18 Ar 39.948
Argon
Noble Gas
Argon (Ar) is a chemical element with atomic number 18, classified as a noble gas. At room temperature it is a gas. It was discovered in 1894 by Lord Rayleigh, William Ramsay.
Properties
- Atomic number
- 18
- Atomic mass
- 39.948 u
- Category
- Noble Gas
- Group
- 18
- Period
- 3
- Block
- p-block
- Electron configuration
- [Ne] 3s² 3p⁶
- Phase at STP
- Gas
- Density
- 1.784 g/L
- Melting point
- 83.8 K (-189.3 °C)
- Boiling point
- 87.3 K (-185.8 °C)
- Electronegativity
- —
- Atomic radius
- 71 pm
- Ionization energy
- 15.76 eV
- Discovery
- 1894 · Lord Rayleigh, William Ramsay
Common uses
Light bulbs, welding, wine preservation, medical lasers
Did you know?
Third most abundant gas in Earth's atmosphere but completely unreactive.