25.4 radiation in your life > 1 copyright © pearson education, inc., or its affiliates. all...

25.4 Radiation in Your Life >25.4 Radiation in Your Life >

1 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Chapter 25Nuclear Chemistry

25.1 Nuclear Radiation25.2 Nuclear Transformations25.3 Fission and Fusion

25.4 Radiation in Your Life



How does a smoke detector work?

CHEMISTRY & YOUCHEMISTRY & YOU

A typical household smoke detector contains a small amount of americium, Am, in the form of AmO2. Americium-241 is a radioisotope.

24195



Detecting RadiationDetecting Radiation

Detecting Radiation

What are three devices used to detect radiation?




Radiation emitted by radioisotopes has enough energy to knock electrons off some atoms of a bombarded substance, producing ions.• The radiation emitted by radioisotopes is

called ionizing radiation.




It is not possible for humans to see, hear, smell, or feel ionizing radiation.

• People must rely on detection devices to alert them to the presence of radiation and to monitor its level.




It is not possible for humans to see, hear, smell, or feel ionizing radiation.

• People must rely on detection devices to alert them to the presence of radiation and to monitor its level.

• These devices work because of the effects of the radiation when it strikes atoms or molecules in the detector.




Radiation can expose a photographic plate.

• When the plate is developed, its darkened areas show where the plate has been exposed to radiation.

• X-rays allow doctors to see inside the body without having to cut into the body. Color was added to highlight parts of the image.



Radiation emitted in a smoke detector ionizes the nitrogen and oxygen in the air, and a current flows. When smoke particles attach to the ions, the ions lose their charge. What happens next?




Radiation emitted in a smoke detector ionizes the nitrogen and oxygen in the air, and a current flows. When smoke particles attach to the ions, the ions lose their charge. What happens next?


Once the ions in the air inside the smoke detector lose their charge, the current decreases. An electronic circuit detects the drop in current, which causes an alarm to sound.




Geiger counters, scintillation counters, and film badges are commonly used to detect radiation.




Geiger Counter

A Geiger counter uses a gas-filled metal tube to detect radiation.

• When ionizing radiation penetrates a thin window at the end of the tube, the gas inside the tube becomes ionized.

• Each time a Geiger tube is exposed to radiation, current flows.

• The bursts of current drive electronic counters or cause audible clicks from a built-in speaker.




Geiger CounterGeiger counters can detect alpha, beta, and gamma radiation.• Astronomers use Geiger counters

to detect cosmic rays from outer space.

• Geologists use Geiger counters to search for radioactive minerals.

• This person is using a Geiger counter to check for radiation in contaminated dirt at a spill site.




Scintillation Counter

A scintillation counter uses a phosphor-coated surface to detect radiation.

• When ionizing radiation strikes the surface, the phosphor produces bright flashes of light, or scintillations.

• The number of flashes and energies are detected electronically.




Scintillation Counter

Scintillation counters are more sensitive than Geiger counters.

• They can detect some radiation that would not be detected by a Geiger counter.

• Scintillation counters are used to track the path of radioisotopes through the body.

• They are also used to monitor the possible transport of radioactive materials across national borders and through airports.




Film Badge

This is a diagram of a typical film badge.

• The badge contains layers of photographic film covered with black light-proof paper.

• To reach the film, radiation must pass through a filter, which absorbs some radiation, or a transparent area through which radiation can pass easily.




Film Badge

People who work with or near ionizing radiation must wear a film badge to monitor their exposure while they are at work.

• At specific intervals, the film is removed and developed.

• The strength and type of radiation exposure are determined by comparing the darkness of the film in all the exposed areas.



Which of the following detectors would you use to locate uranium ores in a soil sample?

A. Geiger counter

B. scintillation counter

C. film badge



Using RadiationUsing Radiation

Using Radiation

What are some practical uses of radioisotopes?




Using Radiation

What are some practical uses of radioisotopes?

• Although radiation can be harmful, it can be used safely and has many important applications.




