Why do electrons have negative charges?
Because electronic particles were ASSIGNED this charge...........
Matter consists of electrons, fundamental particles of negligible mass with unit electronic charge, that are conceived to orbit round a massive nuclear core which consists of
There is nothing fundamental in the current designation; protons and electrons simply have OPPOSITE signs to their electronic charge. For quantum chemists, there have been generations of punters who got the right magnitude on their calculations of many electron atoms, BUT the wrong sign, simply because they counted the number of electrons wrongly and got odd instead of even or even instead of odd.