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1 1. The gravitational force is the fundamental force that exists between A) any objects that have mass. C) the protons and neutrons in an atomic nucleus. B) any objects that have charge. D) is not a fundamental force at all. 2. The electrostatic force is the fundamental force that exists between A) any objects that have mass. C) the protons and neutrons in an atomic nucleus. B) any objects that have charge. D) is not a fundamental force at all. 3. The strong nuclear force is the fundamental force that exists between A) any objects that have mass. C) the protons and neutrons in an atomic nucleus. B) any objects that have charge. D) is not a fundamental force at all. 4. Compare the behavior of each of these forces with increasing distance. The strength of A) all three forces increases as the distance (between masses, charges, or nuclear particles) increases. B) all three decreases with increasing distance: they are all inverse-square relationships. C) gravity and the electrostatic force decreases with distance, but the nuclear force increases. D) all decreases, but the nuclear force decreases with distance much more rapidly than the other two. 5. Why is the strong nuclear force considered fundamental? A) It isn t. The gravitational and electrostatic forces are sufficient to explain observed nuclear behavior. B) It has properties that it does not share with either the gravitational or electrostatic force. These unique properties are necessary to explain how the neutrons are able to bind protons in the nucleus. C) Because it is stronger than either gravity or the electrostatic force, and the stronger a force is, the more fundamental it is considered to be. D) Because it was discovered before either gravity or the electrostatic force. The earlier something is discovered, the more fundamental it is considered to be. 6. What are the properties of the strong nuclear force? A) It must repel nuclear particles very strongly over large distances. B) It must attract nuclear particles very strongly over very short distances, but outside the nucleus, the strength drops rapidly off to zero. C) It must attract nuclear particles over short distances, but repel them over long distances. D) It must attract protons to neutrons, but repel neutrons from other neutrons. 7. The strong nuclear force acts over distances of about A) m, about the size of an atomic nucleus. B) 10 9 m, about the size of an atomic radius. C) 10 9 m, about the distance from the earth to the sun. D) m, about the distance from the sun to the next nearest star. 8. If the range of the strong force was increased slightly, A) there would be fewer elements on the periodic table because only smaller nuclei could form. B) there would be more elements because larger nuclei would be able to form and be stable. C) there would be no change in the number of possible elements. 9. Why are nuclear energies so large? A) Because the nucleus is so small. The relationship is another example of the inverse-square law. B) According to quantum mechanics and relativity theory, the nuclear particles are so tightly bound in the nucleus that they cannot move. They have zero kinetic energy, but very high potential energy. C) Quantum mechanics and relativity combine to show that if the particle positions are well-defined, their speeds are very large and very uncertain, giving them high energy. D) Protons and neutrons vibrate at very low frequencies. The lower the frequency of vibration, the higher the energy of the particle. 10. The structure of an atomic nucleus A) can be changed in a nuclear reaction. B) is fixed and unchanging, maintaining a steady state for the life of the atom. C) is unknown, because it is not possible to see the particles that make up a nucleus. 11. Which of the following is not an example of a nuclear reaction? A) Radioactive decay: a carbon isotope decays into a nitrogen nucleus and emits a beta particle. B) Fusion: two helium nuclei fuse to form a beryllium nucleus. C) Fission: an isotope of uranium splits into smaller nuclei when struck by a high-energy neutron. D) Oxidation: iron atoms exposed to water vapor combine with oxygen to form a reddish compound.

