Ununseptium

Ununseptium 

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 original experiment 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 its 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, ununseptium 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.


Discovery of Ununseptium

In 2009, the first atoms of element 117 were made in the Flerov Laboratory of Nuclear Reactions in Dubna, Russia. Evidence of the synthesis was published in April 2010, by scientific teams from Russia and the United States of America.

The research effort, led by Yuri Oganessian, was a collaboration between the Joint Institute of Nuclear Research (Dubna, Russia); the Research Institute for Advanced Reactors, Dimitrovgrad; Lawrence Livermore National Laboratory; Oak Ridge National Laboratory; Vanderbilt University, Tennessee; and the University of Nevada, Las Vegas.

The discovery has not yet been verified by IUPAC. Ununseptium’s place in the periodic table is unofficial until IUPAC validates its existence.

Ununseptium was made by a fusion reaction of element 20 with element 97: calcium-48 with berkelium-249.

Calcium ions were formed into a beam in a cyclotron (a particle accelerator) and fired at a target layer of berkelium deposited 300 nm thick on titanium foil.

The first bombardment lasted 70 days. The berkelium was bombarded with over 7 trillion calcium-48 ions per second, accelerated to about 10% of the speed of light.

The data suggest five nuclei of interest were produced during the 70 day bombardment. As a consequence of the high energy of the impacts that created them, these nuclei instantly lost thermal energy by emitting four neutrons to form ununseptium-293.

The ununseptium-293 (approximate half-life 14 ms) decayed by alpha emission into element 115 (ununpentium).

In a second bombardment lasting 50 days, the speed of the bombarding calcium-48 ions was reduced. The resulting impacts were of lower energy and the single nucleus of interest that formed needed to emit just three neutrons to lose its excess energy, leading to the heavier ununseptium-294 isotope. The data suggest one atom of ununseptium-294 (approximate half-life 78 ms) was formed in the bombardment, decaying again to element 115.

As a result of its position in Group 17 of the periodic table, ununseptium is expected to have chemical properties characteristic of the halogens. The effects of relativistic electrons, however, may result in partial metalloid properties.

Too little of the element has been synthesized for its chemical properties to be confirmed.

Jim Roberto from Oak Ridge said: “New isotopes observed in these experiments continue a trend toward higher lifetimes for increased neutron numbers, providing evidence for the proposed ‘island of stability’ for super-heavy nuclei.”

The joint teams at JINR in Dubna and Lawrence Livermore in California have published evidence for the synthesis of elements 113, 114, 115, 116, 117 and 118.

IUPAC has accepted the discoveries of element 114 (flerovium/ununquadium) and element 116 (livermorium/ununhexium). It has not yet considered the evidence for the discovery of element 117 (ununseptium).

IUPAC requires stronger evidence before it will confirm the synthesis of element 113 (ununtrium), element 115 (ununpentium), or element 118 (ununoctium).

Appearance and Characteristics

Harmful effects:

Ununseptium is harmful due to its radioactivity.

Characteristics:

• Ununseptium is a synthetic radioactive metal and has only been produced in minute amounts.

Uses of Ununseptium

• Ununseptium is of research interest only.