Synthetic elements are chemical elements that do not occur naturally on Earth in any stable or long-lasting form and instead must be created through nuclear reactions in laboratories or reactors. Of the 118 confirmed elements on the periodic table, roughly 26 are considered synthetic, meaning every atom of these elements that has ever been studied was deliberately manufactured by humans. The methods used to create them range from bombarding heavy metals with neutrons inside nuclear reactors to smashing atomic nuclei together at enormous speeds in particle accelerators, and the techniques have grown dramatically more sophisticated since the first synthetic element, technetium, was produced in 1937.
Two Main Routes to Making New Elements
There are fundamentally two ways to build an atom that does not exist in nature. The first is neutron capture in a nuclear reactor, where an existing heavy nucleus absorbs one or more neutrons and then undergoes radioactive decay to become a different element. This is how plutonium was first produced in meaningful quantities: uranium-238 absorbs a neutron, becomes uranium-239, and then decays through a chain of steps into plutonium-239.1Research Starter. Man-Made Elements Reactor-based production works well for elements just a few steps heavier than uranium, like neptunium, plutonium, americium, and curium, because the process can run continuously and generate usable quantities of material.
The second method is ion-beam fusion, sometimes called “atom smashing.” A particle accelerator hurls a beam of lighter nuclei at a target made of a heavier element. If two nuclei collide with just the right energy, they can temporarily merge into a single, heavier nucleus. This approach is the only way to reach the truly superheavy elements, those beyond about element 100 on the periodic table, because reactor-based neutron capture cannot pile on enough protons to get there. The catch is that ion-beam fusion is staggeringly inefficient. Two nuclei that collide usually just bounce apart or shatter. The fraction that actually fuse and survive long enough to be detected can be vanishingly small.
Hot Fusion and the Role of Actinide Targets
The biggest leap in superheavy element discovery came from a technique called hot fusion. In hot fusion experiments, a beam of calcium-48 ions is fired at targets made from heavy actinide elements like plutonium, americium, curium, berkelium, or californium. Since 2000, this approach has led to the discovery of five new elements and more than 50 new isotopes, effectively filling in the bottom row of the periodic table through element 118.2The European Physical Journal A. Actinide targets for the synthesis of superheavy nuclei An earlier accounting of this work confirmed that elements 113 through 118 were all synthesized using calcium-48 beams on actinide targets.3Nuclear Physics A. Actinide targets for the synthesis of super-heavy elements
Calcium-48 turned out to be a remarkably good projectile because it has a large neutron excess relative to its number of protons, which helps the newly formed superheavy nucleus survive the instant after fusion. The target materials themselves are another bottleneck. Elements like berkelium-249 and californium-249 can only be produced through intense neutron irradiation in specialized high-flux reactors, followed by chemical processing in hot cell facilities that exist in only a handful of locations worldwide.2The European Physical Journal A. Actinide targets for the synthesis of superheavy nuclei Producing even a few milligrams of berkelium for a single experiment can take years of reactor time. This scarcity shapes which experiments are even possible.
How Scientists Know They Created a New Element
When an experiment produces just one or two atoms of a new element that exist for less than a second, detecting them is an extraordinary challenge. You cannot put a superheavy atom under a microscope. Instead, researchers rely on specialized equipment like gas-filled recoil separators, which use electric and magnetic fields to separate the newly created atoms from the overwhelming flood of beam particles and other reaction debris.4Radiation Physics and Chemistry. Towards the “islands of stability” of superheavy elements The recoiling atom is steered into a detector, where it implants itself and then decays.
The decay is the key. Superheavy elements typically decay by emitting alpha particles (clusters of two protons and two neutrons) or by spontaneously splitting apart in fission. Each decay step produces a characteristic energy signature. If you observe a chain of alpha decays that steps down through a sequence of known daughter nuclei, you can work backward and identify the parent. For some of the heaviest nuclei studied theoretically, alpha decay is the dominant mode and the most useful for identification.5Nuclear Physics A. Competition between spontaneous fission ternary fission cluster decay and alpha decay in the super heavy nuclei of Z = 126 Others decay by spontaneous fission, and the predicted half-lives can be extraordinarily short, on the order of nanoseconds for some isotopes of elements 119 and 120.6Modern Physics Letters A. Half-lives and fragments of spontaneous fission of superheavy elements
Because the stakes are so high and the event counts so low, independent confirmation is required before a new element is officially recognized. The joint IUPAC-IUPAP working group reviews claims against formal discovery criteria that have been refined over nearly three decades. The most recent update of those criteria came after the completion of the first seven rows of the periodic table, all 118 elements, and it emphasized how experimental and theoretical advances have changed what counts as sufficient evidence.7Pure and Applied Chemistry. On the discovery of new elements (IUPAC/IUPAP Report)
How New Elements Get Their Names
Once a discovery is verified, the discoverers earn the right to propose a name and a chemical symbol. IUPAC’s rules allow new elements to be named after a mythological concept, a mineral, a place, a country, or a scientist.8International Union of Pure and Applied Chemistry. How to Name New Chemical Elements The proposal goes to IUPAC’s Inorganic Chemistry Division for review and then to a public comment period before being finalized. This process has produced names like oganesson (element 118, after physicist Yuri Oganessian), nihonium (element 113, after Japan), and tennessine (element 117, after the state of Tennessee, where Oak Ridge National Laboratory supplied the berkelium target).
