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CHAPTER 16: 1, 3, 4, 5, 7, 9, 11, 14, 17, 18, 19, 22, 24, 25, 26, 36, 42, 48, 50.
1.Radioactivity is a part of nature, going back to the beginning of time.
3. A radioactive sample is always a little warmer than its surroundings because the radiating alpha or beta
particles impart internal energy to the atoms of the sample. (Interestingly enough, the heat energy of the Earth
originates with radioactive decay of the Earth’s core and surrounding material.)
4. It is impossible for a hydrogen atom to eject an alpha particle, for an alpha particle is composed of a pair of
hydrogen isotopes (deuterium). It is equally impossible for a 1-kilogram melon to spontaneously break into
four 1-kilogram melons.
5. Alpha and beta rays are deflected in opposite directions in a magnetic field because they are oppositely
charged—alpha are positive and beta negative. Gamma rays have no electric charge and are therefore
undeflected.
7. The alpha particle has twice the charge, but almost 8000 times the inertia (since each of the four nucleons has
nearly 2000 times the mass of an electron). Hence it bends very little compared to the much less massive beta
particles (electrons). Gamma rays carry no electric charge and so are not affected by an electric field.
9. Gamma radiation produces not only the least change in mass and atomic numbers, but produces no change in
mass number, atomic number, or electric charge. Both alpha and beta radiation do produce these changes.
11. The proton “bullets” need enough momentum to overcome the electric force of repulsion they experience once
they get close to the atomic nucleus.
14.The fusing of hydrogen atoms into helium atoms suggests that the electric force of repulsions can be overcome
by the strong nuclear force if two atomic nuclei are able to get close enough to each other.
17. When radium (A = 88) emits an alpha particle, its atomic number reduces by 2 and becomes the new element
radon (A = 86). The resulting atomic mass is reduced by 4. If the radium were of the most common isotope
226, then the radon isotope would have atomic mass number 222.
18. After beta emission from polonium, the atomic number increases by 1 and becomes 85, and the atomic mass is
unchanged at 218. However, if an alpha particle is emitted, the atomic number decreases by 2 and becomes
82, and the atomic mass decreases by 4 and drops to 214.
19. Deuterium has 1 proton and 1 neutron; carbon has 6 protons and 6 neutrons; iron has 26 protons and 30
neutrons; gold has 79 protons and 118 neutrons; strontium has 38 protons and 52 neutrons; uranium has 92
protons and 146 neutrons.
22. The Earth’s natural energy that heats the water in the hot spring is the energy of radioactive decay, which
keeps the Earth’s interior molten. Radioactivity heats the water, but doesn’t make the water itself radioactive.
The warmth of hot springs is one of the “nicer effects” of radioactive decay. You’ll most likely encounter more
radioactivity from the granite outcroppings of the foothills than from a nearby nuclear power plant.
Furthermore, at high altitude you’ll be exposed to increased cosmic radiation. But these radiations are not
appreciably different than the radiation one encounters in the “safest” of situations. The probability of dying
from something or other is 100%, so in the meantime we all should enjoy life anyway!
24. Gamma radiation is generally the most harmful radiation because it is so penetrating. Alpha and beta radiation
is dangerous if you ingest radioactive material, which is comparatively uncommon.
25. Film badges monitor gamma radiation, which is very high-frequency X-rays. Like photographic film, the
greater the exposure, the darker the film upon processing.
26. You can tell your friend who is fearful of the radiation measured by the Geiger counter that his attempt to
avoid the radiation by avoiding the instrument that measures it, is useless. He might as well avoid
thermometers on a hot day in an effort to escape the heat. If it will console your fearful friend, tell him that he
and his ancestors from time zero have endured about the same level of radiation he receives whether or not he
stands near the Geiger counter. There are no better options.
36. U-235 isn’t in concentrated form in ordinary uranium ore.
42. To predict the energy release of a nuclear reaction, simply find the difference in the mass of the beginning
nucleus and the mass of its configuration after the reaction (either fission or fusion). This mass difference
(called the “mass defect”) can be found from the curve of Figure 16.33 or from a table of nuclear masses.
Multiply this mass difference by the speed of light squared: E = mc2. That’s the energy released!
48.The hydrogen that can be used as fuel is molecular hydrogen, H 2, which can be created from our planet’s vast
supply of water, H2O. As will be explored in future chapters, however, to convert water into molecular
hydrogen requires the input of energy from some source, such as solar, nuclear, or fossil fuel. The great
advantage of hydrogen is that it is a very clean carrier of energy because burning produces only water vapor.
50. Both fossil fuel and nuclear fission power plants produce pollution. The fossil-fuel pollution is primarily in the
form of air pollution. Nuclear-fission power plants produce very little air pollution, but they generate large
quantities of radioactive wastes, which are typically liquid or solid.