Actually, earth's atmosphere is 78% nitrogen, 21% oxygen, 0.9% argon, and 0.03% carbon dioxide.

It also contains water vapor

I know it's not MOSTLY water but it's still made up of that element along with several other gases. But since I was talking about water, I didn't see the point in mentioning Nitrogen

Bu thanks for correcting me, the smaller the spread of misinformation the better.