Explanation of alpha scattering experiment

Alpha particles which are made up of 2 protons and 2 neutrons (overall positive charge) are fired towards a thin sheet of gold. To ensure any deflection of the alpha particles is only due to the gold sheet the experiment is conducted in a vacuum. It was predicted that all the alpha particles would pass straight through the gold foil. In fact it was found that some alpha particles were deflected and the direction of some of the particles was completely reversed, however most of the particles did pass through the foil. The conclusions of this experiment were:

1. Most of an atom is empty space - Evidence of this is that most the particles passed through the gold foil.
2. The large defection/repulsion of a small number of the positively charged alpha particles suggests there is an area of concentrated positive charge (must be positive because like charges repel) in each atom - this was later described as the nucleus.
3. The very small number of alpha particles being deflected straight back indicates that the positive charge and mass of each atom are concentrated into a tiny volume relative to the size of each atom.

These conclusions led on to the nuclear atomic model.