Question

Why was the thinness of the gold sheet employed in Rutherford's famous experiment significant in Rutherford's interpretation of atomic structure?

Answer 1

All metals are malleable. Gold is extremely malleable among metals. What does malleable mean?

Explanation:

Malleable means that the material is capable of being hammered out into a sheet (cf. malleus , Latin for hammer). This malleability (this workability) is one of the reasons why gold is prized for jewellery and ornamentation. The other reasons why are that gold is beautiful, and it doesn't tarnish readily. Gold can be hammered out into a sheet only a few atoms thick - which I think is phenomenal. When Rutherford fired `alpha` particles at his thin gold sheet, most of the particles passed straight through the sheet without deflection. A few were deflected, and a smaller few bounced straight back at the `alpha` particle emitter.

This last result was astounding (on the basis of the thinness of the gold foil). To quote 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. On consideration, I realized that this scattering backward must be the result of a single collision, and when I made calculations I saw that it was impossible to get anything of that order of magnitude unless you took a system in which the greater part of the mass of the atom was concentrated in a minute nucleus. It was then that I had the idea of an atom with a minute massive centre, carrying a charge.Source

Rutherford could only account for the results he observed by proposing a nuclear core that contained most of the mass of the atom, and ALL of the positive charge. The nuclear age was born.