2 12. What is the difference between an isotope and an ion? A) An ion is created when a proton is added to a nucleus. B) An isotope is created when neutrons are added or removed from a nucleus. C) An ion is created when two isotopes fuse to form a new nucleus. D) An isotope is formed when an electron is stripped from its orbit. 13. The isotope carbon-13 can be written 13 6 C. This means that it has A) 6 protons and 13 neutrons. C) 6 protons and 7 neutrons. B) 13 protons and 6 neutrons. D) 7 protons and 6 neutrons. 14. Compare the mass and charge of carbon isotopes 12 C and 14 C. A) Both should be electrically neutral (6 protons, 6 electrons) and have the same atomic mass. B) Both should be neutral, but the 14 C should be more massive by two neutrons. C) Both should have the same mass, but the 14 C should have two extra positive charges. D) Both should have the same mass, but the 12 C should have two extra negative charges. 15. Henri Becquerel discovered A) a new element: radium. He purified it from many tons of uranium ore he inherited. B) that pitchblende contained uranium, and should therefore not be eaten as a digestive aid, which was a common practice at the time. C) that phtotographic film exposed to uranium salts became fogged, indicating that the uranium was emitting some previously undetected ray. D) that low doses of radiation were dangerous if they were repeated over long time periods. 16. Alpha decay occurs when a nucleus spontaneously emits A) a particle having two protons and two neutrons, along with a neutrino. B) an electron, after a neutron converts itself into a proton plus an electron. C) a neutron, after a proton converts itself into a neutron plus an electron. D) a neutrino only, which is the only way a nucleus can decay and still conserve energy. 17. After an alpha decay, the daughter nucleus has A) the same number of protons as the parent. C) two more protons than the parent nucleus. B) one more proton than the parent nucleus. D) two less protons than the parent nucleus. 18. Radon (Rn) is an alpha emitter. After Rn undergoes a single decay, the result is A) Po B) Po C) Ra D) Ra 19. Beta decay occurs when a nucleus spontaneously emits A) a particle having two protons and two neutrons, along with a neutrino. B) an electron, after a neutron converts itself into a proton plus an electron. C) a neutron, after a proton converts itself into a neutron plus an electron. D) a neutrino only, which is the only way a nucleus can decay and still conserve energy. 20. After a beta decay, the daughter nucleus has A) the same number of protons as the parent. C) one less proton than the parent nucleus. B) one more proton than the parent nucleus. D) two less protons than the parent nucleus. 21. Iodine is a beta emitter. After I undergoes a single decay, the result is A) Po B) Po C) Ra D) Ra 22. Which of the following nuclei is inherently unstable? A) Helium (He). B) Iron (Fe). C) Iridium (Ir). D) Astatine (At). 23. Why? A) Because any helium nucleus must have been ejected during an alpha decay, so cannot be stable. B) Because any element with an odd number of protons cannot have enough neutrons to balance the electrostatic repulsion, so these nuclei cannot maintain stability. C) All nuclei with atomic number greater than 83 are unstable. As the nucleus gets larger, the short range strong force begins to be overpowered by the long range electrostatic repulsion. D) All nuclei with atomic number less than 83 are unstable. These very light elements just don t have enough mass to be stable. Typically, they will either break down or be absorbed by heavier nuclei.

3 24. Why are there only 118 elements on the periodic table? A) Because that is how many have been discovered. There are an infinite number of elements, but you can t add them to the table before they have been discovered or created in the lab. B) Because there is an upper limit to how many protons you can have in a nucleus. Eventually the nucleus gets too big for the strong force to keep it bound together. C) Because there is an upper limit to how many neutrons you can have in a nucleus. Heavier nuclei require more neutrons, but if you add too many, they will begin to repel each other. 25. You flip a coin 10 times. At the same time, each of your three lab partners flips their coin also. A) You have flipped exactly five heads and five tails. So has each of your partners. B) You have flipped 10 heads and no tails. So has each of your partners. C) You have flipped 10 tails and no heads. Your partner flipped 10 heads and no tails. The same thing happened with your other two lab partners. D) Any of the above results are possible, but not very likely. The most likely result is that, even if you flipped more heads than tails, someone else flipped more tails than heads. No one may have flipped exactly five of each, but the average number of heads for your group is probably pretty close to five. 26. Why? A) Because according to the laws of probability, if there are only two possible outcomes for a random event, then either outcome is equally likely. You have a 50% chance of flipping heads, but you can t predict in advance which flip will fall heads. B) You do have a 50% of flipping heads, but it is not totally random. Only the first flip is random: if the first flip is heads, the next has to be tails. The flips will then alternate between heads and tails. C) Because your coin flip will affect the flip of your lab partner: if you flip heads, so will he. 27. What does this have to do with radioactive decay? A) Nothing, but like simple card tricks and juggling, you never can tell when it s going to be a handy thing to know. B) Decay is a random event; the laws of probability govern. You cannot predict in advance which nucleus will decay or exactly when. C) Decay is not really random or spontaneous. These assumptions actually over simplify the situation, which is quantum mechanical in nature. This means that it is mathematically so complex that approximating the process as random actually comes close enough. 28. Define the idea of a half-life. A) The time it takes for all of the isotopes in a sample to decay half way. For example, radon will decay into polonium, but polonium decays into lead, which is stable. The half life measure how much time it takes for all of the radon to decay into polonium. It will then take exactly the same amount of time for all the polonium to decay into lead. B) The time it takes for half of the isotopes in a sample to decay. If we use our radon sample above, we don t actually care what happens after it becomes polonium. After one half life, half of the radon has decayed. After a second half-life, half of the remaining radon will have decayed. We continue to measure the decay of the radon that remains, not the polonium that has been created. 29. You have a sample of strontium isotopes ( Sr). The half life is 30 years, and the original sample contained 2000 undecayed isotopes. After 90 years, there are how many remaining undecayed isotopes? A) B) C) 500. D) How many total years will it take before there are only about 62 undecayed isotopes left? A) 30. B) 60. C) 120. D) Why can t you use carbon dating to determine the age of non biological specimens? A) You can; there is nothing stopping you using this method to date any matter of any origin. B) Specimens that do not have a biological origin won t have processed carbon, so you have no way to know what abundance of 14 C would have been present at the creation of the sample. C) Non-biological specimens will have processed carbon until there is no 14 C left to use for dating. D) Specimens that are not biological won t contain any carbon at all. 32. Compare the penetrating ability of alpha vs. beta radiation. A) An alpha particle is more penetrating; a beta particle can be stopped by a sheet of paper. B) A beta particle can only be stopped by lead shielding about 6 thick, while alpha particles are stopped by a thickness of paper. C) A sweatshirt would be sufficient to stop either; but if bare skin is exposed, an alpha particle would barely penetrate, while the beta would penetrate to a depth of about a centimeter.

