Composition of Earth's Atmosphere by Mass

It's 23.19%..

timur-

Thank you.

What is your source?

I made the final calculation based on these numbers:

Source

timur-

Thank you.

So, in that earth's atmosphere is a lower percentage (20.95%) by volume than by mass (23.19%), therefore oxygen is heavier than air, and therefore the oxygen tends to stay in the lowest part of the atmosphere closest to the surface of the earth. If the numbers were reversed then oxygen would be lighter than air, and therefore would tend to rise well above the surface of the earth and thus not be available to initiate life on earth.

Is that true?