AS Chemistry help with atomic discovery?

By this elegant experiment he accurately estimated the diameter of the nucleus. He was supposed to have remarked when he got the results of the experiment it was as if he fired bulles at a piece of paper and one of them rebounded!

It showed that the atom was made up of a nucleus very smal and dense containing all the positive charge, surrounded by electrons, found by others notably Bohr arranged in shells around the nucleus

The expt revealed that the atom consisted mostly of empty space with a very small but massive +ve nucleus.

The evidence was that most alphas passed straight through undeviated (about 99.99%!). The rest were scattered thru very large angles (some as much as 180deg). The scattering distribution (proportional to the cosec^4 of the half angle) indicated that the closest approach alphas were moving in a repulsive coulomb field (hence nucleus and alpha had same + charge)

By equating Ek for the 180deg alphas and Ep for the electrostatic potential at the gold nucleus a figure of abt 3x10^-14m was calculated for the coulomb radius of the gold nucleus, about 10^5 times smaller than its atomic radius.

This figure has 2 b revised downwards when the close range attractive nuclear force is taken in2 account- so its nearer 10^-15m.

Incidentally, Geiger and Marsden did the expt and most of the math!