The naming process has not always been smooth. During the Cold War, competing claims between American and Soviet laboratories led to decades of dispute over who deserved credit for discovering several elements in the 100-to-109 range. Elements temporarily carried placeholder names based on their atomic numbers (like “unnilpentium” for element 105) while committees tried to sort out priority. Those disputes eventually drove the creation of the formal discovery criteria now in use.
Synthetic Elements You Encounter Without Realizing It
Most synthetic elements decay so quickly that they have no practical use beyond basic research. But a few are produced in large enough quantities and have long enough half-lives to play important roles in technology and medicine.
Technetium-99m is probably the most consequential synthetic element in daily life. It is the workhorse of diagnostic nuclear medicine, used in imaging of the brain, skeleton, kidneys, liver, and heart. It supports more than 70% of all nuclear imaging procedures worldwide.9ACS Publications (Journal of Medicinal Chemistry). Oldie but Goodie: Is Technetium-99m Still a Treasure Trove of Innovation for Medicine? A Patents Analysis (2000–2022) Hospitals obtain it from compact generators that produce fresh technetium from the decay of molybdenum-99. The isotope emits gamma rays at an energy ideal for imaging, and its six-hour half-life means it delivers a useful signal and then effectively disappears from the body.
Americium-241 sits inside most ionization-type smoke detectors. The small radioactive source emits alpha particles that ionize the air between two electrodes, creating a tiny current. When smoke particles enter the chamber and disrupt that current, the alarm triggers. A typical domestic smoke detector contains about 40 kilobecquerels of americium-241, a quantity low enough that it poses negligible radiation risk under normal use or even in accident scenarios.10Journal of Physics: Conference Series. Evaluation of radiation safety for ionization chamber smoke detectors containing Am-241
Plutonium-238 powers deep-space missions. Its steady heat output from radioactive decay drives radioisotope thermoelectric generators aboard spacecraft like NASA’s Voyager probes and the Perseverance Mars rover. While trace amounts of plutonium exist in nature as a decay product in concentrated uranium deposits, virtually all usable plutonium is manufactured in nuclear reactors.1Research Starter. Man-Made Elements
Why Superheavy Elements Behave Strangely
As you move to heavier and heavier elements, their electrons travel at speeds that approach a meaningful fraction of the speed of light. This changes how the electrons orbit the nucleus in ways that would not be predicted by classical chemistry. In superheavy elements like copernicium (element 112) and element 120, the innermost electron orbitals contract dramatically due to relativistic effects. For example, the size of the 7s orbital in elements around copernicium shrinks to roughly 69% of what non-relativistic calculations predict, while the outer 6d orbitals split into sub-levels separated by several electron-volts of energy.11Nuclear Physics A. Relativistic and quantum electrodynamic effects in superheavy elements
These shifts have real chemical consequences. Flerovium (element 114) sits directly below lead in the periodic table, so you might expect it to behave like a metal. Experiments using gas-phase chromatography on just a few atoms at a time show that flerovium is instead highly volatile and the least reactive member of its column. Its reactivity toward gold surfaces falls somewhere between that of mercury and that of the noble gas radon.12PubMed Central. On the adsorption and reactivity of element 114, flerovium This is precisely what relativistic calculations predicted: the strong contraction and stabilization of flerovium’s outermost electron pair makes the atom reluctant to form bonds. In a sense, the periodic table starts to break down at the superheavy frontier, because elements no longer neatly echo the chemistry of the lighter elements above them.
