Rutherford Scattering
Note how small the nucleus is in relation to the atom: the nuclear radius is 10-14 m versus the atomic radius of 10-10 m - a difference in size of 10,000 and a difference in volume of 1012 (a trillion!).
The electron is even smaller. It is so small that we can’t yet say how small, but it is
less than 10-17 meters in radius.