 2012. However, the IUPAC/IUPAP Joint Working Party (JWP), which is in charge of examining claims of discovery of superheavy elements, has made no comment yet on whether the element can be recognized as discovered. Once it is so recognized, it may receive a permanent name which will be suggested for the element by the discoverers; "ununseptium" is a temporary systematic element name that is intended to be used before a permanent one is established. However, it is commonly called "element 117" by researchers and in the literature instead of "ununseptium".

In the periodic table, ununseptium is located in group 17, all previous members of which are halogens. However, the element is likely to have significantly different properties from the halogens, although a few key properties such as the melting and boiling points, as well as the first ionization energy are expected to follow the periodic trends. While scientists agree that lighter ununseptium isotopes are very unstable, there are signs that some heavier ununseptium isotopes may be much more stable.

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