The element with the greatest atomic number among the noble gases is Oganesson (Og). This superheavy element is the final member of Group 18 on the modern periodic table, the column dedicated to the noble gases. An element’s atomic number is defined by the number of protons contained within the nucleus of its atoms. Oganesson possesses 118 protons, making it the highest-numbered element officially recognized by the International Union of Pure and Applied Chemistry (IUPAC). Its placement in Period 7 signifies it is the heaviest known element, completing the seventh row of the periodic chart.
Oganesson: The Noble Gas with the Highest Atomic Number
Oganesson is the heaviest element that has ever been synthesized and detected by scientists. Its designation as a noble gas is based on its position directly below radon in Group 18. This location suggests it should theoretically share the chemical characteristics of its lighter counterparts.
The element was named in honor of Russian nuclear physicist Yuri Oganessian for his pioneering work in the discovery of superheavy elements. The naming convention follows the pattern for noble gases, which typically end with the suffix “-on,” such as neon, argon, and krypton. Oganesson-294, its only known isotope, holds the highest atomic mass of any element discovered so far.
Defining the Noble Gas Group
The noble gases constitute Group 18 of the periodic table, including helium, neon, argon, krypton, xenon, and radon, in addition to oganesson. These elements are traditionally characterized by their complete valence electron shells. Having eight valence electrons, or two for helium, provides a highly stable configuration known as a full octet, which makes them chemically unreactive under standard conditions. This lack of reactivity is why they were historically referred to as the inert gases.
Under normal conditions, all the naturally occurring noble gases exist as colorless, odorless, monatomic gases. Their atoms are held together only by very weak London dispersion forces, resulting in extremely low melting and boiling points. Because of their stability, they are often utilized in applications where chemical interaction is undesirable. For instance, argon is frequently used as an inert shielding gas in welding, and neon is well-known for its use in electric discharge lighting.
Creation and Instability of Element 118
Unlike the other noble gases, Oganesson is a synthetic element and does not occur naturally on Earth. It is created by fusing two lighter atomic nuclei in a high-energy particle accelerator, a process only achievable in specialized research laboratories. The discovery was achieved by bombarding a target of Californium-249 with a beam of Calcium-48 ions. This complex process yielded only a few atoms of Oganesson-294.
The element exhibits extreme instability due to its large nucleus, making it highly radioactive. Its most stable isotope, Oganesson-294, has an incredibly short half-life of less than one millisecond. This rapid decay severely limits any experimental study of its physical or chemical properties. Theoretical predictions suggest that relativistic effects, which become significant for very heavy elements, dramatically alter its behavior. This could make Oganesson less “noble” than its lighter relatives, causing it to be a solid at room temperature and potentially more reactive, exhibiting properties more like a metalloid.