When learning about atomic structure students usually also
learn about isotope notation. To give a full description of
the make-up of an isotope it isn’t necessary to write
out a sentence. A simple symbol will do. The symbol works
like this: ^{A}_{Z}X,
where A stands for the mass number and gives the sum of the
number of protons and neutrons in the nucleus. And Z stands
for the atomic number, which equals the number of protons
in a nucleus. It does not give the number of
electrons, which can vary. The letter X stands in for any
atomic symbol in the periodic table.
Fill in the following table with the required
information about the isotopes in the picture at left.
Name
Symbol
p^{+}
n^{0}
Mass
hydrogen-1
^{1}_{ 1}H
1
0
1
hydrogen-2
^{2}_{ 1}H
Model 1
Which color is used for protons
in Model 1? Which color is used for neutrons?
What is the meaning of the
letter ‘Z’ when speaking about atomic nuclei?
What is the definition of the atomic mass number (A)?
Write a mathematical expression
that relates mass number (A) to atomic number (Z) and the
number of neutrons (n^{0}).
What is the meaning of the
number that often follows the name of an element?
When the name of an element is followed by a number
(as in calcium-40), what does it refer to, an isotope or
an element? Why?
Review
What is alpha decay?
What is the atomic symbol for an
alpha-particle?
What is beta decay?
What is the atomic symbol for a
beta-particle?
What is positron decay?
What is the atomic symbol for a positron?
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What is electron-capture decay?
What is the atomic symbol for an
electron?
Nuclear Decay Equations
Nuclear equations are used communicate about natural
radioactive decay and other nuclear events such as fission,
fusion, and transmutation. All nuclear equations follow a
simple pair of rules. First, the sum of all atomic numbers
on one side of the equation must equal the sum of all
atomic numbers on the other side of the equation. Second,
the sum of all mass numbers on one side of the equation
must equal the sum of all mass numbers on the other side of
the equation. Model 2 shows some example nuclear decay
equations.
1. ^{208}_{84}Po
—> ^{4}_{ 2}He
+ ^{204}_{82}Pb
2. ^{14}_{ 6}C
—> ^{14}_{ 7}N
+ ^{0}_{-1}β^{–}
3. ^{50}_{25}Mn
—> ^{50}_{24}Cr
+ ^{0}_{+1}β^{+}
4. ^{81}_{36}Kr
+ ^{0}_{-1}e^{–}
—> ^{81}_{35}Br
Model 2
What does the arrow mean in
these equations?
Describe what is happening in
nuclear equation number one, at left.
What is happening in equation
number 2?
What is happening in equation
number 3?
What is happening in equation
number 4?
Write a nuclear equation for the
alpha decay of americium-243.
Write a nuclear equation for the
beta decay of oxygen-19.
Write a nuclear equation for the
positron decay of bromine-68.
Write a nuclear equation for the
electron capture decay of nickel-56.
Given the decay mode and a
daughter nucleus, how would you figure out the identity
of the parent nucleus?
Write a balanced nuclear equation for an
alpha decay that produces radon-218 as the daughter.
Write a balanced nuclear equation for a
beta decay that produces xenon-131 as the daughter.
Write a balanced nuclear equation for a
positron decay that produces chromium-50 as the daughter.
Write a balanced nuclear equation for an
electron capture decay that produces uranium-233 as the
daughter.
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Other Nuclear Equations
Nuclear equations can also be used to describe other
interesting things besides nuclear decay. For example, all
life on Earth owes its existence to atomic fusion reactions
happening deep in the core of the Sun. Fusion is when atomic
nuclei smash into one another and combine along with the
release of an enormous amount of energy. Nuclear electric
power stations and nuclear bombs both operate by taking
advantage of the process of atomic fission. Atomic fission
is when an atom breaks apart into two large nuclear pieces.
Finally, transmutation is when atomic nuclei are smashed
together to form new nuclei. Lead cannot be made into gold
this way but it is possible to change small numbers of
atoms of one element into another. Model 3 shows several
illustrations of these processes along with the nuclear
equations which describe them.
Describe what happened in the
fission illustration above.
What is the meaning of the
coefficient in front of the symbol for a neutron?
Check the sums of atomic and
mass numbers in the fission equation. Do they work
out as equal on both sides?
What makes a fusion reaction
different from a fission reaction?
Describe what happened in the
transmutation illustration above.
Check the sums of atomic and
mass numbers in the transmutation equation. Do they work out as
equal on both sides?
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Complete the following exercises to practice writing and
completing nuclear decay, fusion, fission, and
transmutation equations.
For the following exercises, fill in the missing particle
and give a name to what is happening. Identify whether it
is a type of nuclear decay, fission, fusion, or
transmutation. Only one particle is missing from each
equation. Space has been provided both before and after the
arrow but you must determine where the missing particles
belong.
^{234}_{90}Th
—> ^{4}_{2}He
^{201}_{79}Au
—> ^{0}_{–1}e^{–}
^{47}_{27}Co
—> ^{47}_{26}Fe
(there are two possible correct answers; give both)
Each of the following exercises describes a nuclear change. Write a correct and balanced nuclear equation for each one.
A neptunium-237 nucleus undergoes alpha-decay.
Write an equation for the positron decay of gallium-59.
An iron-58 nucleus is hit by a bismuth-209 nucleus to form meitnerium-266 and a neutron.
Write an equation for the electron capture decay of polonium-200.
A plutonium-239 nucleus absorbs a neutron and fissions to release three neutrons, a krypton-81 nucleus and one other atomic nucleus.
Magnesium-24 is the result of the beta-decay of another isotope of another element. Identify the element and write the nuclear equation.
On a separate piece of paper create an outline that
contains all of the main points that you believe you were
meant to learn by doing this activity. Do it with bullets
or with headings and sub-headings (A., B., 1., 2., etc.)
Work with your group on this part and consult with your
teacher before moving on to the next part of the
activity.
On a separate piece of paper use your outline to
write a short paragraph that summarizes all of the main
points you wrote above. Do this part completely
independently but share your work with your group members
after you are finished. Make any changes or additions you
find necessary to make a final draft of this information.
Type up this draft to turn in as the recorder’s report.