Nuclear Chemistry
Atomic Structure and Nuclear Chemistry
Part I: What’s My Radiation Type?
What keeps protons and neutrons together in the nucleus of an atom? If protons are positively
charged, shouldn’t they be repelling each other and causing all the protons to be moving away
from each other?
neutrons
Nucleons - held together
by nuclear binding energy
protons
The force that keeps protons and neutrons together in the nucleus is called the nuclear binding
energy. It is large enough to overcome the repulsive electrostatic forces of the protons that want to
push the protons apart. The table below shows several common, stable atoms. What do they have
in common? Complete the rest of the table in your Student Journal.
Symbol
Atomic
mass
Atomic
number
# of
protons
# of
neutrons
Ratio of protons
to neutrons
He
4
2
2
2
1:1
C
12
6
6
6
1:1
N
14
7
7
7
1:1
O
16
8
8
8
1:1
F
19
9
Ne
20
10
Na
23
11
Pb
207
82
The larger the atom becomes, the larger is its proton to neutron ratio. As this ratio increases, the
atom becomes unstable. It will release particle to achieve stability and thus become radioactive.
Atoms greater than 207 82Pb are usually radioactive.
Continue to the next page.
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Nuclear Chemistry
Atomic Structure and Nuclear Chemistry
Part I: What’s My Radiation Type?, continued
Writing Nuclear Equations
Nuclear decay is a type of nuclear reaction that involves the nucleus of an unstable, radioactive
atom emitting alpha, beta, and/or gamma particles in order to become a more stable atom. A
nuclear equation is a representation of a nuclear reaction. Unlike a chemical equation, a nuclear
equation is written showing only the nuclei of the reactants and products.
There is a special way to write the reactants and products of a nuclear equation using the chemical
symbol and the mass and atomic number. These numbers are critical as they demonstrate how
mass is conserved in the reaction. The mass number of the element is written higher and to the left
of the element symbol, and the atomic number is written below the mass number.
Mass number
Atomic number
220
86 Rn Element Symbol
The sum of the mass numbers of the reactants must equal the sum of the mass numbers for the
products. The same applies for the atomic numbers, which demonstrates the Law of Conservation
of Mass. The new element produced in the nuclear reaction is determined by the atomic number of
the new element after the equation is balanced. Two kinds of nuclear decay reaction equations are
shown below:
Alpha decay: A radioactive element emitting an alpha particle (helium nuclei)
reactants
products
Conservation of Mass
224 220 4 88 Ra ! 2 He + 86Rn Radioactive
element
α particle
New
element
Mass number 224 = 4 + 220
Atomic number 88 = 2 + 86
Beta decay: A radioactive element emitting an beta particle (an electron)
14 14 0 6 C ! 7 N + -­‐1 β Radioactive
element
New
element
β particle
Mass number 14 = 14 + 0
Atomic number 6 = 7 + -1
Continue to the next page.
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Nuclear Chemistry
Atomic Structure and Nuclear Chemistry
Part I: What’s My Radiation Type?, continued
In this activity, you will explore the different kinds of radiation, what they are used for, what their
characteristics are, and how to balance nuclear equations.
Procedure:
1.  Obtain the Student Reference Sheet: Radiation Reference information from your teacher for
each of the three types of radiation. Distribute among the members of your group.
2.  Write down the type of radiation you will be researching. Each group member will learn about
one of the three types of radiation.
3.  Write a Question of Inquiry about what you think you will find out from your group’s research.
4.  Examine the properties of the type of radiation presented to you in the reference sheets. Here
are some characteristics to look for:
1. 
2. 
3. 
4. 
What are the radioactive particles made of?
What electrical charge does each particle have?
What is the symbol for each form of radiation?
What types of barriers are used to stop the different types of radiation?
5.  Describe the type of radiation assigned to you. Sketch a picture showing its composition.
Include subatomic particles.
6.  Share what you have learned about your type of radiation with your group members. Then
listen to what they have learned about the radiation type they researched.
7.  Draw the path each type of radiation will take as it emerges from the source and is exposed to
an applied electric field. How will the charge of each radiation type affect its path through the
electric field?
8.  Complete the nuclear equations in your Student Journal.
Complete Part I of your Student Journal.
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Nuclear Chemistry
Atomic Structure and Nuclear Chemistry
Part II: Radioactivity and Medicine
You will investigate how radioactive isotopes are used to diagnose and treat diseases.
Procedure:
1.  Obtain the Isotope Reference Sheets in the Student Reference Sheet: Radiation Reference,
which describe different radioactive isotopes used in nuclear medicine. Distribute one to each
group member to research, and use Part II of your Student Journal to summarize your findings.
2.  Begin by identifying your radioactive isotope and the treatment it is used for.
3.  Identify how your radioactive isotope is produced.
4.  Each isotope has a characteristic time span before half of it decays to a more stable form. As
this time span progresses, less and less of the radioactive isotope remains for medical
treatment or diagnosis. Identify this time span, or half-life, of your radioactive isotope.
5.  Write the nuclear equation that shows how your isotope decays to a more stable state using
element or particle symbols, mass numbers, and atomic numbers.
Part III: Nuclear Decay
You will trace the path of an unstable radioactive isotope until it reaches a stable form.
Obtain a Decay Series Card to research. Once you have it, use Part III of your Student Journal to
write each product of the decay series on the chart provided until a stable isotope is reached. The
product of the first reaction becomes the reactant in each subsequent reaction. If needed, use a
separate piece of paper to write out the equations that occur in each step. You will have as many
equations as there are transitions listed in the decay series.
Complete Part II and III of your Student Journal.
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