Rutherford's conclusion
From the observations, Rutherford concluded:
| Label | Observation | Conclusion |
| A | Some alpha particles were deflected by appreciable angles (> 4掳). | There is a concentration of positive charge in the atom 鈥 called the nucleus. Like charges repel, so the positive alpha particles were being repelled by the positive nucleus. |
| B | Most alpha particles went straight through the foil undeflected. | The atom is mostly empty space. |
| C | A very small number of alpha particles were deflected by more than 90掳, with some alpha particles bouncing straight back off the foil 鈥 this is called back scattering. | The nucleus is very small - for back scattering to occur the alpha particle has to have close to a head-on collision with the nucleus of a gold atom. The tiny number of alpha particles being back scattered means the nucleus of the atom is very small compared to the size of the atom as a whole. It also means most of the mass of the atom is concentrated in the nucleus. |
| Label | A |
|---|---|
| Observation | Some alpha particles were deflected by appreciable angles (> 4掳). |
| Conclusion | There is a concentration of positive charge in the atom 鈥 called the nucleus. Like charges repel, so the positive alpha particles were being repelled by the positive nucleus. |
| Label | B |
|---|---|
| Observation | Most alpha particles went straight through the foil undeflected. |
| Conclusion | The atom is mostly empty space. |
| Label | C |
|---|---|
| Observation | A very small number of alpha particles were deflected by more than 90掳, with some alpha particles bouncing straight back off the foil 鈥 this is called back scattering. |
| Conclusion | The nucleus is very small - for back scattering to occur the alpha particle has to have close to a head-on collision with the nucleus of a gold atom. The tiny number of alpha particles being back scattered means the nucleus of the atom is very small compared to the size of the atom as a whole. It also means most of the mass of the atom is concentrated in the nucleus. |
If the plum pudding model had been correct, the Subatomic particle comprising two protons and two neutrons (the same as a helium nucleus). would have passed straight through the foil and not been deflected.
Rutherford had discovered the nuclear All elements are made of atoms. An atom consists of a nucleus containing protons and neutrons, surrounded by electrons., a small, positively-charged nucleus surrounded by empty space (a vacuum) and then a layer of electrons to form the outside of the atom.
The discovery of the make-up of the nucleus (protons and neutrons) came much later, and was not made by Rutherford.
The nucleus was calculated to be about 1/10,000th the size of the atom.