18Ar39.95
Argon
Noble gasesColourless gases with full outer shells, so they hardly ever react.
[Ne] 3s² 3p⁶
- Atomic number
- 18
- Atomic mass
- 39.95
- Protons
- 18
- Neutrons
- 22 (most common)
- Electrons
- 18
- Shells
- 2, 8, 8
- State at 25 °C
- Gas
- Position
- Group 18, period 3
Proton (+)Neutron (0)Electron (−)
Discovered byLord Rayleigh and William Ramsay, 1894William Ramsay: 5 elementsLord Rayleigh: 1 element
Rayleigh noticed nitrogen from air was slightly heavier than nitrogen made in the lab. The difference was a hidden gas: argon.
Did you know?
- Its name means “lazy” in Greek, because it hardly reacts.
- It is the most common noble gas in air.
Where it's found
- About 0.9% of the air
What it's used for
- Filling light bulbs
- Shielding gas for welding
- Double-glazed windows
Try it
There's no safe home experiment for Argon. Explore it with the animated atom above instead.