- Argon (Ar) is a colorless, odorless, tasteless noble gas with atomic number 18, positioned in Group 18 of the periodic table.
- It has a complete octet of electrons in its outermost shell, making it chemically inert under most conditions. Its atomic structure consists of eighteen protons, typically twenty-two neutrons, and eighteen electrons arranged in three shells (two in the first shell, eight in the second, and eight in the third).
- Argon has three stable isotopes: argon-36 (³⁶Ar), about 0.3365% of natural argon; argon-38 (³⁸Ar), about 0.0632%; and argon-40 (⁴⁰Ar), the most abundant at about 99.6003%, produced mainly by the radioactive decay of potassium-40 in Earth’s crust.
- Argon is the third most abundant gas in Earth’s atmosphere, comprising about 0.934% by volume, making it the most common noble gas on the planet. It is obtained commercially by the fractional distillation of liquid air, alongside oxygen and nitrogen. Its abundance is due largely to the decay of potassium-40 in rocks, which releases argon-40 into the atmosphere over geological timescales.
- The element was discovered in 1894 by Lord Rayleigh and Sir William Ramsay while they were investigating discrepancies in the density of nitrogen gas. By removing oxygen, nitrogen, and other known gases from air, they isolated a new heavier gas that did not react chemically, which they named “argon” from the Greek argos, meaning “lazy” or “inactive,” in reference to its inertness.
- Because argon is chemically nonreactive, it has important applications where an inert atmosphere is required. In industry, argon is used in arc welding and cutting to protect metals from oxidation and other reactions with air. In electronics manufacturing, it prevents unwanted chemical changes during the production of semiconductors. Argon is also used to fill incandescent and fluorescent light bulbs, preventing filament oxidation and prolonging bulb life. In double-glazed windows, argon gas is used as an insulating layer to improve energy efficiency.
- In scientific research, liquid argon is employed in particle physics detectors, such as neutrino experiments, because of its scintillation and ionization properties. Argon is also used as a carrier gas in gas chromatography and as a protective blanket in the storage of highly reactive materials.
- Chemically, argon is one of the most inert elements, and under normal conditions it does not form stable compounds. Only under extreme conditions—such as in low-temperature matrices or with highly reactive species like fluorine—can argon form short-lived compounds, such as argon fluorohydride (HArF), which is stable only at cryogenic temperatures.
- Biologically, argon has no known essential role in life processes and is non-toxic. In high concentrations, however, it can act as an asphyxiant by displacing oxygen in enclosed spaces. Because of its inertness and prevalence, argon is considered one of the safest industrial gases to handle when proper ventilation is maintained.
