Question 1

Which of the following statements about fusion is the most accurate?

Accepted Answer

A) The mass of the products is less than the mass of the reactants. 
B) The mass of the reactants is less than the mass of the products. 
C) A nuclear fusion will always release energy. 
D) Overcoming the strong nuclear force results in the release of a large amount of energy. 
E) Fission releases more energy than fusion.

Question 2

Just after an alpha particle leaves the nucleus, would you expect it to speed up? Why?

Accepted Answer

A) No. Once the alpha particle leaves the nucleus it is slowed by the repulsion of the next closest atom's nucleus. 
B) No. As the alpha particle leaves the nucleus it is slowed by the constant attraction of the electrons surrounding the nucleus. 
C) Yes. Once the alpha particle leaves the nucleus there are no more forces acting on it and it therefore accelerates. 
D) Yes. Once the alpha particle leaves the nucleus it accelerates because of mutual electric repulsion with the nucleus from which it escaped.

Question 3

What is transmutation?

Accepted Answer

A) changing one element into another by adding or removing protons from the nucleus 
B) changing one element into another by adding or removing electrons from the nucleus 
C) changing one element into another by adding or removing neutrons from the nucleus 
D) a process that emits radiation 
E) alteration in DNA due to radioactivity

Question 4

Which of the following statements best describes the role of neutrons in the nucleus?

Accepted Answer

A) The neutrons stabilize the nucleus by attracting other nucleons. 
B) The neutrons stabilize the nucleus by forming bonds with other neutrons. 
C) The neutrons stabilize the nucleus by attracting protons. 
D) The neutrons stabilize the nucleus by balancing charge. 
E) The neutrons stabilize the nucleus by adding mass.

Question 5

Which of the following nuclear equations correctly describes alpha emission?

Accepted Answer

A)   Th →  Pa +  e 
B)   Th →  Ac +  e 
C)   Th →  Pa +  e 
D)   Th →  e 
E) none of the above

Question 6

When  Ra decays by emitting an alpha particle, what is the atomic number of the resulting nucleus? What is the resulting atomic mass?

Accepted Answer

A) atomic number = 86; atomic mass = 222 
B) atomic number = 87; atomic mass = 226 
C) atomic number = 86; atomic mass = 224 
D) atomic number = 87; atomic mass = 224

Question 7

Where did the atoms that make up a newborn baby originate?

Accepted Answer

A) in the womb of the baby's mother 
B) in the digestion of the food that the mother ate 
C) in the earth through geological processes 
D) in the explosions of ancient stars

Question 8

A pair of protons in an atomic nucleus repel each other, but they are also attracted to each other. Why?

Accepted Answer

A) The pair repel each other by nuclear force but attract one another by an electrical force. 
B) The pair repel each other since they are both positively charges but they are held together by much stronger forces known as quarks. 
C) The pair attract each other by nuclear force but also repel one another by a weaker electrical force. 
D) Although it is known that protons repel each other at short distances because of like charge, it is not known what actually holds protons together in the nucleus because we have never seen the nucleus of an atom.

Question 9

Complete the following nuclear equation:  Tl →  Pb + ??

Accepted Answer

A)   e 
B)   He 
C) gamma ray 
D) both A and B 
E) none of the above

Question 10

Uranium-235 releases an average of 2.5 neutrons per fission, while plutonium-239 releases an average of 2.7 neutrons per fission. Which of these elements might you therefore expect to have the smaller critical mass?

Accepted Answer

A) plutonium-239 
B) uranium-235 
C) The number of neutrons per fission will not affect the size of critical mass. 
D) The critical mass of these elements cannot be determined from only the number of neutrons per fission.

Question 11

Why does plutonium not occur in appreciable amounts in natural ore deposits?

Accepted Answer

A) Most naturally occurring plutonium deposits have already been depleted in the creation of nuclear weapons. 
B) Plutonium is strictly a human-made element. 
C) Any plutonium initially in the earth's crust has long since decayed. 
D) Plutonium loses electrons to form positively charged particles that have long since washed into the oceans.

Question 12

Why might the following nuclear reaction not be very good for energy production in a fusion reactor?  Fe +  Fe →  Te

Accepted Answer

A) The material only produces a few neutrons so the chain reaction will not be very efficient. 
B) The reactants are too stable and it would cost energy to produce the product due to strong nuclear force. 
C) The products are not the right size to obtain any energy from the missing mass due to the strong nuclear force. 
D) The mass of the byproducts is too high and therefore the energy released will not be high enough. 
E) Interatomic attraction between the products will impede the separation of the atoms from the unstable nuclei.

Question 13

How many alpha particles are emitted in the series of radioactive decay events from a U-238 nucleus to a Pb-206 nucleus?

Accepted Answer

A) 32 
B) 16 
C) 8 
D) 4

Question 14

In bombarding atomic nuclei with proton "bullets," the protons must be accelerated to high energies to make contact with the target nuclei

Accepted Answer

A) because the target nuclei are so small. 
B) because the target nuclei are negatively charged. 
C) in order to penetrate through the electrons that surround each target nucleus. 
D) because the target nuclei are positively charged.

Question 15

The original reactor built in 1942 was just "barely" critical because the natural uranium that was used contained less than 1% of the fissionable isotope U-235 (half-life 713 million years). What if, in 1942, the Earth had been 9 billion years old instead of 4.5 billion years old? Would this reactor have reached critical stage with natural uranium? Why?

Accepted Answer

A) No. The age of the Earth has nothing to do with the reactor reaching critical stage with U-235. 
B) No. 1% of the fissionable isotope U-235 is insufficient for the reactor to reach critical stage no matter what the age of the Earth. 
C) Yes. If the Earth had been twice as old there would have then been twice as much fissionable U-235 present and the reactor would have reached critical stage. 
D) No. The increased age of the Earth would mean that there would be a much smaller percentage of U-235, thus not enough for the reactor to reach critical stage.

Question 16

When  Po emits a beta particle, it transforms into a new element. What are the atomic number and atomic mass of this new element?

Accepted Answer

A) atomic number = 84; atomic mass = 219 
B) atomic number = 86; atomic mass = 214 
C) atomic number = 85; atomic mass = 218 
D) atomic number = 82; atomic mass = 214

Question 17

Which of the following statements about fusion is true?

Accepted Answer

A) Fusion reactions have no critical-mass requirement. 
B) Fusion is easier than fission. 
C) Fusion reactions can be easily controlled to make energy. 
D) Fusion produces no harmful radiation. 
E) none of the above

Question 18

Which of the beams is due to alpha particles?

Accepted Answer

A) a 
B) b 
C) c 
D) all of the above 
E) none of the above

Question 19

If a nucleus of  Th absorbs a neutron and the resulting nucleus undergoes two successive beta decays (emitting electrons), what nucleus results?

Accepted Answer

A) americium-232 
B) plutonium-232 
C) thorium-233 
D) uranium-233

Question 20

What is a half-life?

Accepted Answer

A) It is the time it takes for 1/2 of the material to undergo radiodecay. 
B) It is the time needed until 1/2 of the radiation is gone. 
C) It is the time it takes for 1/2 of the material to decompose. 
D) It is half of the lifetime of the radioactivity in a sample. 
E) all of the above

Exam 10: The Atomic Nucleus and Radioactivity