Question

Approximately how much of the total volume of the atmosphere is oxygen?

Answer 1

Around 21%

Explanation:

Earth's atmosphere is approximately 21% oxygen in the form of `O_2`, 78% nitrogen (`N_2`), 1% argon (Ar), and then a trace amount of other gases such as `CO_2` and other noble gases like neon (Ne), xenon (Xe), etc.

I drew up a quick pie chart in Excel for you to have a more visual look at it.