Oganesson, element 118, holds the title. It was first created in 2002 by a Russian-American collaboration at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, though it took more than a decade for the discovery to be officially confirmed and the element formally named. In 2016, IUPAC ratified oganesson along with three other newcomers, completing the seventh row of the periodic table. No element with a higher atomic number has been confirmed since, making oganesson the heaviest known element on Earth and one of the strangest substances ever produced.
How Oganesson Was Created
You cannot find oganesson in nature. It exists only because physicists smashed lighter atoms together with enough force to fuse their nuclei into something heavier. The team at JINR, working with scientists at Lawrence Livermore National Laboratory in California, fired beams of calcium-48 ions at a target made of californium-249. When a calcium nucleus and a californium nucleus merged, the resulting compound nucleus occasionally survived long enough to be detected as oganesson-294, an isotope with 118 protons and 176 neutrons.
“Occasionally” is an understatement. The probability of this fusion event succeeding is vanishingly small. Researchers bombarded the target for months, and across multiple experimental campaigns over several years, only a handful of oganesson atoms were ever observed. Each atom decayed within milliseconds, identified not by direct observation but by the characteristic chain of alpha particles it emitted as it broke apart into lighter elements. The entire body of evidence for oganesson’s existence rests on roughly five detected decay chains.
The choice of calcium-48 as a projectile was not arbitrary. This isotope is unusually neutron-rich for its size, which helps the fused nucleus form with enough neutrons to survive a fraction of a second rather than flying apart immediately. The same calcium-48 beam was used to synthesize several other superheavy elements during the 2000s and 2010s, making it one of the most important tools in modern nuclear physics.
The Last Four Elements Named Together
Oganesson did not receive its name alone. In late 2016, IUPAC officially named four elements at once: nihonium (element 113, symbol Nh), moscovium (element 115, symbol Mc), tennessine (element 117, symbol Ts), and oganesson (element 118, symbol Og).1Pure and Applied Chemistry. Names and symbols of the elements with atomic numbers 113, 115, 117 and 118 (IUPAC Recommendations 2016) This was the first time the periodic table’s seventh period was complete, filling every slot from francium (87) through oganesson (118).
The naming process follows a strict protocol. Once a joint IUPAC-IUPAP working group confirms a discovery, the credited team proposes a name and symbol. Elements can be named after a mythological concept, a mineral, a place, a property, or a scientist. The proposal goes through the IUPAC Inorganic Chemistry Division for review and is eventually ratified by the IUPAC Council.2International Union of Pure and Applied Chemistry. How to Name New Chemical Elements The gap between synthesis and naming can stretch over a decade, because confirming that a new element was genuinely produced requires independent replication or extraordinarily convincing evidence from the original lab.
Oganesson was named in honor of Yuri Oganessian, the Russian nuclear physicist who led the research program at JINR responsible for discovering several superheavy elements. He is one of only two people to have an element named after them while still alive, the other being Glenn Seaborg, whose name graces seaborgium (element 106). Nihonium takes its name from the Japanese word for Japan, moscovium from Moscow, and tennessine from the state of Tennessee, home to Oak Ridge National Laboratory.
A Noble Gas That Probably Is Not a Gas
On the periodic table, oganesson sits directly below radon in the noble gas column. You might expect it to behave like other noble gases: colorless, odorless, chemically inert, and gaseous at room temperature. Theoretical calculations suggest it does none of these things.
Relativistic effects on oganesson’s electrons are so extreme that they fundamentally alter its predicted behavior. At element 118, the innermost electrons orbit so close to the massive nucleus that they approach a significant fraction of the speed of light. This changes their energy levels and, through a cascade of knock-on effects, reshapes the entire electron cloud. Computational studies predict that oganesson would be a solid at room temperature, with a melting point around 325 K (roughly 52°C or 125°F). When the same calculations are run without accounting for relativity, the predicted melting point drops to about 220 K, which would make it a gas, as you would expect from a normal noble gas. Relativistic effects shift the melting point upward by roughly 100 degrees.3PubMed Central. Oganesson: A Noble Gas Element That Is Neither Noble Nor a Gas
Its electron cloud may also be unusually diffuse and nearly uniform in density, which would make oganesson chemically reactive rather than inert. Some models suggest it could form compounds with fluorine, something unheard of for lighter noble gases under normal conditions. None of this can be tested experimentally with current technology. Oganesson atoms exist for milliseconds and have been produced only a few at a time, so measuring bulk properties like melting points or chemical reactivity is out of the question for the foreseeable future. Everything known about oganesson’s material properties comes from theory.
