Newest Elements on the Periodic Table: Completing the Seventh Period

The Four Newest Named Elements

Nihonium (Nh, Element 113): First synthesized by a team at RIKEN in Wako, Japan, in 2004 by bombarding bismuth-209 with zinc-70 ions. The discovery was confirmed after the team observed a complete alpha decay chain from element 113 down to known elements. Nihonium is named after "Nihon," the Japanese word for Japan, making it the first element discovered and named in an Asian country. Its most stable known isotope, nihonium-286, has a half-life of roughly 20 seconds. Nihonium is predicted to be a poor metal in group 13, below thallium, though relativistic effects on its electrons may give it unexpected properties.

Moscovium (Mc, Element 115): First synthesized in 2003 through a collaboration between the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, and Lawrence Livermore National Laboratory in the United States. The team fired calcium-48 ions at americium-243 targets. Moscovium is named after Moscow Oblast, the Russian region where JINR is located. Its longest-lived known isotope, moscovium-290, has a half-life of about 0.65 seconds. Moscovium is expected to be in group 15, below bismuth, and would likely behave as a heavy metal if enough could be produced to study.

Tennessine (Ts, Element 117): Produced in 2010 through the same JINR-Livermore collaboration, using calcium-48 projectiles on a berkelium-249 target. Obtaining enough berkelium for the experiment was itself a major challenge, requiring months of irradiation at Oak Ridge National Laboratory in Tennessee, which is reflected in the element's name. Tennessine-294, the longest-lived isotope, has a half-life of about 51 milliseconds. As a member of group 17 (the halogens), tennessine is predicted to have some halogen-like properties, though relativistic effects may make it behave more like a metalloid than a true halogen.

Oganesson (Og, Element 118): The heaviest element officially recognized, first produced in 2002 at JINR by bombarding californium-249 with calcium-48. Named after Yuri Oganessian, the Russian nuclear physicist who led the superheavy element research program, oganesson is one of only two elements named after a living person at the time of naming (the other being seaborgium). Oganesson-294 has a half-life of about 0.7 milliseconds. Though it sits in group 18 with the noble gases, theoretical calculations predict that oganesson's electron shell structure is so distorted by relativistic effects that it may be a reactive solid rather than an inert gas, a dramatic departure from the behavior of lighter noble gases.

How Superheavy Elements Are Created

Superheavy elements cannot be found in nature because they decay far too quickly to have survived from the formation of the solar system. They must be created artificially in particle accelerators. The general approach involves accelerating a beam of lighter ions to roughly 10 percent of the speed of light and directing them at a target made of a heavy element. When a projectile nucleus and a target nucleus fuse, they briefly form a compound nucleus that may survive as a new superheavy atom or, far more commonly, immediately break apart.

The probability of successful fusion is extraordinarily small. For oganesson, scientists estimated that only about one atom was produced for every 10^19 (ten billion billion) calcium ions fired at the target. Experiments often run continuously for months, producing only a handful of atoms in total. Detection relies on observing the characteristic alpha decay chains: when a superheavy atom decays, it emits a series of alpha particles, and the energies and timing of these emissions create a fingerprint that identifies the parent element.

Calcium-48 has been the projectile of choice for superheavy element synthesis since the late 1990s because it is doubly magic (having 20 protons and 28 neutrons, both magic numbers that confer extra nuclear stability), making fusion reactions more likely to produce surviving nuclei. The supply of suitable heavy-element targets is a practical limitation: berkelium and californium must themselves be produced in nuclear reactors through lengthy irradiation campaigns.

The Island of Stability

Nuclear theory predicts that certain combinations of protons and neutrons, near so-called magic numbers, produce nuclei with enhanced stability. The concept of an "island of stability" suggests that superheavy elements around atomic numbers 114 to 126, with approximately 184 neutrons, might have significantly longer half-lives than their neighbors, potentially ranging from minutes to years or even longer. This would make it possible to produce enough material to study their chemistry directly.

Current experimental evidence provides tentative support for this prediction. Flerovium (element 114) and its neighbors show longer half-lives than elements slightly lighter on the periodic table, suggesting that the island of stability may indeed exist, though the elements produced so far are still far from the predicted center of the island because they have too few neutrons. Reaching the true island would require producing more neutron-rich isotopes, which demands new experimental techniques beyond current capabilities.

Elements Beyond 118

Research groups at JINR, RIKEN, and other laboratories are actively attempting to synthesize elements 119 and 120, which would begin the eighth period of the periodic table. Element 119 would be an alkali metal below francium in group 1, and element 120 would be an alkaline earth metal below radium in group 2. However, the cross-sections (probabilities) for producing these elements are expected to be even smaller than for oganesson, and experiments may need to run for years to observe a single atom.

Theoretical physicists have extended periodic table predictions to element 172 and beyond, though whether such elements can actually exist as discrete atoms with identifiable chemical properties remains an open question. At very high atomic numbers, the strong nuclear force may be insufficient to hold the nucleus together even briefly, and electron behavior becomes so dominated by relativistic effects that the periodic table's group-based property predictions may break down entirely.

Naming New Elements

The process for naming a new element involves several stages. First, a team claims discovery by publishing evidence in peer-reviewed journals. The International Union of Pure and Applied Chemistry (IUPAC) and the International Union of Pure and Applied Physics (IUPAP) convene a Joint Working Party to evaluate priority claims, which can take years. Once priority is established, the discoverers propose a name following IUPAC guidelines: elements can be named after a mythological concept, a mineral, a place, a property of the element, or a scientist. The name must end in "-ium" for most elements, "-ine" for group 17 halogens, or "-on" for group 18 noble gases. A five-month public review period follows before the name becomes official.

Before receiving permanent names, newly discovered elements carry systematic placeholder names based on their atomic number using Latin and Greek roots. Element 118 was temporarily called "ununoctium" (un-un-octium = 1-1-8) before becoming oganesson. As the element discovery guide details, the history of naming elements has often been contentious, with competing claims and national pride influencing the process.