At the furthest reaches of the periodic table, scientists are creating atoms that defy nature's rules, pushing the boundaries of matter itself.
Imagine an element so unstable that it vanishes in less than a millisecond, yet theorists believe versions of it could exist for years. This paradox lies at the heart of superheavy element research, a field where scientists create atoms unknown to nature in a relentless pursuit to answer a fundamental question: where does the periodic table end? For over seventy years, this quest has driven physicists and chemists to extend the frontiers of matter, synthesizing 26 transuranic elements in their determination to map chemistry's final frontier 4 .
The periodic table might have ended with uranium (element 92), the heaviest naturally occurring element, were it not for the nuclear shell model. This model, for which Maria Goeppert Mayer and Johannes Hans Daniel Jensen won the Nobel Prize, proposes that protons and neutrons arrange themselves in discrete energy levels or "shells" within the nucleus 1 . Just as noble gases are chemically inert when their electron shells are full, atomic nuclei gain exceptional stability when their proton or neutron shells are complete.
These special numbers of particles are called "magic numbers." Nuclei with magic numbers of protons or neutrons are significantly more stable than their neighbors. When a nucleus has magic numbers of both protons and neutrons, it is considered "doubly magic" and exhibits remarkable stability—like the well-known isotope lead-208 (Z=82, N=126) 1 .
Special numbers of protons or neutrons that form complete nuclear shells, conferring exceptional stability to atomic nuclei.
A theoretical region of superheavy elements with enhanced stability due to closed nuclear shells.
In the late 1960s, theorists including William Myers, Władysław Świątecki, and Heiner Meldner made a crucial prediction. They calculated that in the superheavy realm, new magic numbers would emerge, possibly at proton number Z=114 or 126 and neutron number N=184 1 3 . When a nucleus has these "closed shells," it would form what they termed an "island of stability"—a region of relatively long-lived isotopes surrounded by a sea of instability where other superheavy nuclei decay in mere instants 1 .
The most promising candidate for this island appears to be the doubly magic isotope flerovium-298 (with 114 protons and 184 neutrons), though its synthesis remains beyond current experimental capabilities 1 . The enhanced stability is expected to result from higher energy barriers against spontaneous fission and alpha decay, potentially extending half-lives from microseconds to minutes, days, or possibly even years 1 .
| Nucleon Type | Known Magic Numbers | Predicted Superheavy Magic Numbers |
|---|---|---|
| Protons (Z) | 2, 8, 20, 28, 50, 82 | 114, 120, 126 |
| Neutrons (N) | 2, 8, 20, 28, 50, 82, 126 | 184 |
| Key Doubly Magic Nuclei | ⁴He (Z=2, N=2), ²⁰⁸Pb (Z=82, N=126) | ²⁹⁸Fl (Z=114, N=184) - Predicted to be at the center of the island of stability |
Theoretical representation showing the "island of stability" where superheavy elements with specific proton and neutron numbers exhibit enhanced stability compared to their neighbors.
Creating superheavy elements is one of modern science's most daunting challenges. Since these elements don't occur naturally, scientists must synthesize them in particle accelerators through fusion reactions 3 . The process is extraordinarily difficult and inefficient—for element 112 (copernicium), researchers might produce just one atom per week despite bombarding targets with trillions of beam particles every second 3 .
Atom produced per week for element 112
One of the colliding nuclei is ionized and accelerated to approximately 10% the speed of light using a particle accelerator 3 6 .
The other nucleus is prepared as a thin, rotating foil target. Elements are chosen so their proton numbers sum to the desired superheavy element 6 .
