Rutherford - Gold Foil Experiment - Backstage Science

While most did pass through, Rutherford was shocked to find that:

At the time, scientists believed in the , where an atom was a blob of positive charge with electrons scattered inside like fruit in a pudding. If this were true, the heavy alpha particles should have whizzed straight through the "soft" atoms.

Positively charged particles emitted from a radioactive source (radium).