Argon is a chemical element with the symbol Ar and atomic number 18. It belongs to group 18 of the periodic table, known as the noble gases, which are characterized by their chemical inertness

. It is a colorless, odorless, tasteless, and non-toxic gas that makes up about 0.93% of Earth's atmosphere by volume, making it the third most abundant gas after nitrogen and oxygen

. Argon is chemically inactive because it has a full outer electron shell, which makes it very stable and resistant to forming chemical bonds

. Argon is primarily produced industrially by fractional distillation of liquefied air, as it occurs naturally in the atmosphere

. It is widely used as an inert shielding gas in welding and high-temperature industrial processes to prevent unwanted chemical reactions, such as oxidation or combustion

. Argon is also used in incandescent and fluorescent lighting, gas-discharge tubes, and gas lasers

. On Earth, most argon is the isotope argon-40, which is produced by radioactive decay of potassium-40 in the Earth's crust, whereas in the universe argon-36 is the most common isotope, formed by stellar nucleosynthesis

. In summary, argon is a naturally occurring, inert noble gas used extensively in industrial applications for its chemical stability and abundance in the atmosphere