>>12935202that's a different question than the two previous questions you asked. people take for granted just how recent atomic theory really is from a scientific background, dating back to just a couple hundred years ago. it started with chemistry, with chemists (alchemists) noticing reactions occurring in proportionate amounts, indicating some fixed rates of reactions with respect to a certain quanta of chemical compound.
in 1897, JJ Thompson discovered the existence of an atom, which was thousands of times smaller than the smallest object known to exist (hydrogen). these electrons were negatively charged and had to be balanced by positive charges, which implied the existence f the nucleus. this is what Ruthrford discovered to exist in the early 1900s.
physicists Bohr, Schrodinger, and others, also in the early 1900s began devising models to describe how these electrons would orbit around such nuclei and be stripped from their orbits in ways that JJ Thompson discovered. it was truly a quantum mechanical description that worked.
yet another notch in favor of quantum mechanics. it's really the crown jewel of modern physics.