So here I will ask some really stupid questions about quantum theory. I'll dribble them out, one by one, and fully expect either derision or elementary responses from our resident experts. So. I took chemistry in college when dinosaurs roamed the Earth, and this is what I recall. Obviously the electron is a charged extra-nuclear particle, with, I assume mass. How come mass? The nucleus, as I was taught, comprised protons (with mass and charge), neutrons (with mass but no charge) and neutrinos (mass, and no charge). They also said said there was bunch of other stuff I wasn't to bother my pretty head about; we'll come to that So here is my first embarrassing question: You guys talk about particle "mass" using units of electron volts eV. So how can a particle without charge but with so-called mass be described in these terms?