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1 . Differentiate among alpha and
beta particles and gamma radiation .
2 . Differentiate between fission and
fusion .
3 . Explain the process half-life as
related to radioactive decay .
4. Describe nuclear energy , its
practical application as an alternative
energy source , and its potential
problems.

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Radioactivity is the spontaneous
disintegration of atomic nuclei. The
nucleus emits α particles, ß
particles, or electromagnetic rays
during this process.
After decaying, radioactive atoms
“change” into other atoms

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• Why does the atom do this?
– the nucleus of an atom attempts to become
more stable
• In some instances, a new element is
formed and in other cases, a new form
of the original element, called an
isotope, appears.
– this process of change is often referred to as
the decay of atoms.
• The rate of Radioactive decay is
described in half-lives.

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Energy is released during
radioactive decay

TED ed: Radioactivity: Expect the Unexpected

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Types of Nuclear
Radiation
• When an unstable
nucleus decays,
particles and energy
are given off from the
decaying nucleus.
• α and β radiation is in
the form of particles
• γ radiation is in the
form of waves-kind of
like light but higher
frequency

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Nuclear Decay
2 protons & 2 neutrons
Neutron decays into a proton
& an electron is given off
Only Energy is release

• 8 Alpha particles consist of two protons and two
neutrons, identical to the nucleus of a helium
atom.
• A sheet of paper or a person’s surface layer of
skin will stop them.
• Alpha particles are only considered hazardous to
a person’s health if they are ingested or inhaled
and thus come into contact with sensitive cells
such as in the lungs, liver and bones.

Examples of Alpha Decay

• Beta particles are electrons emitted from the nuclei
of many fission products.
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•They can travel a few
feet in air but can usually
be stopped by clothing or
a few centimeters of
wood.
•They are considered
hazardous mainly if
ingested or inhaled, but
can cause radiation
damage to the skin if the
exposure is large enough.
•Unstable Neutron decays
into a proton.

Examples of Beta Decay
Beta Decay
with
Gamma
Radiation

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• Gamma rays are a form of electromagnetic
radiation (like light, radio, and television) that
come from the nucleus of a radioactive atom.
– Occurs when an unstable nucleus emits electromagnetic
radiation. The radiation has no mass, and so its emission
does not change the element.
– They penetrate matter easily and are best stopped by
water or thick layers of lead or concrete.
– Gamma radiation is hazardous to people inside and outside
of the body.
•However, gamma radiation often accompanies alpha and
beta emission, which do change the element's identity.
•Gamma rays have the lowest ionizing power, but the highest
penetrating power.
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Gamma Radiation

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Biological Effects of Radiation:
Ionizing radiation causes physical
damage to cells and DNA.
Radiation can excite DNA and result
in the destruction on the DNA
backbone.
At high doses of radiation (10,000 -
15,000 rads), death occurs in a few
hours because of neurological and
cardiovascular breakdown (Central
Nervous Syndrome).

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Biological Effects of Radiation:
Medium doses, 500 - 1200 rads,
causes death to occur in a few days
because of the destruction of the
gastrointestinal mucosa.
Lower doses, 250 - 500 rads,
causes death to occur after several
weeks due to damage of the blood
forming organs (hematopoietic
syndrome).

Radiation is used positively in a variety of ways 15
Medicine
•For example, radiation and radioactive
tracers are used to diagnose and treat medical
problems.
•A radioactive tracer is a radioactive isotope
that is added to a substance so that the
substance can be detected later.
•Radioactive tracers are used to locate tumors, to
study the functioning of a particular organ, or to
monitor the flow of blood.
•For example, radioactive iodine-131 is used
to diagnose thyroid problems.
•Radiation therapy used to treat cancer may
involve the use of implanted radioactive isotopes such as
gold-198 or iridium-192.

Industry
•Manufacturers can also use radiation to
check the thickness of metal
containers by measuring the amount of
radiation that passes through.
•Small amounts of radioactive isotopes,
like magnesium-28, can be introduced in a
water source to determine the flow of
underground water or to determine if an
underground water system is leaking.
•Radioactive isotopes are even used in
smoke alarms.
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Generate electrical power
Nuclear fission is used to generate
electricity as an alternative energy
source.
Dating- finding the age
Even the age of fossils or rocks can
be determined by using radioactive
isotopes.

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Fission and Fusion
Fission
Fusion
Splitting a nucleus
Combining of two nuclei.

•Nuclear power can
come from the fission
of uranium, plutonium
or thorium or the fusion
of hydrogen into
helium.
•Today it is almost all
uranium.
•The fission of an atom
of uranium produces 10
million times the energy
produced by the
combustion of an atom
of carbon from coal.
•Chain Reaction video
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Issues for Fission Power Plants
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•Need for a spent fuel disposal facility
and a decommissioning plan
•Use of large amounts of water for
cooling purposes (if wet cooling towers
are used) –thermal pollution
•Biological impacts on the ocean due to
thermal discharge (if seawater cooling is
used)
•Public safety concerns
Bill Nye Clip

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FUSION
•Fusion reaction: occurs when nuclei of light elements
are forced together at extremely high temperatures
until they fuse into nuclei of heavier elements and
release enormous amounts of energy.
•Issues: The fuel must be heated in the form of
plasma (a highly ionized gas) to a very high
temperature.

Identify each type of reaction…alpha, beta, gamma, fusion or
fission...write your answers below your crossword on the ½ sheet.
1.
2.
3.
4.
5.

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Half Life is the amount of time it takes
for half of the nuclei in a sample to decay
Bill Nye Explains Half Life
Mass
(kg)

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C
14
C
mass number
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C
• Carbon occurs naturally in three
isotopes.
• All of these atoms have the same
number of protons but different
numbers of neutrons.
• The number of neutrons and protons
determines the mass, so the masses
are different.
• 14 C is radioactive.

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C
• Radioactive 14 C acts chemically just like
12
C, so it becomes incorporated into plants
an animals.
• When the animal/plant dies the 14 C begins
to decay into 14 N at a know rate, so we
can determine how long ago the organism
died.
• This is called Carbon Dating.
• It’s only good for about 50,000 years.

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• The half life of 14 C is 5,730 years.
• If a sample originally contained
100 g, how much would be left
after 11,460 years?
50g
25g

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Older Dating Methods
• The isotopes 235 U and 238 U
can be used to date
objects billions of years
old.
• 235 U has a half life of 704
million years.
• 238 U has a half life of 4.5
billion years.
• Mainly used for rocks.

Geiger Counter
• Used to
measure
radiation.
• The more
intense the
radiation the
more “clicks”.