The Race to Element 119
With all 118 elements in the first seven rows of the periodic table now confirmed, the next frontier is element 119, which would be the first element in a new eighth row. Making it is considerably harder than anything that came before. The calcium-48 strategy that proved so effective for elements 113 through 118 runs into a wall because there is no suitable target nucleus that, combined with calcium-48, yields element 119. Researchers have to switch to heavier projectile beams like titanium-50, which are less efficient at producing surviving fused nuclei.
An attempt was made in 2011 at GSI in Germany using a titanium-50 beam on a berkelium-249 target. The experiment ran for four months but produced no detectable atoms of element 119.13The Bombay Technologist. Superheavy Elements – Elements 119 and 120 The measured production rate was extremely low, confirming that titanium is a far less cooperative projectile than calcium but still one of the more promising options. To improve the odds, RIKEN in Japan has built a new superconducting linear accelerator and ion source designed to deliver beams of significantly higher energy and intensity, specifically aimed at synthesizing element 119 through a hot fusion reaction.14PubMed Central. Facility upgrade for superheavy-element research at RIKEN
Multiple laboratories are now in the running. In addition to RIKEN, groups at the Joint Institute for Nuclear Research in Dubna, Russia, and at other facilities in Germany and China are preparing their own attempts. Even with upgraded accelerators, researchers expect to need months or years of continuous beam time to detect even a single atom. And once an atom is made, its predicted half-life may be on the order of nanoseconds, making detection a formidable challenge on top of the production challenge.6Modern Physics Letters A. Half-lives and fragments of spontaneous fission of superheavy elements
The Island of Stability
A recurring idea in nuclear physics is the “island of stability,” a predicted region of the periodic table where certain combinations of protons and neutrons create nuclei that are unusually long-lived compared to their neighbors. Most superheavy elements decay in fractions of a second, but theoretical models suggest that near certain “magic numbers” of protons and neutrons, the nuclear shell structure becomes especially robust, potentially stretching half-lives to minutes, hours, or even longer.
Where exactly this island sits remains debated. Some models place the center of enhanced stability near 114 protons and 184 neutrons; others favor higher proton counts around 120 or 126. The superheavy elements synthesized so far have generally not had enough neutrons to reach the predicted sweet spot, because the fusion reactions used tend to produce nuclei on the neutron-poor side. Getting closer to the island would require either new reaction strategies or new target-projectile combinations that have not yet been experimentally feasible.
Evidence from the existing superheavy elements offers hints. The fact that flerovium (114 protons) and oganesson (118 protons) have been produced and detected at all, surviving long enough to register in detectors, suggests that some stabilizing shell effects are at work. But the definitive demonstration of a long-lived superheavy nucleus, one you could accumulate and study at leisure, has not been achieved.
Synthetic on Earth, Natural in the Cosmos
The label “synthetic” applies specifically to conditions on Earth. In the broader universe, the nuclear reactions that build heavy elements happen naturally, just in extreme environments that our planet cannot replicate. Neutron star mergers are one of the most important sites. When two neutron stars spiral into each other and collide, the extraordinary densities and neutron fluxes drive what is known as the rapid neutron capture process, or r-process. Simulations of these events produce a broad range of heavy elements, from about mass number 70 up to around 220, with abundance peaks that match what astronomers observe in the composition of the sun and old stars.15Monthly Notices of the Royal Astronomical Society. Neutron star mergers as the dominant contributor to the production of heavy r-process elements
The r-process produces elements like gold, platinum, and uranium, along with many of the radioactive elements that we classify as synthetic. Technetium, for instance, has been detected in the spectra of certain giant stars undergoing a process called third dredge-up, where material from the star’s interior gets mixed to the surface.16Astronomy & Astrophysics. Observational evidence of third dredge-up occurrence in S-type stars with initial masses around 1 M⊙ Since all technetium isotopes are radioactive with geologically short half-lives, its presence in a star’s atmosphere is proof that it was freshly made by nuclear reactions inside the star, not left over from the star’s formation.
This cosmic context reframes what “synthetic” really means. It is not that these elements are fundamentally impossible in nature. It is that they are too unstable to persist on Earth over geological time. The universe has been making them for billions of years in supernovae and neutron star collisions; we just have to rebuild the process, atom by atom, in our laboratories. For the superheavy elements beyond about element 100, even the cosmos may not produce them in detectable amounts, because the nuclear reactions involved require conditions that go beyond what even a neutron star merger routinely delivers. At the heaviest frontier, human ingenuity with particle accelerators and rare actinide targets is, as far as we know, the only pathway to creation.