In Rutherford's gold foil experiment most alpha particles passed straight through the metal foil, but about one in several thousand bounced sharply back toward the source. What conclusion did these results force?

Core Concept

Unimpeded passage shows that nearly all of an atom's volume contains neither mass nor charge able to deflect an alpha particle. The rare violent rebounds require a small region packing the positive charge and nearly all the mass, so head-on encounters are uncommon. Together the observations established the nuclear model and toppled the plum pudding picture.