Ionizing radiation

Ionizing radiations are those that have enough energy to remove an electron from the atom when they interact with it, this phenomenon is known as ionization, hence the name of this type of radiation.

The atom and ionizing radiation

If we want to understand what ionizing radiation is, we have to delve into the smallest unit of a chemical element that maintains its identity or its properties and cannot be divided by chemical processes: THE ATOM.

The atom is formed by a nucleus, composed in turn by protons and neutrons and by a shell that surrounds it, in which the electrons are found. The subatomic particles that make up the atom cannot exist in isolation except under very special conditions..

  • The proton was discovered by Ernest Rutherford at the beginning of the 20th century. It is an elementary particle that constitutes part of the nucleus of any atom. The number of protons in the atomic nucleus, called the atomic number (Z), is what determines the chemical properties of the atom in question. Protons have a positive electrical charge and a mass 1,836 times greater than that of electrons.
  • The neutron, an elementary particle that constitutes part of the nucleus of atoms, was discovered in 1930 by two German physicists, Walter Bothe and Herbert Becker. The mass of the neutron is slightly higher than that of the proton, but the number of neutrons in the nucleus does not determine the chemical properties of the atom, although it does determine its stability against possible nuclear processes (fission, fusion or radioactivity emission) as we will see later. . Neutrons have no electrical charge and are unstable outside the nucleus, disintegrating to give a proton, an electron, and an antineutrino. The number of protons plus the number of neutrons in the nucleus of an atom is the mass number (A).
  • The electron was discovered in 1897 by J. J. Thomson. The mass of the electron is 1836 times less than that of the proton and it has the opposite charge, that is, negative. The electrons move in diffuse orbits surrounding the nucleus at different distances from it, according to the energy they possess, to form the atomic diameter. These distances are enormous compared to the size of the nucleus, so that for an element of medium atomic diameter, if we consider its nucleus to be the size of a walnut, the electron cloud may have the dimensions of a football stadium. Under normal conditions, an atom has the same number of protons as electrons, which makes atoms electrically neutral entities. If an atom gains or loses electrons, it becomes an ion.

What is an isotope?

Each chemical element has a fixed number of protons, but its number of neutrons can vary, so that the same element can exist in nature with a different proton/neutron ratio in its nucleus, they are called isotopes.

Therefore isotopes are atoms of the same element, whose nuclei have a different number of neutrons and, therefore, differ in mass. Most chemical elements have more than one isotope. Only 21 elements (examples: beryllium, sodium) have a single natural isotope; in contrast, tin is the element with the most stable isotopes (10 isotopes are known).

Other elements have natural isotopes, but are unstable, since they have a number of neutrons greater or less than the number of protons in the nucleus. The figure shows the carbon atom (C) as an example. The C-12 and C-13 are stable isotopes, while the others (C-9, C-10, C-11, C14, C15 and C-16) are unstable isotopes of carbon.

Unstable nuclei, with excess energy, always tend to stabilize, so sooner or later they release excess energy, undergoing a transformation (or disintegration). Thus, during the transformation, a large amount of energy is released in the form of ionizing radiation, this phenomenon being known as radioactivity.

Types of Ionizing Radiation


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