Radioactivity

Radioactivity is the characteristic emission of ionising radiations by unstable nuclei.

When the ratio of protons to neutrons in an atom is not adequate, the nucleus becomes unstable and, in attempting to reach stability, may spontaneously disintegrate, emitting radiations. In this way it is transformed into a different nucleus which may either still be radioactive, in which case the process of disintegration continues, or be stable, in which case the reaction stops.

The energy emitted in the disintegration of an atom may be propagated as electromagnetic radiation or in the form of particles. A distinction is made between the following:

• Alpha radiation: particulate and with a low power of penetration. This type of radiation may be detained with just the thickness of a sheet of paper.
• Beta radiation: particulate and with a higher penetration power, although a sheet of aluminium is sufficient to detain it.
• Gamma radiation: electromagnetic waves with a very high power of penetration. To detain this type of radiation a lead barrier of a certain thickness is required.

The half life is the time period required for half the unstable nuclei of a radioactive substance to decay. This period may range from thousandths of a second to millions of years, depending on the radioactive substance in question.

Ionising radiations have sufficient energy to strip electrons from the atoms in the medium through which they pass, possible causing physical-chemical and structural changes in it.

Most ionising radiations are of natural origin and cone mainly from the sun and minerals in the Earth’s crust. Only 12% of the radiations that we receive are artificial in origin.

Science and technology have allowed mankind to discover and develop a practical use for the phenomenon of radioactivity. For some time now, ionising radiations have found applications in the field of medicine, where they are used in treatment and diagnosis, in industry, for the measurement of thicknesses and densities, in the field of archaeology, for the dating of deposits, in the generation of electricity in nuclear power plants, etc.