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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 the 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.
However there are numerous exceptions; for example the lightest exception is chromium, which would be predicted to have the configuration 1s 2 2s 2 2p 6 3s 2 3p 6 3d 4 4s 2, written as [Ar] 3d 4 4s 2, but whose actual configuration given in the table below is [Ar] 3d 5 4s 1.
Ne, 10, neon : 1s 2 2s 2 2p 6 Ar, 18, argon : 1s 2 2s 2 2p 6 3s 2 3p 6 Kr, 36, krypton : 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 Xe, 54, xenon : 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 Rn, 86, radon : 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 10 6p 6 Og, 118, oganesson : 1s 2 2s 2 2p 6 3s 2 3p 6 4s ...
Ar contamination. Most of the argon in Earth's atmosphere was produced by electron capture of long-lived 40 K (40 K + e − → 40 Ar + ν) present in natural potassium within Earth. The 39 Ar activity in the atmosphere is maintained by cosmogenic production through the knockout reaction 40 Ar (n,2n) 39 Ar and similar reactions. The half-life of 39
Argon–argon (or 40 Ar/ 39 Ar) dating is a radiometric dating method invented to supersede potassium–argon (K/Ar) dating in accuracy. The older method required splitting samples into two for separate potassium and argon measurements, while the newer method requires only one rock fragment or mineral grain and uses a single measurement of argon isotopes.
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.
CUO in a solid argon matrix can bind one, or a few argon atoms to yield CUO·Ar, CUO·Ar 3 or CUO·Ar 4. CUO itself is made by evaporating uranium atoms into carbon monoxide . Uranium acts as a strong Lewis acid in CUO [ 87 ] [ 90 ] and forms bonds with energies of about 3.2 kcal/mol (13.4 kJ/mol) with argon.
18 Ar argon; use: 87.302 K: −185.848 °C: −302.526 °F WebEl: 87.3 K: ... Ne 27.104 K (−246.046 °C) 3: Na 1156.090 K (882.940 °C) Mg 1363 K (1091 °C) Al 2743 K