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Argon is a chemical element; it has symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. [10] Argon is the third most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv).
Argon (18 Ar) has 26 known isotopes, from 29 Ar to 54 Ar, of which three are stable (36 Ar, 38 Ar, and 40 Ar). On Earth, 40 Ar makes up 99.6% of natural argon. The longest-lived radioactive isotopes are 39 Ar with a half-life of 268 years, 42 Ar with a half-life of 32.9 years, and 37 Ar with a half-life of 35.04 days.
For large-scale use, helium is extracted by fractional distillation from natural gas, which can contain up to 7% helium. [80] Neon, argon, krypton, and xenon are obtained from air using the methods of liquefaction of gases, to convert elements to a liquid state, and fractional distillation, to separate
The nuclides found naturally comprise not only the 286 primordials, but also include about 52 more short-lived isotopes (defined by a half-life less than 100 million years, too short to have survived from the formation of the Earth) that are daughters of primordial isotopes (such as radium from uranium); or else are made by energetic natural ...
The term phase is sometimes used as a synonym for state of matter, but it is possible for a single compound to form different phases that are in the same state of matter. For example, ice is the solid state of water, but there are multiple phases of ice with different crystal structures , which are formed at different pressures and temperatures.
Argon compounds, the chemical compounds that contain the element argon, are rarely encountered due to the inertness of the argon atom. However, compounds of argon have been detected in inert gas matrix isolation, cold gases, and plasmas, and molecular ions containing argon have been made and also detected in space.
"The brines provide an environment in which elements and simple organics could have combined to form more complex prebiotic organics on the pathway to life," said geologist Tim McCoy, curator of ...
Solid argon-hydrogen clathrate (Ar(H 2) 2) has the same crystal structure as the MgZn 2 Laves phase. It forms at pressures between 4.3 and 220 GPa, though Raman measurements suggest that the H 2 molecules in Ar(H 2) 2 dissociate above 175 GPa. A similar Kr(H 2) 4 solid forms at pressures above 5 GPa. It has a face-centered cubic structure where ...