In 1911, Ernest Rutherford proposed the theory that the atom has a central positive nucleus surrounded by negative orbiting electrons. The model he proposed (shown below) shows that most of the mass of the atom was in the center (the nucleus), and the rest of the atom was mostly space. His model was called the "nuclear model."
Rutherford came to this conclusion through his gold foil experiment.
He shot alpha particles (positively charged) through a thin sheet of gold foil and detected them by using screens coated with zinc sulfide and found that while the majority of particles passed through the foil, about 1/8000 were deflected leading to his conclusion that there was much empty space that allowed for most of the particles to pass through, but also a positively charged force that was leading to some of the particles to bounce back (the nucleus).
For a simulation of Rutherford's experiment, watch the video below.
He shot alpha particles (positively charged) through a thin sheet of gold foil and detected them by using screens coated with zinc sulfide and found that while the majority of particles passed through the foil, about 1/8000 were deflected leading to his conclusion that there was much empty space that allowed for most of the particles to pass through, but also a positively charged force that was leading to some of the particles to bounce back (the nucleus).
For a simulation of Rutherford's experiment, watch the video below.
In 1918, Rutherford expanded his theory by finding that he could use alpha particles to knock off small positively charged particles, coinciding with Bohr's model that the nucleus was made up of smaller positively charged particles called protons. This model was called the "proton model."