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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).
The excimers used for lasers may be noble gas dimers such as Ar 2, Kr 2 or Xe 2, or more commonly, the noble gas is combined with a halogen in excimers such as ArF, KrF, XeF, or XeCl. These lasers produce ultraviolet light, which, due to its short wavelength (193 nm for ArF and 248 nm for KrF), allows for high-precision imaging.
Bracketed noble gas symbols on the left represent inner configurations that are the same in each period. Written out, these are: He, 2, helium : 1s 2 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 ...
Noble gas configuration is the electron configuration of noble gases. The basis of all chemical reactions is the tendency of chemical elements to acquire stability . Main-group atoms generally obey the octet rule , while transition metals generally obey the 18-electron rule .
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.
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.
Structure of a noble-gas atom caged within a buckminsterfullerene (C 60) molecule. Noble gases can also form endohedral fullerene compounds where the noble gas atom is trapped inside a fullerene molecule. In 1993, it was discovered that when C 60 is exposed to a pressure of around 3 bar of He or Ne, the complexes He@C 60 and Ne@C 60 are formed ...
2 is then condensed into a noble gas matrix, either a pure element or a mixture. Heavier noble gas atoms will tend to displace the lighter atoms. Ionic molecules produced this way include UO 2 Ne 4 Ar +, UO 2 Ne 3 Ar + 2, UO 2 Ne 2 Ar + 3, UO 2 NeAr + 4, UO 2 Ar + 5, UO 2 Ar 4 Kr +, UO 2 Ar 3 Kr + 2, UO 2 Ar 2 Kr + 3, UO 2 ArKr + 4, UO 2 Ar 4 ...