2. Classes of radioactivity

alpha

It is a type of slightly penetrating radiation that can be stopped by a simple leaf of paper. Rutherford suggested that the beams alpha are ions of atoms of Helium (He2 +) moving rapidly, and in 1909 it demonstrated it experimentally.
This type of radiation is issued by cores of heavy elements placed at the end of the periodic table (A> 100). These cores have many protons and the electrical repulsion is very strong, for what they tend to obtain N approximately equally to Z, and for it a particle issues alpha. In the process there becomes detached a lot of energy that turns into the kinetic energy of the particle alpha, that is to say that these particles go out with very high speeds.

RADIATION THREAD
It appears for any type of core, but it is typical of cores with excess of neutrons, that is to say N> Z. It is a mechanism used by the cores to come to the line of stability (N approximately equal Z)
The radiation Thread - consists of the spontaneous emission of electrons on the part of the cores, but in the core only there are protons and neutrons, how can it issue electrons? In 1934 Fermiexplicó this radiation supposing that in the disintegration thread less, a neutron transforms in a proton, an electron and an antineutrino by means of the reaction:
N0----> p + + and - + antineutrino

Radiation gamma
In this type of radiation the core does not lose his identity. By means of this radiation the core parts with the energy that it exceeds him to go on to another condition of lower energy. It issues beams gamma, or very energetic photons. This type of emission accompanies on the radiations alpha and thread.
It is a very penetrating radiation, crosses the human body and only it is stopped by plates of lead and thick walls of concrete. To the being so penetrating and so energetic, of three types of radiation it is the most dangerous.