Argon
noble gas · period 3 · group 18 (noble gases) · p-block
Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas.
What the numbers say
At standard temperature and pressure Argon is a gas, sitting in period 3, group 18 of the p-block.
Its melting point of 84 K (-189 °C) is the 104th highest of the 110 elements with a measured value — among the lowest-melting elements.
At 0.002 g/cm³ it is the 90th densest of 96 elements with a quoted density.
In the solid state it takes a face-centered cubic structure — FCC packing gives 12 independent slip systems, which is why FCC metals are the ductile, formable ones.
First identified in 1894.
Crystal structure
Solid Argon adopts a Face-centered Cubic arrangement, in the Cubic (isometric) system — axes a = b = c, angles α = β = γ = 90°. Symmetry controls the anisotropy of stiffness and thermal expansion, and the available slip systems set how far the metal deforms before it fractures.
Check it against computed structures
The structure search queries the Materials Project, OQMD and the Open Materials Database for computed crystal structures containing Ar — with DFT formation energy, hull stability and band gap where the provider publishes them.
K 2 · L 8 · M 8
Properties
| Atomic number | 18 |
|---|---|
| Atomic mass | 39.9481 u |
| Series | noble gas |
| Group | 18 |
| Period | 3 |
| Block | p-block |
| Phase at STP | Gas |
| Density | 0.002 g/cm³ |
| Melting point | 83.81 K (-189 °C) |
| Boiling point | 87.3 K (-186 °C) |
| Electron configuration | [Ne] 3s² 3p⁶ |
| Crystal structure | Face-centered Cubic |
| Discovered | 1894 |
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See Ar in context with all 118 elements.
Working with argon in a real design?
Ask the materials chat how Ar behaves in your alloy system, what it does to weldability, and which grades to look at — with the source of every number named.