The most abundant elements in the air are:
Nitrogen, Oxygen
The air (on ground level, not in a traffic jam!) is composed of ~80% N2, ~20% O2, 0-6% H2O (vary a lot), 0.03% CO2, 1% argon and then traces of other elements. The most abundant element is thus...
Air is made up of: 78% Nitrogen 21% Oxygen1% Argon ppm levels of several other gases
Hydrogen
The ratios are about 78% nitrogen, 21% oxygen, 1% argon, and .04% carbon dioxide