During the $\alpha$-particle scattering experiment, a beam of $\alpha$-particles is directed at a thin sheet of gold foil. The majority of the $\alpha$-particles pass straight through, or are turned through only a small angle. A very small fraction are turned through more than $90^{\circ}$, so they appear to bounce back towards the source of the $\alpha$-particles. Which conclusion about the structure of atoms cannot be deduced from this experiment on its own?
- AMost of the atom is empty space.
- BMost of the mass of an atom is concentrated in the nucleus.
- CThe nucleus contains both protons and neutrons.
- DThe nucleus is charged.