The neutron and proton masses are both close to 940 MeV/c^2. [Neutron is actually slightly heavier.] The electron is 0.512 MeV/c^2. So, it takes ~2000 electron masses to make a nucleon mass. Since the most massive element has only slightly more than 100 electrons, the electron mass is always negligible compared to nuclear mass (in chemistry.) The biggest variation in nuclear masses actually come from averaging isotope species and (to a much smaller extent) differences in binding energy.
Thanks, again, Dr. That helps push me past the electron weight and significance issue.
Having worked in high-tech communications for decad . . . . . er, a few years, I understand some of the broader concepts of atomic theory and rudimentary physics at about a 50,000 ft. level.
While I’m not the sharpest knife in thew drawer on these issues, I’m always looking for a knife sharperner!!
God I love FR...thanks to all.