Radioactivity 5

A diagram to show the scattering of alpha particles

Geiger and Marsden were scientists who carried out an experiment to find out more about atoms.  They fired alpha particles from a radioactive source at a very thin piece of gold foil which was only one atom thick.  They used a detector to find out where the alpha particles went after travelling through the foil.  The experiment was carried out in a vacuum because air particles stop alpha particles travelling very far.

Observation ---------------> Conclusion

• Most alpha particles went straight through -------> Most of an atom is empty.
• A few alpha particles are deflected by a small angle ----> The nucleus must be positive because it repels the alpha particles.
• Occasionally an alpha particle is deflected through an angle greater thna 90. ----> The nucleus is veyr small indeed as very few alpha particles get close to the nucleus.

Factors affecting the deflection of alpha particles

1) charge on the nucleus - the greater the charge on the nucleus the…