Do Now
• Write a balanced nuclear equation for the
alpha decay that produces uranium-238.
𝟐𝟒𝟐
Pu
𝟗𝟒

𝟐𝟑𝟖
𝟒
U + He
𝟗𝟐
𝟐
slide 1
Do Now
Solve for x
𝟏 3
1) x = ( )
𝟐
2) x = 𝟏𝟔
𝟑
𝟒
x =
𝟏
𝟖
x = 8
3) 𝟎. 𝟓𝐱 = 0.125
x = 3
4) 𝟎. 𝟓𝟔𝐱 = 0.0625
x = 0.667
slide 2
Announcement
• Test #4 - Wed, Dec 10 (tentative)
• Nuclear Chemistry
–
–
–
–
–
–
–
–
–
–
The concept of radioactivity
Chemical vs nuclear reactions
Major types of radioactivity
Factors that determine nuclear stability
Band of stability
Predicting nuclear decay pathways
Writing and balancing nuclear equations
Nuclear binding energy & mass defect
Fission and fusion
Half-life and kinetics of decay
slide 3
Nuclear Reactions
Write this in
your notes
SWBAT explain the concepts of nuclear fission
and fusion, predict which will happen based
upon nuclear binding energy, and write
balanced equations for each.
2-day lesson
slide 4
Review
Nuclear reactions
• A reaction that involves a change to an
atom's nucleus.
• Can produce enormous amounts of energy
slide 5
Two Types of Nuclear Reactions
Nuclear fission - a nucleus splitting into two or more parts
Nuclear fusion - two nuclei joining together into one
Write this in
your notes
slide 6
What determines if a nucleus will
undergo fission or fusion?
• A nucleus will undergo whichever
process makes it more stable
• So how do we know the relative
stability of different nuclei?
slide 7
How do we measure
stability of a nucleus?
The amount of energy
required is directly
related to the stability
of the nucleus
+
++
+
+
+
+
+
+
+
component
parts
ΔErequired
nucleus
slide 8
Nuclear Binding Energy
• Nuclear binding energy is the energy required
to split the nucleus of an atom into its
component parts (e.g protons and neutrons)
Write this in your notes
• Explaining nuclear binding energy requires a
complex discussion of Einstein's theory of
mass-energy equivalence.
• You will only be responsible for explaining
the concept of mass defect and its use in
deriving nuclear binding energy
slide 9
How do we measure this energy?
 Separating a nucleus into
its component parts is not
easy to do.
 It requires huge amounts
of energy.
 It is hard to measure.
slide 10
But how to measure this energy?
 But there is another way
 We can measure this
energy indirectly by
measuring the mass
difference
 And using E = mc2
slide 11
Measure the mass difference
Mass difference? What mass difference?
+
++
+
nucleus
+
+
+
+
+
+
component
parts
Shouldn't the mass of the nucleus should
be the sum of the component parts?
slide 12
Measure the mass difference
+
+
+
+
+
+
+
++
+
nucleus
component
parts
12.00000 u
12.09564 u
Difference is 0.09564 u
slide 13
Mass-Energy Equivalence
• Mass and energy have a direct relationship as
establish by Einstein's famous equation
• 𝑬 = 𝒎𝒄𝟐
•
E = energy, m = mass, c = speed of light (670,000,000 mph)
• Normally we don't notice this relationship
because even large change in energy results in
a very small change in mass
•
Δ𝑬
𝒄𝟐
=
Δ𝑬
𝒂 𝒗𝒆𝒓𝒚 𝒃𝒊𝒈 𝒏𝒖𝒎𝒃𝒆𝒓
= Δm
• For example:
• 90,000,000 J of energy changes mass by 0.000001 g
slide 14
Life is different in the nucleus
• Strong nuclear force is the most powerful force
in the universe
• Because of strong nuclear force, a HUGE
amount of energy is required to split the nucleus
into its component parts
• With amounts of energy this large, the massenergy equivalence is detectable.
slide 15
But how to measure this energy?
 When this huge amount
of energy is added to the
system, the mass goes
up.
 How much?
slide 16
Measure the mass difference
+
+
+
+
+
+
+
++
+
nucleus
This much!!!
12.00000 u
component
parts
12.09564 u
Difference is 0.09564 u
The difference between these two is called the mass defect
slide 17
Mass Defect
• Mass defect is the difference between the mass
of a nucleus and the mass of its component
parts
Write this in your notes
• By measuring the mass defect, the nuclear
binding energy can be determined
– An example of this calculation is shown on pg 878 in your book
• Nuclear binding energy provides an estimate of
relative stability of different nuclei
• High nuclear binding energy - high stability
• Low nuclear binding energy - low stability
Write this in your notes
slide 18
Last Class
slide 19
Iron is the most stable
element, with the highest
binding energy.
This is why iron is such an
abundant element
Sketch this
graph in your
notes
slide 20
Fission
Process where a nuclei splits apart
Fission reactions
Fission reactions
The daughters are more
stable than the parents so
energy is released
slide 21
Fusion
Process where two nuclei join together
Fusion reactions
Fission reactions
Fusion
ReactionsThe daughters are more
stable than the parents so
energy is released
slide 22
What determines if a nucleus will
undergo fission or fusion?
• A nucleus will undergo whichever
process makes it more stable
• Nuclear binding energy measures the
relative stability of different nuclei
• The optimum mass is around A=60
− Mass number >60, fission is favored
− Mass number <60, fusion is favored
Write this in your notes!!!
slide 23
Fission Reactions
Nuclear fission - a nuclei splitting into two or more parts
slide 24
Do Now
• Write a balanced nuclear equation for the
alpha decay that produces uranium-238.
𝟐𝟒𝟐
Pu
𝟗𝟒

