Book Cover Chemistry 8th Edition / Chang
Student Study Guide

Chapter 23: Nuclear Chemistry


Index | 23.1 | 23.2 | 23.3 | 23.4 | 23.5 – 23.6 | 23.8 |

THE NATURE OF NUCLEAR REACTIONS (23.1)

STUDY OBJECTIVES
  1. Write balanced nuclear equations for radioactive decay and nuclear transmutation processes.
  2. Compare chemical reactions and nuclear reactions.

Nuclear Reactions and Nuclear Equations. This chapter emphasizes changes that occur within the nucleus of an atom. To begin, we will discuss two types of nuclear reactions: radioactive decay and nuclear transmutation. Radioactivity is described as the spontaneous emission of particles and/or radiation by unstable atomic nuclei. These processes often result in the formation of a new element. The kinds of particles emitted from various nuclei are shown in Table 23.1.

Table 23.1 Particles From Radioactive Decay

A nucleus can also undergo change by nuclear transmutation. In this process a nucleus reacts with another nucleus, an elementary particle, or a photon (gamma particle) to produce one or more new nuclei.

Radioactive decay and nuclear transmutation processes are described by nuclear equations. These equations use isotopic and elementary particle symbols to represent the reactants and products of nuclear reactions. For example, in the first nuclear transmutation ever observed (in 1919) alpha particles were used to bombard nitrogen-14 nuclei. The observed products were atoms of oxygen-17 and protons. The nuclear equation is

The balancing rules for nuclear equations are given below and are applied to the above equation:

  1. The sum of the mass numbers of the reactants must equal the sum of the mass numbers of the products (conservation of mass number). 14 + 4 = 18 = 17 + 1
  2. The sum of the nuclear charges of the reactants must equal the sum of the nuclear charges of the products (conservation of atomic number). 7 + 2 = 9 = 8 + 1

These rules will be illustrated further in the example problems.

EXAMPLE Nuclear Equations

Complete the following nuclear equations.

a.

b.

Comparison of Chemical and Nuclear Reactions. visual aid Table 23.1 of the text lists a number of comparisons between chemical and nuclear processes. Keep in mind that in chemical reactions the number of atoms of each element is conserved. Only changes in chemical bonding occur. However, in nuclear reactions the composition of the atomic nucleus is altered, and so elements are converted from one to another. Since a nucleus is so extremely small, and in some cases contains large numbers of positively charged protons, the energy changes associated with nuclear changes are much greater than energy changes in chemical reactions.

OBJECTIVE CHECK

Complete the following questions to check your understanding of the material. Select the check button to see if you answered correctly.

  1. Write symbols for alpha particles, beta particles, and gamma rays.
    2. alpha a
    beta b
    gamma g
  2. How many protons (p), neutrons (n), and electrons (e) does an atom of the radioisotope phosphorus-32 contain?
    p =
    n =
    e =
  3. Complete the following nuclear reactions:
    a.
    b.
    c.
    d.
  4. When a nucleus decays by positron emission, the atomic number of the decay product will be than the original radioisotope.

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