is rather uncreative in its normal gaseous form - lightning can combine
it with things, but otherwise it does nothing naturally. When you see
'packed in a protective atmosphere' on something, it often means
nitrogen. The nitrogen cycle is biologically driven. More reactive gases like oxygen and hydrogen will combine with other
things and be lost to the atmosphere (apart from carbon dioxide and
monoxide). And the least dense gases (hydrogen and helium) will be lost
to space. Nitrogen also has low solubility in water, unlike oxygen, and
the amount contained in the oceans will be very small. There is quite a
lot of oxygen dissolved in the surface waters of the Earth. When you
think about it, there's a heck of a lot of oxygen and hydrogen tied up
in all that water as well... Not to mention the amounts tied up in
organic matter, where nitrogen is a vital but much smaller participant
When the earth was formed all gases were present in a condition of equilibrium.
However, nitrogen is present most abundantly now because it cannot be used directly without nitrogen fixation which occurs at a very small scale.
Also it belongs to the fifth group in the periodic table due to which it is less reactive as compared to the other gases e.g. Oxygen.
Here is a free answer: As the earth formed, that was the equilibrium condition of the constituent molecules.
I hope you ask a follow up question.