Theory
Scattering
Atoms
αβγ decay
Decay Series
Law
Half-life
Geiger
Carbon-14
Fission
Chain Reaction
Nuclear Energy
Nuclear reactors
Fusion

Two of Rutherford's students, Geiger and Marsden, performed the alpha scattering experiment.

Rutherford said "...it was as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you."

Rutherford's interpretation of the results, revolutionised our understanding of science.

He recognised that the atom was largely empty space, with a nucleus at the centre.

This was the first real insight into atomic structure.


In 1911, Ernest Rutherford and some of his students directed
-particles at a thin gold foil. They placed a zinc sulphide screen near enough to the foil to detect any alpha particles that got through.


of -scattering


The zinc sulphide would give off a flash of light whenever struck by an -particle. They expected that the -particles would go right through the foil with hardly any deflection because in the Thomson model, the positive and negative electric charges inside an atom were assumed to be uniformly distributed through a solid atom. Consequently the positively charged -particles would only encounter weak electric forces and so pass through the thin foil with only slight
deflections (less than a degree).

           Thomson model                    Rutherford model           
     -particles undeflected             -particles scattered


Rutherford and his associates found that although most of the
-particles were not deviated by much, a few were deflected through very large angles and some were even deflected in the backward direction. As Rutherford remarked, "It was as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you."
                                   
Rutherford’s explanation of this remarkable finding was that an atom must not be solid, but in fact largely empty space surrounding a tiny nucleus, in which its positive charge and nearly all its mass are concentrated, with electrons some distance away. With this sort of atom, it is easy to see why most alpha particles go right through a thin foil. However, when an -particle comes near a nucleus, the intense electric field there causes it to be scattered through a large angle and possibly even backwards.

More Information

Rutherford's Work
Rutherford scattering experiment