NAME:___________________________________ DATE:_______SECTION_____LAB_____
Its All Going Away
Background:
Elements such as uranium, thorium, and plutonium are observed to emit particles and thereby
undergo radioactive decay. By emitting particles, the original (or parent) element alters its
composition to another element known as the daughter element. If the daughter element is also
radioactive, then it will emit a particle and decay into yet another daughter element. The decay
process continues until the final daughter product is no longer radioactive.
The emitted particles are known as: alpha, beta, and gamma. Alpha particles have a positive
charge, an atomic mass of 4, and are essentially a helium atom without any electrons. Beta
particles have a negative charge, an atomic mass of 0, and are electrons. Gamma rays are highenergy rays that are emitted by nearly all radioactive materials and have no mass or charge.
Objective:
To create a graph of the decay series for Uranium-238.
Procedure:
1) On your data table shown to the
right calculate each stage of the
decay’s mass number and proper
nuclide symbol.
2) Label your y-axis number of
neutrons. Create a scale going
from 120 to 150.
Number of
Protons
Number of
Netrons
Mass
Number
Nuclide Symbol
92
146
238
U-238
90
144
91
143
92
142
3) Label your x-axis number of
protons (Atomic Number). Create
a scale going from 80 to 94.
90
140
88
138
4) Plot each point on your graph.
86
136
5) Label each point with its correct
symbol.
84
134
82
132
83
131
84
130
82
128
83
127
84
126
82
124
6) Draw an arrow between each
points to show the flow of the
decay.
7) Label each arrow with the proper
alpha or beta symbol.
Reflection:
Describe why a radioisotope would undergo a decay series.
Questions:
1) At which element does U-238’s decay series end?
2) Why does the decay series end where it does?
3) During each decay what occurs to the proton to neutron ratio?
4) Describe what happens to the number of protons and neutrons during alpha decay?
5) Describe what happens to the number of protons and neutrons during beta decay?
Use the following decay equation to answer questions 6 to 9.
6) Which isotope is the parent ____________
7) Which isotope is the daughter___________
8)
(1)
(2)
(3)
(4)
Which type of decay is shown?
Alpha
Beta
Gamma
Positron
9) In the space below write an equation for the beta decay of Pa-234.
10) Write down which type of decay that occurs along this sequence.
11) You create the decay series for 250Bk.
β
Bk97 
250
α

β

250
Cf98
α

β

α

α

α

α

α

α

α

β

β

α

β

β

α

Use the following passage to answer questions 12 to 14
In nuclear physics, a magic number is a number of nucleons (either protons or neutrons) such
that they are arranged into complete shells within the atomic nucleus. The seven most widely
recognized magic numbers are 2, 8, 20, 28, 50, 82, 126.
Atomic nuclei consisting of such a magic number of nucleons have a higher average binding
energy per nucleon and are hence more stable against nuclear decay.
Nuclei which have both neutron number and proton (atomic) number equal to one of the magic
numbers are called "double magic", and are especially stable against decay.
12) Which of the isotopes in the decay series of Uranium-238 contains a magic number?
(1) U-238
(2) Th-234
(3) Po-210
(4) Bi-210
13) Which isotope of lead has a double magic number?
(1) Pb-206
(2) Pb-207
(3) Pb-208
(4) Pb-209
14) Which list contains elements all with a magic number of protons?
(1) H, He, Ca, Fe
(2) He, Co, Ge, Sn
(3) He, O, Sn, Pb
(4) O, Ca, Os, Bi