Having thought about it after reading here I could have written it a bit better and done a bit more on impact on society.
Rough outline of what I wrote:
* Radioisotopes make a big impact in society
* In medicine they are used for diagnosis and treatment
* e.g. Tc-99m is used for diagnosis of circulation issues etc. as it's a gamma emitter etc
* In industry they are used for many things, e.g. checking thickness or obstructions
* e.g. Am-241 is used to detect smoke particles as it's an alpha emitter
* If we didn't have radioisotopes a lot of things we take for granted would be a lot more difficult and would need complicated electromechanical solutions
I could get 6 or 7 if the markers are nice