Argon
From Lunarpedia
| Argon | |
|---|---|
| Ar | |
| In situ availability: | |
| Necessity: | |
| Atomic number: | 18 |
| Atomic mass: | 39.948 |
| group: | 18 |
| period: | 3 |
| normal phase: | Gas |
| series: | Noble gases |
| density: | 1.784 g/L |
| melting point: | 83.80K, -189.35°C, -308.83°F |
| boiling point: | 87.30K, -185.85°C, -302.53°F |
| 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 |
| Electron Configuration | |
| 1s2 2s2 2p6 3s2 3p6 | |
| Electrons Per Shell | |
| 2, 8, 8 | |
| Electronegativity: | |
| Electron Affinity: | Unstable anion |
| Oxidation states: | - |
| Magnetism: | Nonmagnetic |
| 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 conitnues 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
http://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html
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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