Ionizing radiation

Ionizing radiation is a form of radiation that carries enough energy to ionize atoms, knocking electrons closest to atomic nuclei.

Ionizing radiation is capable of stripping electrons from atoms and molecules.

What is ionizing radiation?

Ionizing radiation is a form of radiation that carries with it enough energy to rip away electrons that are attached to atoms and molecules. This radiation can be corpuscular in nature, such as alpha and beta radiation, or electromagnetic in nature, such as gamma radiation, X- rays , and some ultraviolet frequencies .

For a form of radiation to ionize atoms and molecules, it must carry a large amount of energy. In the case of electromagnetic waves, only those at the end of the electromagnetic spectrum are capable of ionizing. In the case of corpuscular radiation , it is necessary that the irradiated particles move at very high speeds, equal to or greater than 1% of the speed of light .

According to the FCC , the body responsible for telecommunications and broadcasting in the United States, any electromagnetic radiation that carries energy greater than 10 eV (electron volts), about 1.6 x 10 -18 J, is considered ionizing. This energy is equivalent to that carried by the far ultraviolet , one of the most energetic bands of the ultraviolet, which extends between 122 nm and 200 nm in wavelength.

The classification that indicates the ionization capacity for corpuscular radiation considers the minimum value of 33 eV of energy, approximately 5.28.10 -18 J. Any forms of radiation that present energy levels below 10 eV are considered non-ionizing radiation .

Despite being an ionizing radiation, the X-ray used in imaging exams has low intensity.

Still in relation to ionizing radiation, we can highlight two forms of ionization: direct and indirect. Direct ionization occurs when there is interaction between electrical charges, as in the case of alpha and beta radiation. Indirect ionization, in turn, occurs without interaction between electrical charges , as in ultraviolet radiation, X-rays, gamma rays and in the emission of neutrons, which have no electrical charge.

Effects of ionizing radiation

The effects of ionizing radiation on matter can be divided into nuclear, chemical, electrical and biological:

  • Nuclear Effects : Radiations such as neutron emission, alpha radiation and high energy gamma radiation can induce nuclear transmutations, making atomic nuclei unstable and consequently radioactive.
  • Chemical effects : Among the chemical effects of ionizing radiation, the breaking of chemical bonds that results in the formation of highly reactive free radicals stands out.
  • Electrical effects : The ionization of some compounds exposed to ionizing radiation can cause sudden changes in their conductivity, causing electrical current surges, which can damage sensitive equipment.
  • Biological effects : The biological effects of ionizing radiation are quite diverse. Currently, there are, for example, therapies based on radiation exposure for the treatment of cancer. The biological effects of this type of radiation are divided into two categories: deterministic and stochastic. Deterministic effects are immediate, such as radiation burns or tissue death. On the other hand, stochastic effects are related to the mutation of the genetic code of cells and the emergence of cancer or hereditary diseases.


Radiotherapy is a form of cancer treatment that uses ionizing radiation to fight the growth of cancer cells. Although there are different forms of radiotherapy, they all work in a similar way: ionizing radiation damages cancer cells, preventing the progression of the disease.

Radiation therapy can be used therapeutically to cure, treat, or relieve symptoms caused by some types of cancer . Like any treatment, it can bring with it some unwanted side effects, such as weight and hair loss, feeling tired, etc.

Radiation therapy can be administered to patients externally or internally. In external radiation therapy , a linear particle accelerator produces highly energetic, concentrated beams of X-rays, which are carefully targeted to the site of the malignant tumor. These beams are generally produced by the deceleration of electrons as they collide with a metallic target at speeds close to the speed of light.

There are two modalities of internal radiotherapy: brachytherapy and radioisotope therapy . Brachytherapy consists of the implantation of radiation sources next to the cancerous tumor, minimizing the effect of radiation on healthy tissues. Radioisotope therapy consists of the ingestion of capsules or solutions composed of radioactive elements, such as iodine-131.

External radiation therapy is performed using linear particle accelerators that produce ionizing radiation.

As each type of cancer responds differently to certain radiations, it is sometimes necessary to combine different forms of radiotherapy to achieve the best possible result, minimizing the side effects of the treatment without losing effectiveness.

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