Rutherford

The year 1911 saw yet another atomic model appear, this time by Ernest Rutherford.

Rutherford was investigating J. J. Thomson's atomic model using the [|gold foil experiment]:
 * using a radioactive source of alpha particles, a beam of alpha particles was focused on a thin foil of gold metal.
 * the goal was to see where the mass of the atom was located, since it was known that the atom was mostly empty space.
 * these small deflections were seen, but another unexpected result was found: 1 out of every 8000 alpha particles was "missing".



To find out where these "missing" alpha particles went, he surrounded the gold foil with a detection screen. This screen would illuminate when struck by alpha particles, sometimes at very large angles away from the foil.



Rutherford hypothesized that the particles must be striking something with very high density - a nucleus of positive charge. His new atomic model therefore included a nucleus and he was credited with its discovery.

Watch a modern reconstruction of this experiment in action here:

media type="youtube" key="XBqHkraf8iE" height="315" width="560"

You can visualize all of this by following the link to the gold foil experiment above, and by visiting this [|interactive] site.