The presenters recap on atomic structure by defining an element's atomic number and mass number. They then use protons and neutrons to make a model of a francium nucleus. The nucleus is unstable and starts to decay. The presenters point out the three different types of radiation that are being emitted.

First broadcast:
21 November 2008

This clip could be used by students as an introduction to radioactivity. The clip needs to be used in conjunction with 'Introduction to radioactivity (pts 2/3 and 3/3)'.