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246 Chemistry: Matter and Change
Solving Problems: A Chemistry Handbook
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 24
Practice Problems
1. What element is formed when each of the following radioisotopes undergoes alpha decay? Give the atomic number and
mass number of the element.
a. polonium-212 ( 212
84 Po)
c. uranium-238 ( 238
92 U)
b. astatine-218 ( 218
85 At)
d. polonium-214 ( 214
84 Po)
Beta radiation is a stream of beta particles (electrons). An
example of the beta decay of iodine-131 is shown below.
131
53 I 0 131
54 Xe ϩ Ϫ1
0 
Iodine-131 0 Xenon-131 ϩ Beta particle
Notice that the mass number does not change. However, the atomic
number increases by 1 (54 instead of 53), changing the identity of
the element.
The emission of a gamma ray does not change the atomic number or the mass number of a nucleus. Gamma rays almost always
accompany alpha and beta radiation. In fact, gamma rays account for
most of the energy that is lost during radioactive decay. Because
gamma rays have no effect on the atomic number or the mass number of a nucleus, it’s customary to leave them out of nuclear
equations.
Practice Problems
2. What element is formed when each of the following radioisotopes undergoes beta decay? Give the atomic number and mass
number of the element.
a. 3
1 H
b. 235
92 U
c. 60
26 Fe
d. 234
90 Th
24.2 Radioactive Decay
About 17 percent of known isotopes are stable. The rest decay spontaneously. The neutron-to-proton (n/p) ratio of the nucleus is a
primary factor in determining the type of radioactive decay a
radioisotope will undergo. The nucleus, which contains most of an
atom’s mass, is made up of positively charge protons and neutral
neutrons. Both protons and neutrons are called nucleons. Protons
stay packed in the nucleus despite their strong electrostatic repulsion
246 Chemistry: Matter and Change
Solving Problems: A Chemistry Handbook
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 24
Practice Problems
1. What element is formed when each of the following radioisotopes undergoes alpha decay? Give the atomic number and
mass number of the element.
a. polonium-212 ( 212
84 Po)
c. uranium-238 ( 238
92 U)
b. astatine-218 ( 218
85 At)
d. polonium-214 ( 214
84 Po)
Beta radiation is a stream of beta particles (electrons). An
example of the beta decay of iodine-131 is shown below.
131
53 I 0 131
54 Xe ϩ Ϫ1
0 
Iodine-131 0 Xenon-131 ϩ Beta particle
Notice that the mass number does not change. However, the atomic
number increases by 1 (54 instead of 53), changing the identity of
the element.
The emission of a gamma ray does not change the atomic number or the mass number of a nucleus. Gamma rays almost always
accompany alpha and beta radiation. In fact, gamma rays account for
most of the energy that is lost during radioactive decay. Because
gamma rays have no effect on the atomic number or the mass number of a nucleus, it’s customary to leave them out of nuclear
equations.
Practice Problems
2. What element is formed when each of the following radioisotopes undergoes beta decay? Give the atomic number and mass
number of the element.
a. 3
1 H
b. 235
92 U
c. 60
26 Fe
d. 234
90 Th
24.2 Radioactive Decay
About 17 percent of known isotopes are stable. The rest decay spontaneously. The neutron-to-proton (n/p) ratio of the nucleus is a
primary factor in determining the type of radioactive decay a
radioisotope will undergo. The nucleus, which contains most of an
atom’s mass, is made up of positively charge protons and neutral
neutrons. Both protons and neutrons are called nucleons. Protons
stay packed in the nucleus despite their strong electrostatic repulsion