Radon (Rn) is a colorless, odorless, and chemically inert noble gas. It is a naturally occurring radioactive gas, produced continuously from the decay of uranium and thorium found in rock and soil. The history of its name is complex, reflecting the rapid pace of radioactive discovery at the turn of the 20th century. This narrative traces the path from the first observations of a mysterious radioactive “emanation” to the final, internationally accepted name of Radon.
The Initial Discovery of Radioactive Gas
The first scientific observation of the phenomenon that would eventually be identified as Radon occurred in 1899 at McGill University in Canada. Physicist Ernest Rutherford noticed that compounds containing thorium continuously emitted a substance that made the surrounding air radioactive. He named this invisible, short-lived phenomenon the “thorium emanation” (Th Em). This observation suggested a radioactive material was behaving like a gas.
The following year, in 1900, German physicist Friedrich Ernst Dorn made a similar, independent discovery while working with radium. Dorn observed that radium compounds released a radioactive gas that he referred to as “radium emanation” (Ra Em). This specific emanation, later identified as the isotope Radon-222, proved to have a longer half-life than Rutherford’s thorium variety. Both scientists were observing the physical effect of a gaseous product of radioactive decay, but they had not yet confirmed it as a distinct chemical element.
The Period of Conflicting Names
The simultaneous discovery of “emanations” from radium, thorium, and actinium created a confusing state of affairs in early atomic science. It was uncertain whether the gaseous products from each source were isotopes of the same element or entirely separate substances. The general term “emanation” was used broadly, while specific emanations were often labeled based on their parent element, such as “Radium Emanation” or “Thorium Emanation.”
To establish a proper chemical identity, Sir William Ramsay and Robert Whytlaw-Gray isolated the gas in 1909 and determined its density, confirming it as the heaviest gas known. Recognizing the awkwardness of the “radium emanation” designation, they proposed the new name “Niton” (Nt) in 1910. This name was derived from the Latin word nitens, meaning “shining,” referencing the brilliant phosphorescence the gas exhibits when cooled below its freezing point.
The name Niton gained traction and was accepted by the International Commission for Atomic Weights in 1912. However, other researchers continued to use names associated with the parent element. This instability in chemical nomenclature highlighted the need for a unified system to classify the newly discovered radioactive decay products.
Standardization and the Etymology of “Radon”
The problem of multiple names for what was confirmed to be a single element with various isotopes (Rn-222, Rn-220, Rn-219) was finally resolved by international scientific bodies. In 1923, the International Committee for Chemical Elements and the International Union of Pure and Applied Chemistry (IUPAC) made a definitive ruling. They officially adopted the name “Radon” for the element, along with the chemical symbol Rn.
The choice of “Radon” was a systematic decision that honored the element’s origins and chemical properties. The prefix “Rad-” was taken directly from Radium, the element whose most stable decay product had been intensively studied. The suffix “-on” was chosen to conform with the naming convention established for other noble gases, such as Argon, Neon, Krypton, and Xenon. This two-part etymology linked the element to its parent source and classified it within its chemical family, providing the clarity needed for its permanent inclusion in the periodic table.