What is argon?
Argon (symbol Ar) is element 18 on the periodic table, a noble gas in period 3, group 18. The third most common gas in the air, and completely uninterested in reacting with any of it. At room temperature it is a gas.
The story
What argon is, and how we found it
Third most abundant gas in atmosphere. Nearly inert (HArF exists below 17 K).
The discovery of argon
The Discovery and History of Argon
The Nitrogen Anomaly
The discovery of argon began with a puzzling discrepancy that would torment scientists for over a century. In 1785, Henry Cavendish (1731-1810), the eccentric British nobleman and scientist, conducted a remarkable experiment in his private laboratory at Clapham Common. Using electric sparks to combine atmospheric nitrogen with oxygen, he noticed that a tiny bubble of gas - roughly 1/120th of the original volume - stubbornly refused to react.
Cavendish reported in the Philosophical Transactions of the Royal Society in 1785 that a small bubble of gas, no more than 1/120 of the original nitrogen, refused to react. This observation would lie dormant for over a century.
Lord Rayleigh's Persistent Precision
John William Strutt, 3rd Baron Rayleigh (1842-1919), faced a maddening contradiction in his private laboratory at Terling Place, Essex, during the 1890s. While attempting to verify atomic weights with high precision, he found that a glass globe filled with nitrogen extracted from air consistently weighed more than the same globe filled with nitrogen produced from chemical compounds: about 2.310 grams of gas against 2.299 grams.
This difference of about 0.01 gram - roughly 0.5% - would have been dismissed by most scientists as experimental error. But Rayleigh, with his obsessive attention to detail, repeated the measurements dozens of times over three years. He tried different sources: nitrogen from nitric oxide, nitrogen from nitrous oxide, nitrogen from ammonium compounds - all yielded the lighter weight. Only atmospheric nitrogen remained stubbornly heavy.
Frustrated, Rayleigh published a letter in Nature magazine on September 29, 1892: "I am much puzzled by some recent results as to the density of nitrogen, and shall be obliged if any of your chemical readers can offer suggestions as to the cause."
William Ramsay's Chemical Genius
Sir William Ramsay (1852-1916), the brilliant Scottish chemist at University College London, read Rayleigh's letter with intense interest. Ramsay possessed the chemical expertise to complement Rayleigh's physical measurements.
In early 1894, Ramsay began parallel experiments using a different approach. Instead of removing oxygen and water vapor from air, he attempted to remove nitrogen itself, leaving behind whatever might remain. Using red-hot magnesium to absorb nitrogen (3Mg + N₂ → Mg₃N₂), Ramsay gradually consumed all the nitrogen from a sample of air.
After weeks of careful work, a persistent residue remained - approximately 1% of the original volume. This gas refused to react with any chemical reagent Ramsay tried: sodium, potassium, phosphorus, or the most aggressive acids and bases.
The Collaborative Breakthrough
Realizing they were investigating the same phenomenon, Rayleigh and Ramsay began collaborating in April 1894. Their combined expertise - Rayleigh's precision measurements and Ramsay's chemical synthesis - proved decisive.
Working in parallel laboratories connected by frequent letters and telegrams, they isolated pure samples of the mysterious gas. Rayleigh measured its density: 19.9 times heavier than hydrogen, compared to nitrogen's 14.0. Ramsay determined its spectrum: completely unlike any known element, with brilliant red and green lines never before observed.
The gas was completely chemically inert - it formed no compounds whatsoever, defying contemporary theories of chemical bonding. Ramsay attempted to force reactions using every known method: electric discharges, very high temperatures, powerful oxidizing agents, even fluorine gas. Nothing worked.
Naming the "Lazy" Element
On August 13, 1894, at the British Association meeting in Oxford, Rayleigh and Ramsay jointly announced their discovery. They proposed the name "argon" from the Greek "argos" meaning "lazy" or "inactive," referring to its very low reactivity.
The announcement created immediate controversy. Dmitri Mendeleev (1834-1907), creator of the periodic table, initially refused to accept argon's existence, arguing that no element could be very low reactivity. The discovery challenged fundamental assumptions about atomic bonding and required expanding the periodic table to accommodate noble gases.
Validation and Recognition
Skepticism gradually dissolved as other scientists replicated the experiments. Moissan's attempts to force argon reactions with fluorine failed completely, confirming its inertness. William Crookes's spectroscopic analysis revealed argon's unique atomic signature.
The Royal Society awarded Ramsay the Davy Medal in 1895. Rayleigh received the 1904 Nobel Prize in Physics "for his investigations of the densities of the most important gases and for his discovery of argon in connection with these studies," while Ramsay received the 1904 Nobel Prize in Chemistry "in recognition of his services in the discovery of the inert gaseous elements in air, and his determination of their place in the periodic system."
Opening the Noble Gas Family
Argon's discovery transformed chemistry by revealing an entirely new family of elements. Ramsay subsequently discovered helium (1895), neon (1898), krypton (1898), and xenon (1898), establishing the noble gas group.
This work forced a complete revision of the periodic table, adding Group 18 (formerly Group 0) and demonstrating that Mendeleev's system could accommodate entirely unexpected elements. The discovery also validated the power of precision measurement - a 0.6% density difference led to fundamental discoveries about atomic structure.
Industrial Development
Commercial argon production began in the early 20th century with the development of air liquefaction technology. Carl von Linde's (1842-1934) air separation plants, originally designed for oxygen production, were modified to extract argon as a valuable byproduct.
Georges Claude (1870-1960) pioneered industrial applications, using argon in early electric lighting and establishing the foundation for modern industrial gas industries. By 1930, companies like L'Air Liquide and Linde were producing thousands of tons of argon annually for emerging welding and metallurgical applications.