At the end of the 19th century Thomson and Rutheford studied the phenomenon of the ionisation of gases illuminated with the rays discovered by Becquerel. During the experiment Rutheford discovered that there were two kinds of such radiation: The first one called the alpha rays was easily absorbed even by paper; the second one called the beta rays could penetrate through even thick metal brasses like for example 0.25 centimetres of aluminium. Soon the third kind of radiation was discovered. It had high penetrating power - it could go through even a couple of centimetres thick layers of lead. This third kind of radiation was called the gamma rays.
A few next years scientists spent explaining the nature and properties of those three kinds of radiation.
The alpha rays (having low penetrating power) consist of positively charged particles - in a magnetic field, and in an electric field alpha rays are deflected in the same direction as other positively charged particles. It turned out that the ratio q/m (charge to mass) of the alpha particles is two times smaller than q/m of hydrogen nuclei. Scientists concluded that alpha particles are helium nuclei whose mass equals 4*(hydrogen mass), and whose positive charge equals 2*e. As you know the helium nucleus consists of two protons and two neutrons.
The beta particles (having much higher penetrating power) can be deflected in a magnetic field, and in an electric field, and the deflection direction shows that they are charged negatively. In the further study it turned out that they are simply electrons.
Different radioactive elements emit different amounts of those three kinds of radiation.
There are three basic kinds of radiation - alpha, beta, and gamma.
The alpha rays are helium nuclei.
The beta rays are electrons.
The gamma rays are photons having high energy.
What are the nuclear transformations?