Radioisotopes are used to analyze matter, study plant growth, diagnose medical problems, and treat diseases.




Scientists use radiation to detect trace amounts of elements in samples.

• This process is called neutron activation analysis.

Analyzing Matter




Analyzing Matter• A sample is bombarded with neutrons from a

radioactive source.

• Some atoms in the sample become radioactive.

• The half-life and type of radiation emitted can be detected and analyzed by a computer.– Because this data is unique for each isotope,

scientists can determine what radioisotopes were produced and infer what elements were in the original sample.




Analyzing Matter

• Museums use this process to detect art forgeries.

• Crime laboratories use it to analyze gunpowder residue.




Radioisotopes called tracers are used in agriculture to test the effects of herbicides, pesticides, and fertilizers on plants.• A tracer is introduced into the substance being

tested.

• Next, plants are treated with the tagged substance.

• Devices that detect radioactivity are used to locate the substance in the plants.

Using Tracers




The tracer may also be monitored in animals that consume the plants, as well as in water and soil.

Using Tracers




Radioisotopes can be used to detect disorders of the thyroid gland, which is located in the throat.

• To diagnose thyroid disease, the patient is given a drink containing a small amount of the radioisotope iodine-131.

• After about two hours, the amount of iodide uptake is measured by scanning the patient’s throat with a radiation detector.

Diagnosing Medical Problems




• The radioisotope technetium-99m is used to detect brain tumors and liver disorders.

• Phosphorus-32 is used to detect skin cancer.

Diagnosing Medical Problems




Radiation is one method used in the treatment of some cancers.

Treating Diseases

• Cancer is a disease in which abnormal cells in the body are produced at a rate far beyond the rate for normal cells.

• The mass of cancer cells that result from this runaway growth is called a tumor.




Fast-growing cancer cells are more susceptible to damage by high-energy radiation such as gamma rays than are healthy cells.

Treating Diseases

• Radiation can be used to kill the cancer cells in a tumor.




Some normal cells are also killed, however, and cancer cells at the center of the tumor may be resistant to the radiation.

Treating Diseases

• The benefits of the treatment and the risks to the patient must be carefully evaluated before radiation treatment begins.




Some normal cells are also killed, however, and cancer cells at the center of the tumor may be resistant to the radiation.

Treating Diseases

• The benefits of the treatment and the risks to the patient must be carefully evaluated before radiation treatment begins.

• Cobalt-60 and cesium-137 are typical radiation sources for cancer therapy.




Salts of radioisotopes can also be sealed in gold tubes and directly inserted in tumors.

Treating Diseases

• This method of treatment is called seeding.

• The salts emit beta and gamma rays that kill the surrounding cancer cells.

• Because the radioisotope is in a sealed container, it is prevented from traveling to other parts of the body.




Prescribed drugs containing radioisotopes of gold, iodine, or phosphorus are sometimes used in radiation therapy.

Treating Diseases

• A dose of iodine-131 larger than that used to detect thyroid diseases can be given to a patient to treat the disease.

• The iodine that collects in the gland emits beta particles and gamma rays, which provide therapy.



Describe the benefits and risks of radiation therapy for cancer.



Describe the benefits and risks of radiation therapy for cancer.

Radiation therapy can kill cancer cells at a higher rate than healthy cells, so it can be used to destroy fast-growing tumors. However, it also damages healthy cells, and cells in the center of the tumor may not be reached by the radiation.



Key ConceptsKey Concepts

Geiger counters, scintillation counters, and film badges are commonly used to detect radiation.

Radioisotopes are used to analyze the composition of matter, study plant growth, diagnose medical problems, and treat diseases.



Glossary TermsGlossary Terms

ionizing radiation: radiation with enough energy to knock electrons off some atoms of a bombarded substance to produce ions



Electrons and the Structure of Atoms

• The ability to detect particles emitted when nuclei decay helps scientists study processes that take place in living organisms.

• This ability also allows scientists to determine the age of fossils and other objects.

BIG IDEABIG IDEA



END OF 25.4END OF 25.4

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