Atomic number: 18

Symbol: Ar

Category: non-metal

Density at 25°C: gas

Argon is another noble gas that is very stable. It is essentially unreactive. But it is is useful in lighting and some furnace, high temperature welding to protect against other chemical reactions.


Argon in an electric discharge tube. image: wikipedia

Argon has been found to form compounds in space as the result of high energy explosions of supernova stars. Argon hydride ions (ArH) have been found in the Crab Nebula.

Use, natural applications or common combinations: 

  • Lighting
  • Welding for protection
  • Lasers, also it is produced in supernovas.
  • Toy plasma balls.

Basic characteristics:

  • Standard atomic weight:39.948(1)
  • Melting point: −189.35 °C
  • Boiling point: −185.85 °C
  • Radioactivity: most are stable
  • 39Ar occurs in trace amounts naturally in the atmosphere with half life of 269 years.