Argon
An inert noble gas used as a protective atmosphere.
Inside the Argon atom
Switch between Bohr and Quantum Cloud modes to compare a simple teaching model with a more realistic probability-based view, and follow the guided tour to explore the Argon atom step by step.
Electron configuration
[Ne] 3s2 3p6
A neutral Argon atom has 18 electrons (equal to its proton count). Choosing a different isotope above changes only the neutron count.
Shell distribution
Electrons fill inner shells before outer ones; the outermost (valence) shell drives the element's chemistry.
Physical & atomic properties
- State (room temp)
- Gas
- Melting point
- 84 K (-189 °C)
- Boiling point
- 87 K (-186 °C)
- Density
- 0.0017837 g/cm³
- Electronegativity
- —
- Atomic radius
- 71 pm
- 1st ionization energy
- 1521 kJ/mol
- Category
- Noble gases
Discovery & naming
- Discovered
- 1894
- Discovered by
- Lord Rayleigh and William Ramsay
- Origin of name
- Greek 'argos', meaning idle or lazy.
Notable uses
Shielding gas for welding, and filling incandescent bulbs.
Where Argon comes from
Stellar fusion and dying stars
Forged in oxygen and silicon burning, and in the explosive burning of supernovae.
Simplified origin map — many elements form through more than one astrophysical pathway.
Summary
- Atomic number
- 18
- Atomic mass
- 39.948
- Category
- Noble gases
- Group · Period
- 18 · 3
- Block
- p-block
- Shells
- 2 · 8 · 8