Now watch the following video.
Radioactivity was discovered in 1896 by Henri Becquerel who noticed that the radiation from uranium salts had similar characteristics to X-rays that had been discovered the previous year by Wilhelm Röntgen. The uranium salts emitted particles that reacted with photographic plates.
Over the following 20 years, Marie and Pierre Curie, Ernest Rutherford, and many others worked on identifying the different emissions called initially ‘uranic rays’. Marie Curie was working with a uranium ore called pitchblende, and managed to isolate two new elements within the pitchblende – polonium and radium. This was no mean feat as within a tonne of pitchblende there was less than a gramme of these new, highly radioactive elements.
It was discovered that radioactive materials emit particles of three distinct types and that these had differing masses and charges. These three types of emission were called alpha, beta and gamma particles.
You’ll look at these particles in the next section.