I don't know if you measure, on a subatomic scale, size by the space it occupies, the mass it has, or what have you; however, most of the particles which we speak of we think of as point charges. While a proton weighs much much more than an electron, an electron is a particle some of the time and a wave some of the time. Actually, it doesn't oscillate between the two; its just that we use a particle to describe its actions some of the time and we use a wave to describe its behavior at other times. I know this doesn't answer your question; I don't know that your question has an answer. How big is a point charge?
