Work Step by Step
Nearly all the alpha particles made it through with little deflection, indicating that the nucleus is mostly empty space. A very small fraction of the positively-charged alpha particles were deflected (scattered) through a large angle, almost straight backward, with little change in speed. This indicates that the positive charge inside the atom must be concentrated in a small central region, the nucleus, which contains most of the atom’s mass. This is discussed on pages 603-604.