ارجن is a chemical element with the symbol Ar and atomic number 18. It is a colorless, odorless, and tasteless gas that belongs to the noble gases group in the periodic table. ارجن is the third most abundant gas in the Earth's atmosphere, making up about 0.93% of it. This element is primarily used in various applications, including lighting and welding. ارجن is often found in fluorescent lamps and is used to create an inert atmosphere for processes like welding to prevent oxidation. Its non-reactive nature makes it valuable in scientific research and industrial applications.