Relativistic Weirdness Across the Superheavy Elements
Oganesson is not the only superheavy element where relativity rewrites the rules. Tennessine (element 117), which sits in the halogen group alongside fluorine, chlorine, bromine, iodine, and astatine, also shows pronounced relativistic distortions. Studies of the halogen group find that as atomic number climbs, the inner p orbitals contract under relativistic effects while the outer orbitals shift in complex ways because spin-orbit coupling grows slightly faster than the mass-velocity effect.4Physica Scripta. Relativistic effects on properties of halogen group elements/ions In practical terms, this means tennessine’s ionization energies, electron affinity, and atomic radius do not follow the neat trends established by the lighter halogens. Its chemistry, if it could ever be studied, would likely surprise anyone expecting it to behave like a heavier version of iodine.
This pattern holds throughout the bottom of the periodic table. The heavier an element gets, the less reliably you can predict its properties by looking at the lighter elements above it in the same column. The periodic table’s neat vertical relationships, so useful for the first hundred-odd elements, start to break down precisely because of these relativistic effects. For chemists, this is both fascinating and frustrating: the superheavy elements occupy spots on the table that imply certain behaviors, but the atoms themselves may not cooperate.
Why Scientists Keep Pushing Heavier
The drive to synthesize elements beyond oganesson is not about practical applications. These atoms last fractions of a second and are produced a few at a time. The motivation is more fundamental: reaching the predicted “island of stability.”
Since the 1960s, nuclear physics models have predicted that certain combinations of protons and neutrons form unusually stable configurations, analogous to the “magic numbers” that make certain lighter nuclei especially tightly bound. For superheavy elements, various models predict enhanced stability around proton numbers 114 to 126 and neutron numbers like 172 or 184.5Physica Scripta. Nuclear structure features of very heavy and superheavy nuclei—tracing quantum mechanics towards the ‘island of stability’ The idea gained traction in the 1970s when leading figures like Glenn Seaborg at Berkeley and Georgy Flerov at Dubna took serious interest, building on the nuclear shell model developed by Maria Goeppert Mayer and Hans Jensen.6Philosophical Transactions of the Royal Society A. The transuranic elements and the island of stability
If the island of stability exists as predicted, some superheavy isotopes could survive for seconds, minutes, or conceivably even longer, instead of the milliseconds typical of the heaviest known isotopes. That would open a window for actual chemical experiments, allowing scientists to test whether these atoms really do defy periodic-table expectations as dramatically as theory suggests. The isotopes of oganesson produced so far are neutron-poor relative to the predicted stability peak, so the island’s center has not yet been reached.
The Race for Element 119 and Beyond
Multiple laboratories around the world are actively trying to produce element 119, which would be the first element in the periodic table’s eighth row. The challenge is enormous. The calcium-48 approach that worked so well for elements 114 through 118 has essentially run its course, because there is no suitable target that, when fused with calcium-48, would yield element 119 and survive long enough to detect.
Researchers are exploring heavier projectile beams instead. One promising avenue involves titanium-50 beams fired at targets of californium-251, which could theoretically produce element 120.7Physical Review C. Investigation of the formation of superheavy elements with atomic numbers 116 and 120 through 50Ti-induced reactions Other theoretical studies have investigated manganese-55 projectiles aimed at various actinide targets as pathways to elements 119 through 123, though the predicted production rates are extraordinarily tiny, measured in femtobarns, a unit of cross-section so small that successful collisions might happen only a few times per year of continuous bombardment at best.8Nuclear Analysis. Fusion mechanism involved in the synthesis of superheavy element Z>118 using Mn projectiles
The RIKEN laboratory in Japan, which was credited with discovering nihonium, has been running experiments aimed at element 119 using a vanadium beam on a curium target. JINR in Russia has upgraded its facilities and planned similar campaigns, though international collaborations have been complicated by geopolitical tensions since 2022. Facilities in Germany at GSI Darmstadt and in the United States are also in the conversation. Whoever confirms element 119 first will earn naming rights and a place in scientific history.
