What are ways to find mass?

The method used to find atomic mass depends on whether you're looking at a single atom, a natural sample, or a sample containing a known ratio of isotopes:

Look Up Atomic Mass on the Periodic Table If it's your first encounter with chemistry, your instructor will want you...

Sum of Protons and Neutrons for a Single Atom To calculate the atomic mass of a single

beta is electron from nucleus

something from nucleus has changed, but charge must be same for cons of charge