So I understood, initially, that the scale of amu(atomic mass unit) is based upon 1/12 the mass of carbon-12. This made sense to me until another section in my textbook listed the mass for Electrons, protons, and neutrons. So we know that carbon-12 has 6 protons, and 6 neutrons. Now we also know that the mass of a proton and a neutron are both greater than 1, this is greater than 12 without even factoring in the mass of electrons(negligible). Here is my math below.
6*Mass of Proton + 6*Mass of neutron
6*1.0072764669amu + 6*1.0086649156amu > 12 amu
So without even factoring in the electrons we are over 12amu for one atom of carbon-12. To me this says one of these principles is violating the definition of the other. No one I ask can explain why this happens, and what the real rule is. Can anyone explain why these numbers don't agree? My book doesn't see the need to explain an obvious contradiction. Thanks.