The Target Problem
One of the least glamorous but most critical bottlenecks in superheavy element research is the target material itself. To make elements heavier than oganesson, you typically need targets made of rare actinides like berkelium, californium, or einsteinium. These materials do not occur naturally. They can only be produced through intense neutron irradiation in very high flux nuclear reactors, followed by chemical processing and purification in specialized hot cell facilities that exist in only a handful of locations worldwide.9The European Physical Journal A. Actinide targets for the synthesis of superheavy nuclei
The berkelium-249 target used to discover tennessine, for example, required a dedicated production campaign at Oak Ridge National Laboratory’s High Flux Isotope Reactor. The material took over a year to accumulate, and once removed from the reactor it began decaying (berkelium-249 has a half-life of about 330 days), giving the experimenters a limited window to use it. Producing enough target material for future experiments is a recurring challenge that limits how quickly new elements can be attempted. It is not just a matter of building a better accelerator; you need the right atoms to shoot at, and those atoms are among the rarest materials on the planet.
Where the Periodic Table Might End
There is no consensus on exactly where the periodic table stops being meaningful. From a nuclear physics standpoint, the question is when nuclei become so unstable that they cannot exist even briefly. From an atomic physics standpoint, the question is when the electron structure around a nucleus ceases to behave in a way that resembles chemistry at all.
Fundamental difficulties emerge from quantum electrodynamics. As nuclear charge increases, the innermost electron energy levels are predicted to eventually merge with the negative-energy continuum. Beyond a certain charge, this could lead to spontaneous electron-positron pair creation, meaning the vacuum around the nucleus starts producing matter and antimatter. At that point, the very concept of a stable atomic structure becomes questionable.10Nature Reviews Physics. The quest for superheavy elements and the limit of the periodic table Estimates for this threshold vary, but many place it somewhere around element 170 to 175, though some argue the practical limit is much lower because nuclear instability kills the atoms long before the electron structure becomes exotic enough to be a problem.
For the foreseeable future, though, the limit is practical rather than theoretical. Making elements 119 or 120 is already at the edge of current technology. Each step higher in atomic number roughly halves (or worse) the already minuscule production probability. If element 119 is confirmed in the next decade, that will be considered a major triumph. Reaching element 126, the proton magic number some models place at the heart of the island of stability, remains a distant aspiration.
Superheavy Elements and Stellar Explosions
Laboratories are not the only places where superheavy nuclei might form. In astrophysics, the rapid neutron capture process (the r-process) that occurs during neutron star mergers and certain types of supernovae builds heavy elements by piling neutrons onto seed nuclei faster than the nuclei can decay. This process is responsible for roughly half of all elements heavier than iron found in nature, including gold, platinum, and uranium.
On its way to building the heaviest naturally occurring actinides, the r-process must necessarily pass through superheavy nuclear territory, synthesizing nuclei with extreme proton and neutron numbers far from anything accessible in laboratory experiments.11The European Physical Journal A. Nucleosynthesis and observation of the heaviest elements Whether any of these astrophysically produced superheavy nuclei survive long enough to affect the observable properties of a neutron star merger, or whether they all decay instantly into lighter elements, remains an open question. If the island of stability is real and robust enough, some superheavy isotopes produced in such events might persist long enough to leave detectable signatures in the material ejected by the explosion. Identifying those signatures would be a way to confirm the island’s existence without needing to build it atom by atom on Earth.
The connection between laboratory synthesis and astrophysical nucleosynthesis runs both ways. Data from superheavy element experiments help refine the nuclear models used to simulate r-process yields, while observations of heavy element abundances in old stars and kilonova remnants provide indirect constraints on the stability of nuclei that no accelerator can yet produce. It is one of those areas where subatomic physics and astronomy are quietly working on the same puzzle from opposite ends.