Why did Rutherford choose ‘Gold foil’ to perform ‘Alpha particle
scattering experiment’?
Answers
For the scattering experiment, Rutherford wanted a metal sheet which could be as thin as possible. Gold is the most malleable of all known metals. It can easily be converted into very thin sheets. Hence, Rutherford selected a gold foil for his α-particle scattering experiment.
Heavy nuclei have large positive charges and light nuclei have small positive charges. The repulsion between alpha particles and heavy nuclei is much larger than the repulsion between alpha particles and small nuclei.
More number of alpha-particles will pass as the nucleus of the lighter atoms is small, a smaller number of alpha-particles will be deflected as many positive charges are less than on the lighter nuclei.
So if he were to take a lighter material foil, like aluminium, the nucleus will be pushed out on contact with the particles. But if the foil was too heavy, the particles will not be able to pass through it.
Gold seemed to be the best as it was neither too light nor too heavy, and it is the thinnest foil known, so Rutherford used it for his experiment.