How does the mass of the electron compare to the masses of the proton and neutron?

The mass of protons and neutrons are both 1 amu (atomic mass unit). The mass of the electron is 0.00054. Therefore, when determining the isotopes when given mass, you only focus on the neutrons as they are the subatomic particles that are significantly affecting the atomic mass.

that's what i got you can count the number of atoms