(N2 & O2 & Ar & CO2...)
an element compound or mixture?

Mixture

Explanation:

Element is a pure substance which is composed of atoms of similar elements.

Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.

Mixture is a substance which has two or more components which do not combine chemically and do not have any fixed ratio in which they are present. Example: Air which conatins a mixture of , , and