Ernest Rutherford

It was almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you.

It is just as surprising as if a gunner fired a shell at a single sheet of paper and for some reason or other the projectile bounded back again.

Radioactivity is shown to be accompanied by chemical changes in which new types of matter are being continually produced. … The conclusion is drawn that these chemical changes must be sub-atomic in character.