Argon Argon Argon is a chemical element with symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in the Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as abundant as water vapor (which averages about 4000 ppmv, but varies greatly), 23 times as abundant as carbon dioxide (400 ppmv), and more than 500 times as abundant as neon (18 ppmv). Argon is the most abundant noble gas in Earth's crust, comprising 0.00015% of the crust. Nearly all of the argon in
Trace gas causes its strong absorption of infrared radiation. Below is a table of some of the major greenhouse gases with man-made sources and their contribution to the enhanced greenhouse effect. Key Greenhouse Gases and Sources In contrast, the most abundant gases in the atmosphere are not greenhouse gases. The main reasons is because they cannot absorb infrared radiation as they do not have vibrations with a dipole moment. For instance, the triple bonds of atmospheric dinitrogen make for a highly symmetric molecule that is very inert in the atmosphere. The residence time of a trace gas depends on the abundance and