Section what is radioactivity

Neutron emission is the ejection of a neutron from the nucleus. It can happen spontaneously, like the decay of beryllium to beryllium, or in response to bombardment by gamma rays or particles.

The atomic number remains unchanged during this process, whereas the mass number decreases by one. The conversion of potassium to argon exemplifies the emission of energy due to electron capture. The potassium nucleus captures an inner electron in the atom, and a proton converts to a neutron. An outer electron drops to the inner level to fill the vacancy, characterized by an emission of X-rays with an energy corresponding to the transition.

The penetration power of alpha particles, which are the most massive of the nuclear particles, is very low, whereas gamma radiation passes through most materials. Neutrons and beta particles can be blocked effectively by relatively lightweight materials. The electron emitted is from the atomic nucleus and is not one of the electrons surrounding the nucleus. Emission of an electron does not change the mass number of the nuclide but does increase the number of its protons and decrease the number of its neutrons.

An antineutrino is also emitted owing to conservation of energy. Positron decay is the conversion of a proton into a neutron with the emission of a positron. The atomic number remains unchanged during this process, whereas the mass number decreases by 1.

For example, potassium undergoes electron capture:. Electron capture occurs when an inner-shell electron combines with a proton and is converted into a neutron. The loss of an inner-shell electron leaves a vacancy that will be filled by one of the outer electrons. As the outer electron drops into the vacancy, it will emit energy. In most cases, the energy emitted will be in the form of an X-ray.

Electron capture has the same effect on the nucleus as positron emission does: the atomic number is decreased by one and the mass number does not change.

This text is adapted from Openstax, Chemistry 2e, Section To learn more about our GDPR policies click here. If you want more info regarding data storage, please contact gdpr jove. Your access has now expired. Provide feedback to your librarian. If you have any questions, please do not hesitate to reach out to our customer success team. Login processing Chapter Radioactivity and Nuclear Chemistry. Chapter 1: Introduction: Matter and Measurement. Chapter 2: Atoms and Elements.

Chapter 3: Molecules, Compounds, and Chemical Equations. Chapter 4: Chemical Quantities and Aqueous Reactions. Chapter 5: Gases. Chapter 6: Thermochemistry. Chapter 7: Electronic Structure of Atoms. Collection of the radiation offers further confirmation from the direct measurement of excess charge.

Evidence for this grew, but it was not until that this was proved by Rutherford and collaborators. All three types of nuclear radiation produce ionization in materials, but they penetrate different distances in materials—that is, they have different ranges.

Let us examine why they have these characteristics and what are some of the consequences. Figure 3. These dosimeters literally, dose meters are personal radiation monitors that detect the amount of radiation by the discharge of a rechargeable internal capacitor. The amount of discharge is related to the amount of ionizing radiation encountered, a measurement of dose. One dosimeter is shown in the charger.

Its scale is read through an eyepiece on the top. Chang, Wikimedia Commons. The energy emitted in various nuclear decays ranges from a few keV to more than 10 MeV, while only a few eV are needed to produce ionization. The effects of x rays and nuclear radiation on biological tissues and other materials, such as solid state electronics, are directly related to the ionization they produce. All of them, for example, can damage electronics or kill cancer cells. In addition, methods for detecting x rays and nuclear radiation are based on ionization, directly or indirectly.

All of them can ionize the air between the plates of a capacitor, for example, causing it to discharge. This is the basis of inexpensive personal radiation monitors, such as pictured in Figure 3. We define ionizing radiation as any form of radiation that produces ionization whether nuclear in origin or not, since the effects and detection of the radiation are related to ionization.

The range of radiation is defined to be the distance it can travel through a material. Range is related to several factors, including the energy of the radiation, the material encountered, and the type of radiation see Figure 4.

The higher the energy , the greater the range, all other factors being the same. This makes good sense, since radiation loses its energy in materials primarily by producing ionization in them, and each ionization of an atom or a molecule requires energy that is removed from the radiation.

The amount of ionization is, thus, directly proportional to the energy of the particle of radiation, as is its range. Figure 4. The penetration or range of radiation depends on its energy, the material it encounters, and the type of radiation. Radiation can be absorbed or shielded by materials, such as the lead aprons dentists drape on us when taking x rays. Lead is a particularly effective shield compared with other materials, such as plastic or air.

How does the range of radiation depend on material? Ionizing radiation interacts best with charged particles in a material. Since electrons have small masses, they most readily absorb the energy of the radiation in collisions. The greater the density of a material and, in particular, the greater the density of electrons within a material, the smaller the range of radiation. Conservation of energy and momentum often results in energy transfer to a less massive object in a collision.

This was discussed in detail in Work, Energy, and Energy Resources, for example. Different types of radiation have different ranges when compared at the same energy and in the same material. Alphas have the shortest range, betas penetrate farther, and gammas have the greatest range. This is directly related to charge and speed of the particle or type of radiation. The more readily the particle produces ionization, the more quickly it will lose its energy.

The smaller the charge, the smaller is F and the smaller is the momentum and energy lost. Step 2. Use the Isotope Remaining equation to solve for how much isotope will remain after the number of half-lives determined in step 1 have passed. Damaging Effects of Ionizing Radiation. Lower frequency, lower-energy electromagnetic radiation is nonionizing, and higher frequency, higher-energy electromagnetic radiation is ionizing.