4 33. Why are gamma rays ionizing, but radio waves are not? A) They are both electromagnetic radiation, so by definition they are both ionizing. B) Radio waves have higher energy, so pass through biological cells without interacting. C) High energy gamma rays can knock electrons off individual atoms in a cell, creating ions. D) Radio waves are, in fact, ionizing. They simply are not emitted during radioactive decay. 34. What is the largest source of radiation to which a typical person is exposed? A) Cosmic rays. B) Dental x-rays. C) Radon. D) Consumer products. 35. When a neutron and proton fuse to become a hydrogen nucleus A) new nuclear energy is created. B) the existing nuclear energy is destroyed. C) nuclear energy is transformed into radiation and thermal energy. D) kinetic energy and potential energy are transformed into nuclear energy. 36. Why are fusion reactions referred to as thermonuclear? A) Because it sounds more impressive than just saying nuclear. B) In any fusion reaction, you must have some external source of heat to start the reaction. Heat is also produced during the reaction, so there is thermal energy in and thermal energy out. C) Thermo refers to the nuclear energy that is converted to heat after the fusion; if thermal energy was required to start the process, this would violate energy conservation. It can t. So it doesn t. D) Having heat on both sides of the energy equation does not violate conservation; this, however, is not what the question is asking. Thermo means heat is required to start the reaction, but no heat is given up during or after the reaction. That s why it s thermonuclear and not nucleothermal! 37. Why is thermal energy required to start a fusion reaction? A) Because of electrostatic repulsion, it is hard to get nuclei close enough for the strong force to take over and fuse them. Heat makes the nuclei move faster, which permits them to get closer. B) We just went over this. Using thermal energy to start the process would violate the principle of energy conservation. It can t. So it doesn t. C) When heat is added, atoms will tend to collect extra electrons. These negative charges will balance out the positive nuclei, and the neutral atoms can get close enough to fuse together. 38. When 1 1 H and 1 2 H fuse to become 2 3 He, the resulting helium nucleus has slightly less mass than the two hydrogen nuclei from which it formed. How is this possible? A) According to conservation of mass, it is not possible. The missing mass must be there; if you can t find it, you just are not looking hard enough. You need to double check your numbers. B) According to Einstein, E=mc 2. This means that mass and energy are actually equivalent, and matter can be turned into energy. If you balance the books, you will see that energy conservation is not violated here, and a tiny amount of the matter has been converted to energy. C) It was shown conclusively by Niels Bohr and Werner Heisenberg that nuclear processes are exempt from the conservation laws for matter and energy. It s no big deal for the mass to be missing. D) Trick question; when two hydrogen nuclei fuse, they do not make a helium nucleus. The 1 1 H fuses with a deuterium nucleus ( 1 2 H) to form a tritium nucleus ( 1 3 H), which is a heavy hydrogen isotope. 39. Why does fusion take place in the interior of stars? A) Fusion takes place all around us; it is simply more dramatic to talk about fusion in stellar cores. B) It doesn t. Stars are made of iron and heavy elements, in about the same abundances as found on earth. No fusion takes place unless the star explodes, and that process of explosion is known as fusion. C) The interior of a star is about the only place where you will find sufficiently high temperatures and pressures to start and maintain fusion reactions. D) Stars are made of heavy elements, which split (or fission) into lighter nuclei. When all of the heavy nuclei have split into iron, the star explodes. This is the supernova that ignites the fusion reaction. 40. Two copper (Cu) nuclei spontaneously fuse together to form a cerium (Ce) nucleus. True or false? A) False; copper nuclei will never be able to fuse spontaneously. They are too heavy. B) False; if two copper nuclei fuse, the result will be gallium (Ga), not cerium. C) True; this may or may not be a stable isotope, but it definitely will be cerium. D) Mostly true. Occasionally some isotopes of copper will fuse to make lanthanum (La) or praseodymium (Pr), but most of the time cerium will be formed.

