#atomic structure layout
- Argon — A chemical element with atomic number 18 and symbol Ar, representing a noble gas that is colorless, odorless, and tasteless, constituting approximately 0.93% of the Earth's atmosphere. In a structural sense, argon has a fully populated and stable outer electron shell (octet), giving it remarkable chemical inertness; it is widely used in industry as a protective atmosphere for gas tungsten arc welding, electronics manufacturing, and incandescent light bulb filling.