10.4 Fission and Fusion
Reading Focus
Key Concepts
Under what conditions does the strong nuclear force overcome electric forces in the nucleus?- What property of fission makes it so useful?
Vocabulary
strong nuclear force
fission
chain reaction
critical mass
fusion
plasma
Reading Strategy
Comparing and Contrasting Copy the Venn diagram below. As you read, contrast fission and fusion by listing the ways they differ.
Alternative energy sources may someday replace fossil fuels such as coal and oil. One alternative energy source that is widely used today is nuclear energy. Nuclear energy is the energy released by nuclear reactions.
Shortly after the discovery of radioactivity, scientists realized that atomic nuclei contained vast amounts of energy. By the late 1930s, scientists discovered that transmutations involved more than just the conversion of one element into another—they also involved the conversion of mass into energy.
Figure 15 Two kinds of forces act upon particles in the nucleus. Strong nuclear forces, which are attractive, act on protons and neutrons alike. Electric forces in the nucleus are repulsive, and act only among protons.
Using Models What atomic nucleus is represented above?
dNuclear Forces
What holds the nucleus together? Remember that the protons in the nucleus are all positively charged, so they tend to repel one another. Clearly, there must be an attractive force that binds the particles of the nucleus. Otherwise, the protons would simply push one another away.
The strong nuclear force is the attractive force that binds protons and neutrons together in the nucleus. Because the strong nuclear force does not depend on charge, it acts among protons, among neutrons, and among protons and neutrons. Over very short distances, the strong nuclear force is much greater than the electric forces among protons. For example, at distances as short as the width of a proton, the strong nuclear force is more than 100 times greater than the electric force that repels protons. However, the strong nuclear force quickly weakens as protons and neutrons get farther apart. Figure 15 summarizes the forces acting on protons and neutrons in the nucleus.
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