oganesson

oganesson
Name	oganesson
Number	118
Category	unknown chemical properties, but probably a noble gas
Group	18
Appearance	unknown, predicted to be a solid
Atomic mass	[294]
Electron configuration	[Rn] 5f14 6d10 7s2 7p6 (predicted)
Phase at STP	solid (predicted)
Melting point	325 ± 15 K (predicted)
Boiling point	450 ± 10 K (predicted)

oganesson is a synthetic chemical element with the symbol Og and atomic number 118. 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, near Moscow. The element is named in honor of Yuri Oganessian, a pioneering nuclear physicist renowned for his work in superheavy element research. As a member of period 7 and group 18 of the periodic table, it is currently the heaviest element to have been created and occupies the final position in the noble gas series.

Properties

Due to its extremely short half-life and the minuscule amounts produced, the physical properties of oganesson have not been measured directly. Theoretical predictions, however, suggest it may not behave as a typical noble gas. Relativistic effects are expected to be profound, significantly influencing its electron configuration and atomic radius. These effects arise from the high velocities of inner-shell electrons in such a massive atom, as described by Albert Einstein's theory of relativity. Consequently, oganesson is predicted to be a solid at room temperature, unlike the gaseous states of lighter group 18 elements like xenon and radon.

History

The quest to synthesize element 118 followed a series of discoveries of other superheavy elements throughout the late 20th century. The first successful synthesis was claimed in 2002 by scientists from JINR and Lawrence Livermore National Laboratory, led by Yuri Oganessian and Ken Moody. This achievement came after a controversial retraction in 1999 by researchers at the Lawrence Berkeley National Laboratory. The 2002 experiment involved bombarding a target of californium-249 with a beam of calcium-48 ions using a cyclotron at JINR. The discovery was independently confirmed in 2006 by the same collaboration, solidifying its place in the periodic table.

Synthesis and isotopes

Oganesson has no stable isotopes. The only known isotope, oganesson-294, is produced artificially in particle accelerators. The primary synthesis reaction is the fusion of a calcium-48 projectile with a californium-249 target: ²⁴⁹Cf + ⁴⁸Ca → ²⁹⁴Og + 3 ¹n. This process occurs at facilities like the Flerov Laboratory of Nuclear Reactions in Dubna. Oganesson-294 has a half-life of approximately 0.69 milliseconds, decaying via alpha decay into livermorium-290. The search for heavier isotopes, such as the predicted oganesson-295, is an active area of research at laboratories including the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt.

Predicted characteristics

Extensive computational chemistry calculations predict oganesson will exhibit unique characteristics due to extreme relativistic effects. Its electron affinity is expected to be positive, suggesting it may form a stable anion. The ionization energy is predicted to be lower than that of radon, potentially making it more reactive. Furthermore, its van der Waals radius is calculated to be smaller than that of radon, which would result in higher density and stronger interactions between atoms. These properties challenge the traditional definition of a noble gas, as oganesson may display some metallic character or even participate in weak chemical bonding under certain conditions.

Chemical properties

No experimental chemistry of oganesson has been performed, but theoretical studies suggest its chemistry would be extraordinary. While placed in group 18, it may not be chemically inert. Predictions indicate it could form compounds, such as a stable dimer (Og₂) held together by dispersion forces, or even a oxide like oganesson tetroxide (OgO₄), by analogy to xenon tetroxide. Its predicted electronegativity is similar to that of bromine, and it might exhibit oxidation states of 0, +II, and +IV in compounds with highly electronegative elements like fluorine or oxygen, as explored in studies from the Hebrew University of Jerusalem.

Naming

Following confirmation of its discovery, the discoverers at JINR and Lawrence Livermore National Laboratory proposed the name "oganesson" in 2016. This proposal honored Yuri Oganessian, who made seminal contributions to the field of transactinide element research. The name was ratified by the International Union of Pure and Applied Chemistry (IUPAC) in November 2016, alongside the names for elements 113 (nihonium), 115 (moscovium), and 117 (tennessine). The naming followed IUPAC's traditional convention of ending noble gas names with "-on," though it deviated by naming the element after a living scientist, a rare honor previously extended only to seaborgium.

Category:Chemical elements Category:Noble gases Category:Synthetic elements