5 41. Where does the iron in your blood come from? A) What kind of question is that? I suppose it comes from either red meat or fortified breakfast cereal. B) Hey, doesn t spinach have iron, too? Look at me, I m Popeye!! C) Don t pay any attention to me, I m just licking the rust off the monkey bars on the playground. D) A supernova explosion. Hey, it s no more ridiculous than answers A through C, and has the advantage of being related to this whole fusion thing we have been discussing. 42. Related how? A) Every element heavier than hydrogen has to have been created in a fusion factory. Stars create heavier elements through fusion, from hydrogen all the way up to element 118, the heaviest element. B) Close; not quite right. Stars fuse elements up to iron. A massive star will then explode, and the resulting supernova actually provides the temperatures and pressures to fuse heavier elements than iron. C) The discussion of iron is intentionally misleading. Stars fuse lighter elements into heavier ones, but 56 is the magic number: when a nucleus reaches to 56 protons (barium), it can t get any bigger. Iron has only 26 protons, so it is not relevant. 43. The first artificial radioactive isotopes were created by A) Irène and Frédéric Joliot, in They created an isotope of phosphorous. B) H.G. Well, in He documented his achievement in The World Set Free. C) Leo Szilard, working at a marine biology lab. He published The Voice of the Dolphins in D) German chemist Ida Noddack, who succeeded in creating isotopes by breaking large nuclei apart. 44. When Al is bombarded with alpha particles, one aluminum nucleus will absorb one alpha particle, and eject one neutron. The resulting isotope will be A) Na B) Al C) Al D) P 45. Who is credited with the discovery of the neutron? A) Irène Joliot-Curie, She used bombarded a uranium target with lanthanum nuclei. B) Enrico Fermi, He bombarded uranium with alpha particles and observed neutrons emitted. C) James Chadwick, He showed that certain emitted particles were uncharged, and could therefore not be protons or alpha particles. D) Albert Einstein, The theory of relativity predicts the existence of neutrons. It was not until the 1920s that Sir Arthur Eddington actually proved their existence, however. 46. Lise Meitner A) received the Nobel Prize for her PhD thesis proving the existence of stellar fusion. B) received the Nobel Prize for her work with Otto Hahn proving the existence of nuclear fission. C) performed crucial theoretical work confirming fission, but received no Nobel acknowledgement. D) was an outdoor enthusiast and the Swedish girlfriend of Otto Frisch. He performed the important work proving fission, and shared the Nobel Prize with Otto Hahn. 47. How does a fission reaction occur? A) Two nuclei collide, and fuse to form a heavier nucleus. The new, heavy nucleus is unstable, and will soon split apart. The fission is never spontaneous, it will always be preceded by an initial fusion. B) A nucleus spontaneously breaks apart. This is much like an alpha decay, but the fission fragments are much larger than helium nuclei, so it has a different name. C) A nucleus splits apart. This is different from alpha decay because it will not happen spontaneously. Typically, it will occur when a nucleus is bombarded with energetic neutrons that disrupt the stability and permit the electrostatic repulsions to push large fragments apart. D) It is called fission because it actually is kind of fizzy, like the bubbles that rise when you pour a can of soda into a glass. The bubbles in a fission reaction are not alpha, but beta particles that are spontaneously emitted when a fissionable material is disturbed. 48. Explain the concept of a chain reaction. A) When a nucleus splits, an ejected neutron collides with a second nucleus. This causes the second nucleus to split, and it ejects a neutron. The result is a cascade of nuclear fission as more neutrons are ejected and collide with more nuclei. B) An alpha particle collides with a nucleus, and is absorbed. Subsequently, a beta particle is emitted. The chain of alternating alpha absorptions and beta emissions creates heavier and heavier nuclei, until a critical mass is reached and the whole thing explodes violently (this is a lot like a supernova explosion, but on a much smaller scale). C) Backwards! The chain reaction is beta absorptions followed by alpha emissions. A nucleus gets lighter with each emission, not heavier. The lighter nuclei want to expand, but are constrained by a shell of heavy metal. This creates a growing pressure until a critical mass of nuclei are so light that the pressure bursts the shell, and the whole thing explodes but not like a supernova at all.

6 49. The heaviest naturally occurring element is A) 118 (nameless). B) 109, Meitnerium. C) 92, Uranium. D) 86, Radon. 50. What is the difference between 238 U and 235 U? A) 238 U and 235 U are both stable, naturally occurring isotopes of uranium. No appreciable difference. B) 238 U is naturally occurring and 235 U must be created artificially. Both are stable isotopes. C) 238 U is common and stable, but 235 U is rare and highly fissionable. Both occur naturally. D) 238 U is rare and highly fissionable, but 235 U is common and stable. Neither occurs naturally.

Chapter 3. Radioactivity. Table of Contents

Chapter 3. Radioactivity. Table of Contents Radioactivity Table of Contents Introduction 1. Radioactivity 2. Types of Radioactive Decays 3. Natural Radioactivity 4. Artificial Radioactivity 5. The Rate of Radioactive Decay 6. The Effects of Radiation