ChemCh25.4.ppt

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25.4 Radiation in Your Life >

Chapter 25

Nuclear Chemistry

25.1 Nuclear Radiation

25.2 Nuclear Transformations 25.3 Fission and Fusion

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How does a smoke

detector work?

CHEMISTRY & YOU

CHEMISTRY & YOU

A typical household smoke detector

contains a small amount of americium, Am, in the form of AmO₂.

Americium-241 is a radioisotope.

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25.4 Radiation in Your Life > Detecting RadiationDetecting Radiation

Detecting Radiation

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Radiation emitted by radioisotopes has

enough energy to knock electrons off

some atoms of a bombarded substance,

producing ions.

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It is not possible for humans to see, hear,

smell, or feel ionizing radiation.

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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.

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Radiation can expose a photographic plate.

• When the plate is developed, its

darkened areas show where the plate has been exposed to

radiation.

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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?

CHEMISTRY & YOU

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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?

CHEMISTRY & YOU

CHEMISTRY & YOU

Once the ions in the air inside the smoke

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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.

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Geiger Counter

Geiger 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.

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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.

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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.

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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

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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.

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Which of the following detectors would

you use to locate uranium ores in a soil

sample?

A. Geiger counter

B. scintillation counter

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Which of the following detectors would

you use to locate uranium ores in a soil

sample?

A. Geiger counter

B. scintillation counter

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25.4 Radiation in Your Life > Using RadiationUsing Radiation

Using Radiation

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Using Radiation

What are some practical uses of

radioisotopes?

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Scientists use radiation to detect trace

amounts of elements in samples.

• This process is called neutron activation analysis.

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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

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Analyzing Matter

• Museums use this process to detect art

forgeries.

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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.

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The tracer may also be monitored in

animals that consume the plants, as well as

in water and soil.

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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.

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• The radioisotope technetium-99m is

used to detect brain tumors and liver

disorders.

• Phosphorus-32 is used to detect skin

cancer.

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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.

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Fast-growing cancer cells are more

susceptible to damage by high-energy

radiation such as gamma rays than are

healthy cells.

Treating Diseases

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Some normal cells are also killed, however,

and cancer cells at the center of the tumor

may be resistant to the radiation.

Treating Diseases

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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.

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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.

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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

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Describe the benefits and risks of

radiation therapy for cancer.

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25.4 Radiation in Your Life > Key ConceptsKey Concepts

Geiger counters, scintillation

counters, and film badges are

commonly used to detect radiation.

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25.4 Radiation in Your Life > Glossary TermsGlossary Terms

ionizing radiation: radiation with enough

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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 IDEA

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