Saturday, 17 January 2015



Radioactivity is the phenomenon whereby some nuclei, not stable, are transformed into other emitting particles. Radioactivity was not invented by man, but on the contrary, man is exposed to radioactivity from the moment of its appearance on Earth. The radioactivity is as old as the universe and is present everywhere: in the Stars, in the Earth even in our own bodies.

The discovery of radioactivity occurred to the 800 by Henry Becquerel and Marie Curie spouses, who received the Nobel Prize for Physics for their research. They discovered that some minerals, uranium and radio, had the property of impressing photographic plates placed in their vicinity. Photographic plates, once developed, had dark spots.

Elements such as uranium, radium and polonium were referred to as "active" and the phenomenon of particle emission was told radioactivity. They have since been identified nearly 2,500 species of different nuclei, and only a small percentage of them, about 280, are stable.

Origin of Radioactivity

Radioactive isotopes can be natural or artificial origin. However one must not think that the natural radioactivity and artificial phenomena are different, since the physical process at the base is the same for both.

The natural radioisotopes have originated at the center of the stars, through nuclear reactions or during the explosions of supernovae. Some of these nuclei, such as potassium-40 (40K), thorium-232 (232Th) and uranium-235/238 (235U / 238U) are still active, as their half-life is several billion of years. The measurement of the abundance of these isotopes remaining on Earth can be traced back to the age of our planet, which is calculated in 4.5 billion years.

The artificial radioactive nuclei were created in the laboratory or in nuclear reactors.

The Radioactivity In Nature

The radioactivity is a natural phenomenon: for this reason anything on Earth, including our bodies, contains a certain percentage of radioactive elements.

The radioactivity in the air is due to the presence of radon (Rn). This element is produced by the decay of uranium and thorium, which are found in many materials, especially in the rocks. As gas, radon is able to "evaporate" spreading in the air. In 1,3 of air in a closed building occur on an average 30 radon