[matea]

i would really like to know why is there so much argon in the air, and for example not xenon,,,
did argon appear in atmosphere because of some radioactive decays in past or?

i would be really thankful for any answer:)

[Borek]

did argon appear in atmosphere because of some radioactive decays in past or?

Honestly I don't know, but

http://en.wikipedia.org/wiki/Potassium-argon_dating

argon is produced when ⁴⁰K decays. WHat is more important, Ar is too heavy to leave the atmosphere, so it stays with us.

That's only my guess.

[woelen]

The relative ratio's in which elements are present is already determined very long ago, before the sun and the planets around it were formed. Current scientific view is that the sun and planets are formed from gas and dust, which are the remnants of a supernova explosion, a long time ago.

In a supernova explosion, fusion of lighter elements gives the heavier elements. But, from iron and higher, fusion costs energy and for the heaviest elements, a lot of energy has to be put in it. Argon is a lighter noble gas than xenon and that explains why it is more abundant. Helium and neon are more abundant, but not on earth. They have escaped atmosphere long ago, due to the relative lightness of molecules.

[Borek]

The relative ratio's in which elements are present is already determined very long ago, before the sun and the planets around it were formed. Current scientific view is that the sun and planets are formed from gas and dust, which are the remnants of a supernova explosion, a long time ago.

While that's not completely incorrect, I don't think it is 100% correct either. Helium that you can buy is obtained form natural gas. All helium that was pesent in the initial mixture that finally become Earth was long gone before the planet solidified. The only source of the helium that later allowed to build up its presence in the natural gas is natural radioactivity. No idea how it was with argon.