Oganesson, designated by the symbol Og, is the heaviest element currently known on the periodic table. This element represents the limit of what physicists and chemists have been able to synthesize, possessing the highest atomic number of any confirmed substance. It is a man-made, superheavy element that is inherently radioactive and highly unstable. Oganesson exists only fleetingly, having never been found in nature, and is solely produced in highly specialized laboratory environments. Its creation and study push the boundaries of nuclear science and atomic theory.
Identity and Naming
Oganesson possesses the atomic number 118, meaning a single atom contains 118 protons in its nucleus. Its position places it in Group 18, the column of elements known as the noble gases, and it completes the seventh period of the periodic table. The element was officially named in 2016, following the recognition of its discovery by the international scientific bodies, IUPAC and IUPAP, in 2015.
The name “oganesson” honors Russian nuclear physicist Professor Yuri Oganessian. This naming convention recognizes a scientist’s pioneering contributions to the field of superheavy elements. Oganessian is recognized for his significant role in the research and discovery of many of the heaviest elements. This naming made Oganessian only the second person to have an element named after them while still alive.
Synthesis of Element 118
The creation of Oganesson relies on a technique known as cold fusion, which requires immense precision and power within a particle accelerator. The process requires bombarding a target of one heavy isotope with a beam of another, lighter isotope to force their nuclei to fuse. The specific reaction that produced Oganesson involved firing a beam of Calcium-48 ions at a target composed of Californium-249.
Calcium-48 was chosen because its nucleus is relatively neutron-rich and stable, which increases the possibility of a successful, albeit rare, fusion event. The Californium-249 target material was deposited onto titanium foil for the bombardment. The collision of the Calcium and Californium nuclei resulted in a fusion product, Oganesson-294, plus the release of three free neutrons.
The first genuine observation of Oganesson occurred in 2002 at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia. This successful synthesis was the result of a long-standing collaboration between the JINR and the Lawrence Livermore National Laboratory (LLNL) in the United States. The experiments were extremely challenging, requiring a beam dose of \(2.5 \times 10^{19}\) calcium ions over a period of many months to produce just a few atoms. Only a handful of Oganesson atoms have ever been detected, underscoring the difficulty and rarity of its synthesis.
Predicted Properties and Relativistic Effects
Because only a few atoms of Oganesson have been produced and their existence is brief, scientists cannot directly measure its physical or chemical properties. Consequently, most of what is understood about Oganesson is derived from advanced quantum mechanical calculations and theoretical models. Its most stable known isotope, Oganesson-294 (Og-294), has an extremely short half-life, decaying in less than a millisecond, with values reported around 0.7 to 0.89 milliseconds. This rapid decay makes experimental study virtually impossible.
The sheer size of the Oganesson nucleus, with its enormous positive charge, causes relativistic effects to dramatically alter the behavior of its electrons. As the inner-shell electrons accelerate to speeds approaching the speed of light, their mass increases, causing the electron shells to contract. This relativistic effect is expected to significantly change the element’s chemistry, making it diverge from the predictable trends of the lighter noble gases.
For instance, while all other Group 18 elements are gases at standard temperature and pressure, Oganesson is predicted to be a solid or a liquid. Theoretical models also suggest that Oganesson may not be truly unreactive, unlike its counterparts, and may even exhibit a metallic or semiconductor nature. This is due to the relativistic effects causing a loss of the distinct shell structure, potentially allowing its outermost electrons to participate in chemical bonding. The study of Oganesson primarily serves to test the accuracy of these theoretical models, providing insights into the fundamental physics of superheavy elements.