A chemical element represents a fundamental substance where all atoms share the same number of protons. This unique proton count, known as the atomic number, defines each element and its position on the periodic table. For instance, every oxygen atom consistently possesses eight protons, making its atomic number eight. While many elements occur naturally, scientists also extend the known elements by creating new ones in laboratory settings.
Discovering Elements in Nature
Early element discoveries involved chemical isolation techniques. Hennig Brand, a German alchemist, isolated phosphorus in 1669 by heating residues from evaporated urine, marking the first discovery of an element unknown since antiquity. Later, in the 18th century, scientists like Carl Wilhelm Scheele and Joseph Priestley independently isolated oxygen by heating various compounds. Antoine Lavoisier subsequently characterized oxygen’s role in combustion, providing a more complete understanding of this newly identified element.
The development of spectroscopy in the 19th century revolutionized element discovery by allowing identification based on unique light signatures. Robert Bunsen and Gustav Kirchhoff pioneered this technique, discovering cesium in 1860 by observing its distinct blue spectral lines in mineral water samples. Soon after, in 1868, astronomers Pierre Janssen and Norman Lockyer independently observed an unknown yellow line in the sun’s spectrum during a solar eclipse. Lockyer proposed this indicated a new element, which he named helium, after the Greek word for the sun, marking the first element identified extraterrestrially before its terrestrial isolation. These advancements expanded the known elements and deepened understanding of the universe’s composition.
The Search for Synthetic Elements
Modern element discovery extends beyond naturally occurring substances to the creation of synthetic elements. These heavy, often unstable elements are produced in laboratories, pushing the boundaries of the periodic table. A primary motivation for creating these superheavy elements is the exploration of the “island of stability,” a theoretical region where certain combinations of protons and neutrons might result in nuclei with longer lifetimes than their immediate neighbors. This concept suggests that while these elements would still be radioactive, their enhanced stability could allow for more detailed study.
Particle accelerators serve as the primary tools in this endeavor, providing the necessary conditions for nuclear reactions. These machines accelerate beams of lighter atoms to immense speeds. The accelerated “projectile” atoms are then directed towards a “target” atom. This high-speed collision aims to fuse the nuclei of the projectile and target, forming a new, heavier element. The energies involved are substantial, overcoming the natural repulsion between positively charged atomic nuclei.
Scientists design these experiments to carefully select the projectile and target elements, aiming for specific proton and neutron combinations. The process requires highly specialized facilities capable of generating and controlling these high-energy beams. The execution is complex, involving precise control over the collision parameters. The goal is to produce a fused nucleus with an atomic number never before observed.
Creating and Detecting New Elements
The creation of new synthetic elements involves nuclear fusion, where the nuclei of two different atoms combine to form a single, heavier nucleus. This is achieved by accelerating a beam of lighter “projectile” atoms to a fraction of the speed of light and then directing them to collide with a heavier “target” atom. For instance, to create element 118, Oganesson, researchers bombarded californium-249 with calcium-48 ions. This intense collision allows the nuclei to overcome their natural electrostatic repulsion and fuse together, forming a new, superheavy atomic nucleus.
A significant challenge in creating these superheavy elements lies in their extreme instability, often decaying within fractions of a second. The newly formed nucleus exists for an incredibly short period before undergoing a series of radioactive decays. Detecting these fleeting atoms requires highly sophisticated methods capable of identifying their unique decay signatures.
Instead, researchers identify new elements by tracing their decay chains. When a superheavy nucleus decays, it typically emits alpha particles, transforming into a lighter “daughter” nucleus, which then also decays. Detectors precisely measure the energy and timing of these emitted particles and the subsequent decay products. By analyzing this specific sequence of decays, scientists can work backward to confirm the initial formation of the predicted new element and its atomic number.
Confirming and Naming Discoveries
After a research team reports the creation of a potential new element, the discovery undergoes a rigorous confirmation process. Independent research teams in different laboratories must reproduce the results to verify the initial findings. This independent verification ensures the scientific community accepts the discovery. Scientists meticulously review the experimental data and methodologies to confirm the element’s unique properties and decay characteristics.
The International Union of Pure and Applied Chemistry (IUPAC) plays a central role in evaluating the evidence for new element discoveries. This international body, along with the International Union of Pure and Applied Physics (IUPAP), convenes a joint working group to assess the claims. Once IUPAC officially recognizes a discovery, the discoverers are invited to propose a name and a chemical symbol for the new element.
The naming process follows established guidelines, with elements often named after scientists, geographical locations, mythological concepts, or properties of the element. After the proposed name and symbol are submitted, IUPAC reviews them for consistency and appropriateness. This process ensures a standardized and globally accepted nomenclature for all elements, integrating new discoveries seamlessly into the periodic table.