How does the atomic mass of oxygen becomes 16??? pls answer ill mark u as brainliest

Atomic mass Of oxygen is 15.99u or 15.99 amu.

And the mass no. Of oxygen is 16 because total no. Of protons and neutrons (in oxygen 16) is 16.

8 protons+ 8neutrons

So we can say that mass no. And atomic mass are different things.

Then, the atomic mass of oxygen is not 16 rather 15.99amu or 15.99u