|In situ availability:|
|F ← Ne → N/A|
|Cl ← Ar → K|
|Br ← Kr → N/A|
|Atomic radius (pm):||71|
|Bohr radius (pm):||71|
|Covalent radius (pm):||97|
|Van der Waals radius (pm):||188|
|ionic radius (pm):||-|
|1st ion potential (eV):||15.76|
|Electrons Per Shell|
|2, 8, 8|
|Electron Affinity:||Unstable anion|
|Crystal structure:||Face centered cubic|
Argon is a Noble gas in group 18.
It has a Face centered cubic crystalline structure.
This element has 3 stable isotopes: 36, 38, and 40.
Most of the volatiles have been deposited in the top layers of the Moon's surface by the solar wind over geologic time. A notable exception to this is Argon. The concentration of Argon in lunar soil is much higher than found in the solar wind, so must come from a different source. Especially, the isotope Argon-40. It is presently believed that the Argon-40 comes from radioactive decay of Potassium-40 deep within the lunar mantle or core, and that the Argon-40 seeps out to the surface via fissures. This lunar outgassing continues today. This vented Argon enters the lunar atmosphere; then the Argon is implanted into the regolith by interactions with ions from the solar wind.
Public domain info obtained from NASA:
Moon Fact Sheet
Lunar Atmosphere Estimated Composition (particles per cubic cm):
- Helium 4 (4He) - 40,000
- Neon 20 (20Ne) - 40,000
- Hydrogen (H2) - 35,000
- Argon 40 (40Ar) - 30,000
- Neon 22 (22Ne) - 5,000
- Argon 36 (36Ar) - 2,000
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