Energy absorbed from nonionizing radiation speeds up the movement of atoms and molecules, which is equivalent to heating the sample.

Although biological systems are sensitive to heat as we might know from touching a hot stove or spending a day at the beach in the sun , a large amount of nonionizing radiation is necessary before dangerous levels are reached. Ionizing radiation, however, may cause much more severe damage by breaking bonds or removing electrons in biological molecules, disrupting their structure and function Figure 3.

Biological Effects of Ionizing Radiation. Ionizing radiation can directly damage a biomolecule by ionizing it or breaking its bonds. Radiation can harm either the whole body somatic damage or eggs and sperm genetic damage. Its effects are more pronounced in cells that reproduce rapidly, such as the stomach lining, hair follicles, bone marrow, and embryos.

This is why patients undergoing radiation therapy often feel nauseous or sick to their stomach, lose hair, have bone aches, and so on, and why particular care must be taken when undergoing radiation therapy during pregnancy. Radioactive isotopes have the same chemical properties as stable isotopes of the same element, but they emit radiation, which can be detected.

If we replace one or more atom s with radioisotope s in a compound, we can track them by monitoring their radioactive emissions. This type of compound is called a radioactive tracer or radioactive label.

Radioisotopes are used to follow the paths of biochemical reactions or to determine how a substance is distributed within an organism. Radioactive tracers are also used in many medical applications, including both diagnosis and treatment.

They are also used in many other industries to measure engine wear, analyze the geological formation around oil wells, and much more. Radioisotopes have revolutionized medical practice , where they are used extensively. Over 10 million nuclear medicine procedures and more than million nuclear medicine tests are performed annually in the United States. Four typical examples of radioactive tracers used in medicine are technetium , thallium , iodine , and sodium Damaged tissues in the heart, liver, and lungs absorb certain compounds of technetium preferentially.

Thallium Figure 3. Iodine concentrates in the thyroid gland, the liver, and some parts of the brain. Salt solutions containing compounds of sodium are injected into the bloodstream to help locate obstructions to the flow of blood.

Administering thallium to a patient and subsequently performing a stress test offer medical professionals an opportunity to visually analyze heart function and blood flow.

Radioisotopes used in medicine typically have short half-lives—for example, Tc has a half-life of 6. This makes Tc essentially impossible to store and prohibitively expensive to transport, so it is made on-site instead.

Hospitals and other medical facilities use Mo which is primarily extracted from U fission products to generate Tc The parent nuclide Mo is part of a molybdate ion, ; when it decays, it forms the pertechnetate ion,. These two water-soluble ions are separated by column chromatography, with the higher charge molybdate ion adsorbing onto the alumina in the column, and the lower charge pertechnetate ion passing through the column in the solution.

A few micrograms of Mo can produce enough Tc to perform as many as 10, tests. The MoO 4 2- is retained by the matrix in the column, whereas the TcO 4 —.

The scan shows the location of high concentrations of Tc To perform a PET scan, a positron-emitting radioisotope is produced in a cyclotron and then attached to a substance that is used by the part of the body being investigated. For example, F is produced by proton bombardment of 18 O and incorporated into a glucose analog called fludeoxyglucose FDG.

How FDG is used by the body provides critical diagnostic information; for example, since cancers use glucose differently than normal tissues, FDG can reveal cancers.

The 18 F emits positrons that interact with nearby electrons, producing a burst of gamma radiation. Different levels of gamma radiation produce different amounts of brightness and colors in the image, which can then be interpreted by a radiologist to reveal what is going on.

Unlike magnetic resonance imaging and X-rays, which only show how something looks, the big advantage of PET scans is that they show how something functions. PET scans are now usually performed in conjunction with a computed tomography scan.

Radioisotopes can also be used, typically in higher doses than as a tracer, as treatment. Radiation therapy is the use of high-energy radiation to damage the DNA of cancer cells, which kills them or keeps them from dividing Figure 3. A cancer patient may receive external beam radiation therapy delivered by a machine outside the body, or internal radiation therapy brachytherapy from a radioactive substance that has been introduced into the body. Note that chemotherapy is similar to internal radiation therapy in that the cancer treatment is injected into the body, but differs in that chemotherapy uses chemical rather than radioactive substances to kill the cancer cells.

The cartoon in a shows a cobalt machine used in the treatment of cancer. The diagram in b shows how the gantry of the Co machine swings through an arc, focusing radiation on the targeted region tumor and minimizing the amount of radiation that passes through nearby regions. The overall process is:. The overall decay scheme for this is shown graphically in Figure 3. Co undergoes a series of radioactive decays. Radioisotopes are used in diverse ways to study the mechanisms of chemical reactions in plants and animals.

These include labeling fertilizers in studies of nutrient uptake by plants and crop growth, investigations of digestive and milk-producing processes in cows, and studies on the growth and metabolism of animals and plants.

For example, the radioisotope C was used to elucidate the details of how photosynthesis occurs. The overall reaction is:. In studies of the pathway of this reaction, plants were exposed to CO 2 containing a high concentration of. At regular intervals, the plants were analyzed to determine which organic compounds contained carbon and how much of each compound was present.

From the time sequence in which the compounds appeared and the amount of each present at given time intervals, scientists learned more about the pathway of the reaction.