Chapter19

Fluorine has an atomic number of 9 and an atomic weight of approximately 19. How many neutrons would you expect to find in the nucleus of the most common isotope of fluorine? ____neutrons

10

Suppose that we have 89,000 atoms of a radioactive substance with a half-life of 20 minutes. (a) How many atoms of that element remain after 100 minutes? ____atoms (b) How many atoms remain after 8 hours? ____atoms

2781 5.3e-3

How many half-lives must be go by for the radioactivity of a given isotope to drop to one-sixteenth of its original values? ___half-life How many half-lives must go by for the radioactivity of a given isotopes to drop to on-sixty-fourth 六十四分之一 of its original value ___half-lives

4 6

44Ru96 is an isotope produced in nuclear reactors. (a) How many protons are in the nucleus of this isotope? ___protons (b) How many neutrons are in the nucleus of this isotope? ___neutrons

44 52

1. The three types of nuclear radiation are A. gamma, beta, alpha. B. radiation, convection, conduction. C. electrical, strong nuclear, weak nuclear. D. protons, electrons, neutrons.

A

23. Energy released in a nuclear fission process is produced by A. conversion of some mass to energy. B. electrons moving from a higher energy orbit to a lower energy orbit. C. the conversion of gravitational potential energy into kinetic energy. D. the conversion of some charge to energy.

A

27. A deuterium nucleus and a tritium nucleus react to yield one alpha particle, a neutron, and energy. For this reaction, the sum of the masses of reaction products after the reaction is __________ the sum of the masses of particles before the reaction. A. less than B. greater than C. equal to

A

32. A sample of U235 that is below the critical mass will not sustain a chain reaction because A. too many neutrons escape through the surface of the sample without initiating fission. B. the heat produced by the spontaneous fission of some nuclei is insufficient C. nuclei repel each other due to their positive charges. D. the inertia of the sample is too low for efficient fission.

A

38. Consider two different samples of radioactive isotopes, one naturally occurring and the other artificially produced. If the samples have the same number of nuclei, then A. the one with the shorter half-life is likely more dangerous. B. the one with the smaller atomic mass is likely more dangerous. C. the artificially produced one is likely more dangerous. D. they are equally dangerous.

A

42. A piece of uranium can be made into nuclear explosive only after it is purified into uranium-235, because A. the other naturally occurring isotopes of uranium interfere with efficient chain reactions. B. uranium-235 is the heaviest isotope known to mankind. C. before purification, the uranium-235 nucleus will not split apart. D. it has to be soldered with lead for safety.

A

44. The instability of uranium-235 compared to uranium-238, along with the relative stability of hydrogen compared to tritium, shows that the stability of a given nucleus depends upon A. adding or subtracting neutrons, which can change a stable isotope into an unstable isotope. B. the mass: heavier nuclei are always less stable. C. the number of electrons in the nucleus. D. the speed of electrons orbiting the nucleus: more mass means more gravitational pull.

A

6. The "beta" particle is A. an electron. B. electromagnetic radiation. C. two electrons bound to two neutrons. D. a helium nucleus.

A

The primary useful product of nuclear reactors designed for power generation is A. high pressure steam B. radioactive materials C. graphite D.enriched uranium

A

17. In a nuclear reactor, "chain reaction" refers primarily to A. the production of plutonium from uranium B. the role of neutrons in the initiation and continuation of nuclear fission. C. the bonding of radioactive nuclei. D. the separation of uranlum-235 from uranlum-238

Answer:B

10. A nucleus undergoes beta decay. Which of the following statements is true? A. The daughter element has fewer protons than the parent. B. The daughter element has more protons than the parent. C. The daughter element has the same number of protons as the parent. D. Both daughter and parent elements have the same atomic number.

B

15. In nuclear fission, A. two heavy nuclei are induced to decay simultaneously. B. a nucleus is split into two less massive nuclei. C. a nucleus is bombarded with another nucleus in order to induce an alpha decay. D. high-energy particles are released from a nucleus that is at rest.

B

2. The word "radioactive" means A. there is significant interference between atomic radiation and radio reception. B. there are nuclei present which will spontaneously emit nuclear radiation. C. an atom spontaneously captures an electron from a neighboring atom. D. an atomic nucleus absorbs neutrons.

B

20. In nuclear fusion, A. a large nucleus splits into smaller fragments. B. two smaller nuclei combine to form a larger nucleus. C. many radioactive nuclei decay at once. D. the temperatures required are so high that it has never been accomplished on Earth.

