Question

rutherfords famous gold foil experiments shot heavy particles at a thin sheet of gold foil. what did he observe, and why did these observations eventually result in the addition of a nucleus to the atomic model?
some of the heavy particles bounced off the foil because there are positive particles spread throughout the atom
some of the heavy particles bounced off the foil because there is a dense positive area in the atom.
the heavy particles all passed straight through the foil because the atoms are mostly empty space
the heavy particles all bounced off the foil because the subatomic particles have mass and volume.

Explanation:

In Rutherford's gold - foil experiment, most particles passed through, but some bounced back. This indicated the presence of a small, dense, positively - charged region (the nucleus) in the atom. Positive particles spread throughout the atom was Thomson's plum - pudding model idea. All particles passing straight through doesn't explain the addition of a nucleus. All particles bouncing off isn't what was observed.

Answer:

Some of the heavy particles bounced off the foil because there is a dense positive area in the atom.