I racked my brain for almost 10 minutes, until suddenly,
it hit me !
You're breathing one right now ! So am I .
Air is a mixture of a lot of elements.
Nitrogen, Oxygen, and Argon account for 99.964 percent.
The other 0.036 percent is mainly Neon, Helium, Krypton,
and Hydrogen ... more elements.
Then there are Carbon Dioxide and water vapor.
Yes, those are compounds. But together, they add up
to very little of the air we breathe, and if both of them
suddenly disappeared, we would hardly notice it.