B

26. A deuterium nucleus and a tritium nucleus react to yield one alpha particle, a neutron, and energy. This is an example of a A. fission reaction. B. fusion reaction. C. chemical reaction. D. chain reaction.

B

30. Both conventional fossil fuel and nuclear power plants A. produce carbon dioxide, which may increase global warming. B. produce waste heat that can affect the weather or upset the ecology of rivers or lakes. C. produce hazardous waste products that must be stored in isolation for thousands of years. D. contribute to the problem of acid rain.

B

37. Two atoms have the same number of neutrons but different numbers of protons. These two atoms A. are isotopes of each other. B. will exhibit different chemical properties. C. have the same atomic mass. D. have the same number of electrons.

B

40. A feature of the nuclear reactor at Chernobyl that contributed to the magnitude of the accident there was that A. the uranium fuel was more highly enriched. B. water was used only as a coolant, not a moderator. C. plutonium could build up quickly in the reactor. D. the reactor did not have control rods.

B

45. Momentum and energy from focused laser beams can be used in nuclear fusion. This has an advantage over magnetic confinement reactors in that A. light is not magnetic. B. light cannot be melted, so its pressure can confine the reaction. C. the wavelength of light is small enough to penetrate each proton. D. light can also function as a moderator, like graphite or water in a uranium reactor.

B

7. A "gamma" ray is A. an electron. B. electromagnetic radiation. C. two electrons bound to two neutrons. D. a helium nucleus.

B

8. During radioactive decay, the daughter element is always A. more massive than the parent. B. less massive than the parent. C. the same mass as the parent. D. None of these.

B

9.When a nucleus undergoes alpha decay, the daughter element always has A. more neutrons than the parent. B. less mass than the parent. C. the same atomic number as the parent. D. more electrons than the parent.

B

Thorium-229 undergoes alpha decay. Complete the reaction equation for this decay and identify the daughter nucleus. 90Th229 ? + α A.88Ra227 B.88Ra225 C.90Ra229 D.86Ra225

B

11. The "half-life" of a large collection of radioactive nuclei is A. the number of nuclei that decay in 1 second. B. the number of nuclei that remain after 1 second. C. the time for half of the collection to decay. D. larger for heavy nuclei than for lighter nuclei.

C

14. What is the source of the energy released in nuclear reactions? A. The conversion of nuclear kinetic energy to particle potential energy. B. Heat released during the radioactive decay process. C. The conversion of mass to energy. D. The binding of orbital electrons to the nuclear protons.

C

18. The substance that comes from a nuclear reactor which can be used to generate power is A. enriched uranium. B. graphite. C. high-pressure steam. D. radioactive materials.

C

22. Two nuclei have the same number of protons but different numbers of neutrons. We call these two nuclei A. ions. B. isotopes. C. isobars. D. atomic mass units.

C

24. In a decay of 90Th232 by emission of an alpha particle, the daughter nucleus will be A. 90Th228. B. 92U232. C. 88Ra228. D. 88Ra230. E. 87Ac232.

C

25. Generally, the number of neutrons present in nuclei that are fission fragments is ________ the number of neutrons of corresponding nuclei of stable isotopes. A. equal to B. less than C. greater than

C

28. In a modern light water reactor, the ratio of U235 to U238 in the nuclear fuel is typically in the approximate ratio of A. 0.7:99.3. B. 1:1. C. 3:97. D. 10:90. E. 40:60.

C

29. The purpose of the moderator in a reactor is to A. provide cooling for the control rods. B. reduce the number of neutrons available for the chain reaction. C. slow neutrons down so that they will be more likely to initiate fission reactions. D. separate the nuclear fuel from the spent products of fission.

C

31. The primary reason that nuclear fusion has proven difficult to adapt for commercial power generation is that A. the possible fuel is scarce. B. the fuel is difficult to purify. C. nuclei repel each other due to their positive charges. D. the temperatures involved are too low for efficient production.

C

34. Walther Bothe and Wilhelm Becker discovered a new kind of particle radiation in 1930. The particle was later determined to be a neutron. Bothe and Becker generated neutron radiation by A. using an isotope that decays by emitting neutrons. B. heating nuclei to extremely high temperatures to boil the neutrons off. C. firing a beam of alpha particles at a beryllium target. D. using electrons to attract protons away from the nucleus.

C

39. In a nuclear fission reaction, A. one nucleus splits into two equal halves. B. one nucleus splits into two parts, one very small and one almost the same mass as the parent. C. one nucleus splits into two parts, neither daughter having a mass close to the parent. D. two nuclei combine to form a single, more massive nucleus.

