18 Ar 39.948
Argon
noble gas
Properties
- Atomic number
- 18
- Atomic mass
- 39.948 u
- Category
- noble gas
- Group
- 18
- Period
- 3
- Block
- p-block
- State (room temp)
- Gas
- Outer-shell electrons
- 8
- Electronegativity
- —
- Density
- —
- Melting point
- -189.34 °C
- Boiling point
- -185.85 °C
Electron configuration
1s² 2s² 2p⁶ 3s² 3p⁶
Noble-gas shorthand: [Ne] 3s² 3p⁶
Electrons per shell: 2, 8, 8 — that's 8 in the outermost shell.
About Argon
Argon is a chemical element with symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third most common gas in the Earth's atmosphere, at 0.934% (9,340 ppmv), making it over twice as abundant as the next most common atmospheric gas, water vapor (which averages about 4000 ppmv, but varies greatly), and 23 times as abundant as the next most common non-condensing atmospheric gas, carbon dioxide (400 ppmv), and more than 500 times as abundant as the next most common noble gas, neon (18 ppmv).
- Discovered by Lord Rayleigh
- Appearance: colorless gas exhibiting a lilac/violet glow when placed in a high voltage electric field
Position in the periodic table
Data compiled from Wikipedia, PubChem, and IUPAC. Source.