Why is nitrogen the solvent of air?

Answer 1

Solvents can be gases, liquids, or solids. Usually, the substance present in the greatest amount is considered the solvent, which in the case of air is nitrogen. Air is a gaseous solution of oxygen and other gases dissolved in nitrogen. In many ways, air behaves like ideal gases over the normal pressure and temperature range. Thus the molecules in air are "bouncing around freely", rather than forming the sort of chemical bonds that characterize solutions.

As to the aspect why is there a lot of nitrogen? Well, I'd guess it is a function of the age of the universe, as the heavier elements tend to be formed by nuclear fusion in stars, which are then dispersed again when stars go supernova. It is also a function of reactivity, as oxygen is the most common element by weight in the Earth's crust. Nitrogen being more inert is not tied up to the same extent in compounds. Lighter gases like hydrogen would escape the Earth's gravity. Temperature is kinetic energy on the molecular scale and lighter molecules travel on average faster than heavy molecules to have the same average kinetic energy: thus they also reach escape velocity at lower temperatures.

Answer 2

Nitrogen is the most abundant gas in air, making up about 78%. It is not considered a solvent but rather a main component of air because it is non-reactive and stable under normal conditions, providing a stable mixture for other gases and molecules to exist in.