C

4. The number of protons in the nucleus of an atom determines A. the number of neutrons in the nucleus. B. the half-life of the nucleus. C. the density of the nucleus. D. the chemical properties of the atom.

C

43. The atomic mass system is based upon A. the mass of the neutron. B. the mass of uranium-238, since it is the heaviest element occurring in nature. C. the mass of carbon-12, a very common isotope of carbon. D. the mass of liquid water.

C

How might one generate a beam of neutrons? A.Find a naturally radioactive substance that emits neutrons. B.Heat a beam of protons with a laser. C.Fire a beam of alpha particles at a beryllium target. D.Pass a beam of alpha particles through an electric field to remove the protons.

C

Suppose that we discover that one of the fission fragments for a given fission reaction of uranium-235 is tin-130 and that four neutrons are emitted in this reaction. Complete the reaction equation and identify the other fission fragment. 0n1 + 92U235 ? + 50Sn130 + 4 0n1 A.39Y102 B.39Y135 C.42Mo102 D.42Mo135

C

12. Which of the following mechanisms can change the half-life of radioactive nuclei? A. Extreme high pressure. B. Extreme high temperature. C. Increasing the number of nuclei in the sample. D. None of these

D

13. A nucleus undergoes radioactive decay, emitting a gamma ray. Which of the following statements is true? A. The daughter nucleus has more neutrons than the parent. B. A nuclear proton changes into an electron-positron pair. C. Both daughter and parent nuclei have the same atomic number. D. The daughter nucleus is more massive than the parent.

D

16. The separation of different isotopes of a particular element can be difficult because A. the masses of the isotopes are the same. B. all isotopes are dangerous because of their radioactivity. C. neutrons are so small. D. chemical reactions happen the same way for the isotopes.

D

19. A primary waste product of nuclear reactors designed for power generation is A. graphite. B. high-pressure steam. C. enriched uranium. D. radioactive materials.

D

21. The N14 nucleus consists of A. 14 neutrons. B. 14 protons. C. 21 protons and 7 electrons. D. 7 protons and 7 neutrons.

D

3. The discovery of the neutron helped people understand A. why the nucleus has a positive charge. B. how electrons are attracted to the nucleus. C. why the nucleus is much more massive than the electrons in an atom. D. how two atoms of the same element can have different atomic masses.

D

33. The average U.S. citizen receives measurable radiation from man-made sources such as power plants, medical and dental X-rays, and consumer products. The radiation received from natural sources is A. almost immeasurable. B. measurable but less than that received from artificial sources. C. about the same as that received from artificial sources. D. more than that received from artificial sources.

D

35. The Tokamak is a type of A. nuclear reactor using graphite as a moderator, such as the reactor at Chernobyl. B. moderator used in pressurized heavy water reactors. C. particle accelerator. D. experimental fusion reactor.

D

36. The number of neutrons in a stable isotope must A. equal the number of protons. B. equal the number of electrons. C. equal the number of protons plus electrons. D. None of the choices is correct.

D

41. In all nuclear reactions, A. charge is not created or lost. B. the total number of protons plus neutrons must be conserved. C. energy must be conserved. D. all of these.

D

46. Neutrons were discovered by James Chadwick by observing the behavior of A. gold atoms in a thin foil. B. copper conducting electricity in the absence of a magnetic field. C. carbon dioxide molecules under high pressure. D. the collision after-effects of protons emerging from paraffin.

D

5. The "alpha" particle is A. two protons bound to two neutrons. B. two electrons bound to two protons. C. two electrons bound to two neutrons. D. a helium nucleus

D

A nucleus undergoes radioactive decay, emitting a gamma ray. Which of the following statements is true? A. The daughter nucleus has fewer protons than the parent. B. The daughter nucleus is more massive than the parent. C. A nuclear proton changes into a neutron-electron pair. D. Both daughter and parent nuclei have the same atomic number.

D

The separation of different isotopes can be done by A.process based on the different chemical properties of the isotopes. B. rapid bombardment of uranium by slow neutrons C. moderating the isotopes with carbon rods. D. processes based on the different physical properties of the isotopes.

D

Two isotopes of the same element will have A. the same atomic mass. B. different numbers of protons in the nucleus. C. different chemical properties D. different atomic masses.

D

The chemical properties of an atom are determined by A. the net charge on the atom B. the mass number of the nucleus c. the number of neutrons in the nucleus D. the half-life of the nucleus. E. the number of protons in the nucleus.

E