Argon is an unreactive atmospheric gas used wherever unwanted reactions need to be limited. It shields hot metal during welding and fills some insulating windows. Some terrestrial argon forms through radioactive decay of potassium-40, connecting a useful gas to changes inside atomic nuclei.
FROM ELEMENT TO APPLICATION
AN ELEMENT IN CONTEXT
How does argon between window panes reduce heat transfer without blocking the view?
Argon gas enclosed between panes
FOLLOW THIS RELATIONSHIP
Separate the glazing layers
Multiple panes create an enclosed space that becomes part of the window's thermal system while allowing visible light through the glazing assembly.
Explore the model (optional)
ArFORM → INTERACTION → CONSEQUENCE
Follow the explanation in either direction. These are authored steps, not a physical clock.
Optional: check your understanding
USE THE EXPLANATION
What isolates the gas-fill effect?
Atomic identity, reference properties and structure models
INTERACTIVE 3D18 visible sites
An electron censusDrag to rotate · scroll or pinch to zoom
[Ne] 3s2 3p6. Grouping electrons by principal shell connects the neutral-atom configuration to periodic-table patterns.
What this representation means
A three-dimensional counting diagram. Dots are count markers, not measured electron positions; spherical placement and spacing are arbitrary. There are no electron trajectories here. Orbitals describe quantum states.
Cavendish noticed an unreactive residue in air in 1785, but its identity remained unresolved. Later, Rayleigh found that nitrogen obtained from air differed in density from nitrogen prepared chemically. Rayleigh and Ramsay traced the discrepancy to another atmospheric gas and announced argon in 1894. A small measurement difference helped reveal an entire new category of elements.
1785
Residual gas observed
Cavendish observed a small unreactive part of air.
1894
Argon isolated
Rayleigh and Ramsay identified the gas behind a density discrepancy.
Argon is a constituent of the atmosphere and can be separated during the processing of liquefied air. It is collected as a gas rather than mined as a conventional . Its atmospheric occurrence supplies applications that need a protective environment with little chemical participation from the surrounding gas.
Argon is a colourless noble gas with low chemical reactivity under ordinary conditions. That behavior helps explain its use around hot or reactive materials. Electrical excitation can nevertheless make the gas emit light: chemical reluctance to react does not mean that its atoms cannot exchange energy with their surroundings.
Each section links its supporting references. Descriptions and diagrams were authored for this atlas. Source checks completed. Source checks dated 2026-09-06.
CITE THIS PAGE
Family labels and the group-3 layout are teaching conventions. A table position does not establish an unknown bulk property. Electronic configurations refer to neutral atoms; ions and material environments require their own account.
Read each reference property together with its units, conditions and the reference information below.
Not yet recorded: electron affinity, second ionization energy, ground-state term symbol, van der waals radius, thermal conductivity, specific heat capacity, electrical resistivity, crystal structure, lattice parameter a, space group, abundance in seawater, abundance in the universe, annual production, supply-risk listing, hazard classification, biological role, cas registry number, pubchem cid, wikidata item. These families are declared and awaiting an ingestion run against the source each names; they are listed here rather than shown as empty rows.
Physical
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Phase at 20 °C
gas
293.15 K, 101.325 kPa
Melting point in K
83.8 K
at standard pressure unless noted
Boiling point in K
87.3 K
101.325 kPa
Density in g/cm³
0.00178 g/cm³
solids and liquids at 293 K; gases at 273 K and 101.325 kPa
Atomic and electronic
Intended reference: Pauling electronegativity scale · Widely tabulated; original in The Nature of the Chemical Bond
Electronegativity
Not applicable
Pauling scale
First ionization energy in kJ/mol
1521 kJ/mol
gas-phase neutral atom, ground state
Covalent radius in pm
106 pm
single-bond covalent radius
Common oxidation states
0
states met in ordinary compounds; not exhaustive
Occurrence and identity
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Abundance in the crust in mg/kg
3.5 mg/kg
upper continental crust, mass fraction
Has stable isotopes
Yesderived
Discovery year in CE
1894 CEderived
WHERE IT SITS AMONG ITS NEIGHBORS
Electronegativity across period 3
Na 0.93 Pauling · Sodium
Electronegativity across period 3. Exact values.
Na
0.93
Mg
1.31
Al
1.61
Si
1.9
P
2.19
S
2.58
Cl
3.16
Electronegativity down group 18
Kr 3 Pauling · Krypton
Electronegativity down group 18. Exact values.
Kr
3
Xe
2.6
The trend uses the same reference-property values as the periodic table. Elements with no recorded value are left out of the line rather than drawn at zero.
