Which Alpha Particles Passed Straight Through The Gold Atoms?

Some will... But some will not. This is part of a classic physics experiment that led to the discovery of the nucleus. Ernest Rutherford conducted this experiment by shooting alpha particles at a thin sheet of gold (gold foil). He fully expected them to pass straight through or be deflected at a small angle, but to his surprise some came straight back. Some were also deflected at small angles and some pass straight through unchanged. He said the fact that some came back was like shooting a larger artillery shell at a tissue paper and having the shell bounce back at you.

This experiment led him to hypothesize that there must be a large massive nucleus at the center of atoms.