The accelerated beam is directed onto the target. Occasionally a collision occurs where nuclei fuse into a compound nucleus 3 .
| Element Name | Atomic Number | Symbol | Most Stable Isotope | Half-Life | Discovery Year |
|---|---|---|---|---|---|
| Rutherfordium | 104 | Rf | ²⁶⁷Rf | 2.5 hours | 1969 |
| Dubnium | 105 | Db | ²⁶⁸Db | 1.2 days | 1968 |
| Seaborgium | 106 | Sg | ²⁶⁹Sg | 5 minutes | 1974 |
| Bohrium | 107 | Bh | ²⁷⁰Bh | 3.8 minutes | 1981 |
| Hassium | 108 | Hs | ²⁶⁹Hs | 16 seconds | 1984 |
| Meitnerium | 109 | Mt | ²⁷⁸Mt | 6 seconds | 1982 |
| Darmstadtium | 110 | Ds | ²⁸¹Ds | 14 seconds | 1994 |
| Roentgenium | 111 | Rg | ²⁸²Rg | 2.2 minutes | 1994 |
| Copernicium | 112 | Cn | ²⁸⁵Cn | 30 seconds | 1996 |
| Nihonium | 113 | Nh | ²⁸⁶Nh | 12 seconds | 2004 |
| Flerovium | 114 | Fl | ²⁸⁹Fl | 2.1 seconds | 1999 |
| Moscovium | 115 | Mc | ²⁹⁰Mc | 0.84 seconds | 2003 |
| Livermorium | 116 | Lv | ²⁹³Lv | 70 milliseconds | 2000 |
| Tennessine | 117 | Ts | ²⁹⁴Ts | 70 milliseconds | 2010 |
| Oganesson | 118 | Og | ²⁹⁴Og | 0.7 milliseconds | 2002 |
The half-lives of superheavy elements generally decrease with increasing atomic number, with occasional peaks that hint at increased stability near closed nuclear shells.
Strips electrons from atoms to create positively charged ions for acceleration.
Creates intense beams of calcium or argon ions by combining microwaves and strong magnetic fields 6Prevents beam damage by distributing impact across a larger area; provides target nuclei.
Thin metal foils of plutonium or californium rotate constantly to avoid melting under beam bombardment 6Uses helium gas and electric fields to separate and slow reaction products from unreacted beam particles.
Guides newly created superheavy atoms into detectors for measurement 6Identifies elements by measuring energy and timing of alpha decay (emission of 2 protons + 2 neutrons).
"The Shack" at LBNL records decay patterns that reveal the original atom's composition 6The study of superheavy elements has revealed phenomena that challenge our understanding of chemistry and physics. Due to the immense positive charge in their nuclei, electrons in these atoms are pulled inward at velocities approaching the speed of light. This creates strong relativistic effects that fundamentally alter chemical behavior 6 . For instance, the electron shells become distorted, potentially making some superheavy elements behave unlike their lighter counterparts in the same periodic group.
Perhaps even more intriguing are theoretical suggestions that beyond a certain nuclear charge, the atomic structure itself may become unstable. For these extreme atoms, electron energy levels could merge with a quantum mechanical "negative-energy continuum," potentially leading to real electron-positron pair creation and fundamentally new states of matter 2 .
In superheavy elements, electrons move at speeds approaching light, causing distortions in electron orbitals and unusual chemical properties.
The future of superheavy element research focuses on reaching the center of the island of stability, believed to be around flerovium-298 (Z=114, N=184) 1 . This requires packing more neutrons into nuclei, a challenge current methods struggle with. Future facilities may employ multinucleon transfer reactions or use radioactive beams to access these neutron-rich isotopes 2 . Laboratories worldwide, including RIKEN in Japan and the Joint Institute for Nuclear Research (JINR) in Russia, are actively hunting for elements 119 and 120, which would begin the eighth period of the periodic table 2 6 .
Would be the first element of period 8 and group 1, potentially exhibiting unusual properties due to relativistic effects.
Would be the second element of period 8 and group 2, potentially the next doubly magic nucleus after flerovium-298.
"What are the limits of this concept? What are the limits of atomic physics? Where is the end of chemistry?" — Witold Nazarewicz, theoretical nuclear physicist 6
The quest for superheavy elements represents humanity's relentless drive to explore the fundamental building blocks of our universe. While the practical applications of these fleeting elements remain speculative, their study pushes forward detector technology, accelerator design, and theoretical models. More fundamentally, each new atom synthesized provides crucial data about nuclear structure and the forces that bind matter together. The journey to the island of stability continues to reveal strange new territories at the boundaries of existence, reminding us that the periodic table—once thought to be nearly complete—still holds mysteries waiting to be uncovered.