Breakthrough! Rutherford calculated the small deflection an alpha particle (Helium nucleus from a radioactive element) passing through a very thin foil of a heavy element (gold)
Breakthrough! Rutherford calculated the small deflection an alpha particle (Helium nucleus from a radioactive element) passing through a very thin foil of a heavy element (gold)
The angles are expected to be small, because the positive charge is spread out so the field is relatively small, and while the negative charge is assumed to be concentrated on the electrons, the mass of the electron is 8000 times smaller than that of the Helium, so it can’t push the alpha around much at all. Rutherford designed an experiment to look at these small angles.