Argon is a chemical element with symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third most common gas in the Earth's atmosphere, at 0.934% (9,340 ppmv), making it over twice as abundant as the next most common atmospheric gas, water vapor (which averages about 4000 ppmv, but varies greatly), and 23 times as abundant as the next most common non-condensing atmospheric gas, carbon dioxide (400 ppmv), and more than 500 times as abundant as the next most common noble gas, neon (18 ppmv).
Three reasons Argon stands out
1
Used in light bulbs and welding.
2
It makes up about 1% of Earth's atmosphere, making it the most abundant noble gas we breathe.
3
Sealed cases filled with this gas are used to preserve ancient documents like the Magna Carta.
An unnoticed blanket around the planet
Argon makes up almost one percent of the atmosphere, more than carbon dioxide, yet it went unrecognized because it reacts so little. Its chemical quietness creates protective atmospheres for welding, metal production, and sensitive experiments. In lamps, electrical excitation gives argon a violet-blue glow.
Recognizing Argon in Elementle
If Argon is the mystery element, guesses below atomic number 18 point up and guesses above it point down. Its symbol is Ar: a green letter matches the same position in that symbol, while a yellow letter belongs in another position.
The family clue turns green for noble gas guesses. Compare Neon (Ne), number 10 and Helium (He), number 2: they share the family clue, but their atomic numbers and symbols help you tell them apart.
Values are reference data, not a specification for every temperature, pressure, or allotrope. Unknown properties are left unavailable. Superheavy-element predictions remain uncertain.
The introduction and original editorial story are adapted from Wikipedia contributors via Periodic-Table-JSON. Element descriptions and their adaptations are available under CC BY-SA 3.0. Numerical attributes use the PubChem periodic-table dataset, retrieved September 22, 2026.