Key Stage 4
Meaning
The Nuclear Model is a model of the atom which suggests there is a positively charged nucleus in the centre of an atom with electrons orbiting around the nucleus.
About the Nuclear Model
- The Nuclear Model was first proposed by Ernest Rutherford after he successfully disproved the Plum Pudding Model of the atom using his alpha scattering experiment.
- In the Nuclear Model most of the atom is empty space. The majority of the mass of the atom is concentrated in a small central nucleus. This central nucleus has a strong positive charge while negatively charged electrons orbit the nucleus.
Evidence for the Nuclear Model
- In Rutherford's Alpha Scattering Experiment several observations about the path of alpha particles through a thin sheet of Gold foil that led to the development of the Nuclear Model:
Observation | Conclusion |
Most of the alpha particles pass straight through the foil. | The atom must be mostly empty space. |
Some of the alpha particles were deflected by a small angle. | The mass of the atom must be concentrated in an extremely small volume in the centre. |
A very small number of alpha particles came back in the direction of the detector. (Deflected more than 90°.) | The centre of an atom must have a strong positive charge.
The electrons must not be in the centre of the atom, they must be orbiting the nucleus. |
hey discovered that most of the alpha particles went through in a straight line. A significant number were deflected and a very small number bounced off the Gold back towards the alpha source.