Nuclear Energy Test Review Sheet
Name:__________________________________________________________ period:__________
1. What does “radioactive” mean?
Radioactive materials have unstable nuclei, which go through changes by emitting
particles and/or releasing energy to become stable
2. What can be expected from a “radioactive nucleus?”
They will “decay” by emitting alpha, beta, gamma or neutron radiation.
3. What is Nuclear Fission?The process by which a nucleus splits into two or more smaller atoms and releases
neutrons and energy
a. How do we get energy from this?
Nuclear power plants and atomic bombs harness the energy emitted when the
nucleus splits.
b. What does E=mc2 stand for?
This is the equation that relates how matter can be converted to energy using
nuclear fission.
c. Draw a picture of it:
d. What are some advantages and disadvantages?
Advantages: no air pollution, small amount of matter gives us a LOT of energy
Disadvantages: Radioactive waste cannot be made safe and must be stored.
Will only become safe after MANY half lives (thousands of years), Possibility of a
plant meltdown releasing dangerous radiation into the air, water, etc.
e. What is Critical Mass? What is a chain reaction?
Critical Mass: the minimum amount of a
substance that can undergo a fission
reaction and can also sustain a chain
reaction.
A chain reaction occurs when the products
of one reaction (nuclear fission) cause the
next to divide. Creating an ongoing
reaction that releases energy.
4. What is an isotope?
Two or more atoms with the same atomic number but different mass numbers (same #
of protons, but different # of neutrons)
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5. Write the nuclear notation for the following isotopes: Chlorine 35 and Chlorine 37.
Describe the differences and similarities between the two isotopes.
35
and
Cl
17
37
Cl
17
Both isotopes have the same number of
protons (17) but they have different
numbers of neutrons (therefore the 35 vs
37 mass numbers)
6. What is nuclear fusion?
The process of smaller nuclei fusing together at high temperatures and releasing
energy
b. Draw a picture of it.
+
+
c. What produces more energy/gram of fuel: fission or fusion? fusion
d. Why can’t we make this happen on Earth?
Has to occur at VERY high temperatures (like the core of the sun)
7. What is background radiation?
Radiation all around us- mostly from natural sources like radon and leftover cosmic
rays from the big bang.
a. Where does it come from?
Virtually everywhere! Plants absorb it from the ground, our air has trace
amounts, etc.
8. List the energy transformations that occur in a nuclear powerplant.
Nuclear Energy Thermal Energy (heat)  Mechanical Energy  Electrical Energy
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9. Fill in the chart below to compare the types of nuclear radiation/emission:
Alpha Particle
What
(exactly) is
released?
Symbol?
2 protons and 2
neutrons
An electron (as a
neutron changes
in to a proton)
4
0
2
What stops
it?
How does it
affect the
atom?
Beta
Gamma
Just energy (no
matter)
A piece of
paper
Changes its
identity- subtract
4 from mass and
2 from protons
(atomic #)
Aluminum
Changes its
identity but not
the mass. ADD
one proton to the
atomic #!
A single neutron
1
e
-1
He
Neutron Emission
0
Thin lead or
concrete
nothing
n
Thick lead!!!
Identity stays the
same, but the
mass goes down
by 1.
B. Practice Problems
1. Lead-210 has a half life of 22 years. How long would it take a sample of 354g to decay to
1/16?
 4 half lives have passed ( ½ x ½ x ½ x ½ = 1/16 )
 4 HL x (22 yrs/HL)= 88 years
2. Complete the following nuclear reactions:
a. 23892U  23490Th + 42He
b. 23491Pa 
23089Ac
+ 42He
c. 23491Pa  23492U + 0-1e
d. 10n + 23892U  23590Th+ 42He
e. 22086Rn  22086Rn +
00γ
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Use the chart to answer questions below:
Radioactive
Substance
Radon-222
Iodine-131
Radium-226
Carbon-14
Plutonium-239
Uranium-238
Approximate HalfLife
4 days
8 days
1,600 years
5,730 years
24,120 years
4,470,000,000 years
3. If we start with 8000 atoms of radium- 226, how much would remain after 3,200 years?
2,000 atoms
1HL= 1,600 years
32,000 years= 2 Half lives
2HL= ½ x ½ = ¼ remains
¼ of 8000= 2000 atoms
5. If we start with 60 atoms of uranium-238, how many remain after 4,470,000,000 years?
1 HL has passed so ½ of 60 = 30 atoms
6. If we start with 24 atoms of iodine-131, how many remain after 32 days?
1 HL= 8 days so after 32 days, 4 half lives have passed.
( ½ x ½ x ½ x ½ = 1/16 )
1/16 of 24 atoms is 1.5 atoms
7. You find a sample of Uranium that is in the process of decaying. If there were 3,000
grams initially and there are only 187.5 grams still radioactive (parent atoms), how many half
lives have passed?
187.5 grams divided by 3,000 grams is .0625 or 1/16th
This means that 4 half lives have passed.
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