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Almost all of the argon in the Earth's atmosphere is the product of 40 K decay, since 99.6% of Earth atmospheric argon is 40 Ar, whereas in the Sun and presumably in primordial star-forming clouds, argon consists of < 15% 38 Ar and mostly (85%) 36 Ar. Similarly, the ratio of the three isotopes 36 Ar: 38 Ar: 40 Ar in the atmospheres of the outer ...
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 ).
The argon found in Earth's atmosphere is 99.6% 40 Ar; whereas the argon in the Sun – and presumably in the primordial material that condensed into the planets – is mostly 36 Ar, with less than 15% of 38 Ar. It follows that most of the terrestrial argon derives from potassium-40 that decayed into argon-40, which eventually escaped to the ...
Argon (symbol Ar) is the third element in group 18, the noble gases. Argon is the third most common gas in the Earth's atmosphere , at 0.93%, making it more common than carbon dioxide . Nearly all of this argon is radiogenic argon-40 derived from the decay of potassium-40 in the Earth's crust.
The decay of 40 K to 40 Ar is used in potassium-argon dating of rocks. Minerals are dated by measurement of the concentration of potassium and the amount of radiogenic 40 Ar that has accumulated. Typically, the method assumes that the rocks contained no argon at the time of formation and all subsequent radiogenic argon (i.e., 40 Ar) was retained.
Where the major source of argon is the decay of 40 K in rocks, 40 Ar will be the dominant isotope. Such locations include the planets Mercury and Mars, and the moon Titan. On Earth, the ratios of the three isotopes 36 Ar : 38 Ar : 40 Ar are approximately 5 : 1 : 1600, giving terrestrial argon a standard atomic weight of 39.948(1).
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The first letter is always capitalized. While the symbol is often a contraction of the element's name, it may sometimes not match the element's English name; for example, "Pb" for lead (from Latin plumbum) or "W" for tungsten (from German Wolfram). Elements which have only temporary systematic names are given temporary three-letter symbols (e.g ...