Solid, liquid, and gas from least to most dense

gas, liquid, and then solid

Explanatioson:

Solids are typically going to be more dense; the molecules are more tightly packed together than in a liquid or a gas. Solids have a higher density. Liquids are more free-moving and the molecules do not hold on so tightly to each other, hence the lower density. Gases are completely free-moving and have a much lower density than the other two

oxygen = 21% of the atmosphere

nitrogen = 78%

carbon dioxide = 0.1%

argon =0.934%