What did Rutherford's gold foil experiment show?

The results of this experiment gave Rutherford the means to arrive at two conclusions: one, an atom was much more than just empty space and scattered electrons and two, an atom must have a positively charged center that contains most of its mass (which Rutherford termed as the nucleus).

The gold foil experiment demonstrated (according to Rutherford) that most of an atom is empty space (therefore 99.995% non-reflected α-particles) with a very small positively charged nucleus in the middle (responsible for deflecting 0.005% of all α-particles).

Rutherford’s associates bombarded a very thin (##10^(-7)## m) gold foil with α-particles.

Au-nucleus [##p^+ =79, n^0 = 118##]; α-particle [##p^+ = 2, n^0 = 2##] is ##He^(2+)##, positive electric charge

The result was 99.995% α-particles were not deflected (1 in 20,000 α-particles were turned through an average angle of 90 degrees in passing through a layer of gold-foil about 0.00004 cm thick).

This proved that atoms had an inner core that contained most of the mass of an atom and was positively charged. It led to what we now call the nuclear model of the atom.

See http://myweb.usf.edu/~mhight/goldfoil.html