The world of chemistry is built upon the Periodic Table, a systematic arrangement of the fundamental building blocks of matter we call elements. An element is defined by the number of protons in its nucleus, a value known as the Atomic Number (\(Z\)). Scientists have sought to understand the full extent of this roster, from naturally occurring substances to heavier, man-made creations. The question of whether this table has a finite end continues to drive the frontier of modern physics and chemistry.
The Current Roster of Known Elements
The periodic system currently recognizes 118 distinct elements, with the heaviest being Oganesson (\(Z=118\)), which completes the seventh row of the table. Elements beyond uranium (\(Z=92\)) are classified as transuranium elements, and most are synthetic, meaning they are not found in nature. The discovery and formal naming of any new element is governed by the International Union of Pure and Applied Chemistry (IUPAC). This body confirms the evidence and grants the discoverers the right to propose a permanent name and symbol.
Creating Superheavy Elements in the Laboratory
Creating the heaviest elements requires immense energy to force two atomic nuclei to fuse together, relying on specialized facilities like linear accelerators or cyclotrons. The current method involves nuclear fusion via collision, where scientists fire a beam of lighter nuclei, such as calcium-48, at a heavy target nucleus. The goal is to overcome the strong electromagnetic repulsion between the positively charged protons in both nuclei, known as the Coulomb barrier. If the nuclei collide with sufficient energy, they may briefly merge to form a single, highly unstable compound nucleus. Because this superheavy atom exists for only a fleeting moment before decaying, detection relies on tracing the distinct chain of decay products.
Physical Constraints That Limit Discovery
The search for new elements is fundamentally limited by the powerful physical forces at play within the atomic nucleus. As the Atomic Number (\(Z\)) increases, the repulsive force between the growing number of protons increases exponentially, requiring ever-greater energy to initiate a fusion reaction. This enormous repulsive energy is the Coulomb barrier, which must be overcome for the two nuclei to merge. Scientists often must inject “extra-push energy” to achieve temporary fusion, but the resulting nucleus remains extremely prone to immediate fission.
The stability of the electron cloud surrounding the nucleus also becomes compromised by the sheer number of protons. For elements with high atomic numbers, the innermost electrons are accelerated to speeds approaching that of light, making relativistic effects significant. This extreme speed causes the inner s-orbitals to contract and bind more tightly to the nucleus, while the outer d- and f-orbitals expand. This warping of the electron structure disrupts the predictable periodic trends, fundamentally altering the element’s chemical properties. Calculations suggest that beyond an atomic number of approximately \(Z=137\), the standard models of electron behavior break down entirely.
The Search for the Island of Stability
The current frontier of discovery is focused on the theoretical Island of Stability, a concept that counteracts the trend of increasing instability. This theory is based on the nuclear shell model, suggesting that nuclei with specific, “magic” numbers of protons and neutrons create a closed, highly stable shell structure. The main predicted location centers around Flerovium (\(Z=114\)) with the sought-after neutron magic number \(N=184\). If atoms in this region can be synthesized, their half-lives are predicted to be significantly longer than the milliseconds seen in current superheavy elements, potentially lasting minutes, days, or even millions of years.