There are three natural radioactive emissions:
- Alpha emission (α): Particles made up of two protons and two neutrons, just like the nucleus of a helium atom. They have an electric charge equal to +2 and a mass equal to 4u;
- Beta emission (β): Particles formed by an electron. They have an electric charge equal to -1 and their mass is considered negligible;
- Gamma emission (γ): It is electromagnetic radiation similar to X-rays. It has no electrical charge and no mass.
These emissions have energy and, therefore, when they are emitted by the nuclei of radioactive atoms (unstable nuclei), they reach the gas molecules, such as those present in the air and able to ionize these gases, that is, they rip off their electrons and form ions.
Ions are atoms of elements that lose or gain electrons and become electrically charged. If an atom loses one or more electrons, it takes on a positive charge and is called a cation. On the other hand, if it gains one or more electrons, it takes on a negative charge and is called an anion.
For example, after being expelled from the atomic nucleus, the alpha particle (24α) collides with oxygen gas molecules (O2) and captures two electrons, turning into a helium atom. Since the O2 lost two, it ionized, generating the ion O2+2.
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24α+O2 → 24He+O2+2
Since the alpha particle has the greatest mass compared to other radioactive emissions, its ionizing power is larger, that is, it extracts electrons from gases more easily and manages to form a greater number of ions per cm3 in its trajectory than other emissions.
The ionizing power of beta particles is medium, because their electrical charge is less than that of alpha particles.
Gamma radiation, on the other hand, has the lowest ionization power among the three, because this capacity it depends almost exclusively on the electrical charge and it has no charge, so it practically does not form ions.
By Jennifer Fogaça
Graduated in Chemistry
Would you like to reference this text in a school or academic work? Look:
FOGAÇA, Jennifer Rocha Vargas. "Ionizing Power of Natural Radioactive Emissions"; Brazil School. Available in: https://brasilescola.uol.com.br/quimica/poder-ionizacao-das-emissoes-radioativas-naturais.htm. Accessed on June 27, 2021.