𝟐𝟑𝟖
𝟒
U + He
𝟗𝟐
𝟐
slide 25
Previous Classes
slide 26
Transmutation & Fissionable
• Fission always involves transmutation
• Transmutation is the conversion of one atom of
an element to an atom of another element
• Sometimes this occurs spontaneously
– e.g. radioactive decay
• Sometimes this is forced to occur
Write this
in your
notes
– e.g. caused by bombardment with particles
– Called "induced transmutation"
• Fissionable - material capable of undergoing
fission upon bombardment
slide 27
Fission of Uranium-235
When uranium-235 is bombarded with neutrons, it
can breaks apart (fissions) according to the equation:
n
1
0
U
235
92
99
42
Mo 
Sn  2 01n  energy
135
50
Fission products
Write this in your notes
slide 28
U-236
slide 29
Fission of Uranium-235
When uranium-235 is bombarded with neutrons, it
can breaks apart (fissions) according to the equation:
n
1
0
U
235
92
99
42
Mo 
Sn  2 01n  energy
135
50
Fission products
slide 30
Fission Converts U-235
into More Stable Nuclei
Fission reactions
Fission reactions
Notice that the nuclei of Mo and Sn
have greater binding energy and
therefore are more stable than U
slide 31
Writing Balanced Nuclear Equations
𝟏
n + 𝟐𝟑𝟓U
𝟎
𝟗𝟐

𝟗𝟗
Mo + 𝟏𝟑𝟓Sn + 2 𝟏n
𝟎
𝟒𝟐
𝟓𝟎
slide 32
Balanced the Mass Numbers
Mass Number
1 + 235 = 236
𝟏
n + 𝟐𝟑𝟓U
𝟎
𝟗𝟐
Mass Number
99 + 135 + (2 x 1) = 236

𝟗𝟗
Mo + 𝟏𝟑𝟓Sn + 2 𝟏n
𝟎
𝟒𝟐
𝟓𝟎
slide 33
Balanced the Atomic Numbers
Mass Number
1 + 235 = 236
𝟏
n + 𝟐𝟑𝟓U
𝟎
𝟗𝟐
Atomic Number
0 + 92 = 92
Mass Number
99 + 135 + (2 x 1) = 236

𝟗𝟗
Mo + 𝟏𝟑𝟓Sn + 2 𝟏n
𝟎
𝟒𝟐
𝟓𝟎
Atomic Number
42 + 50 + (2 x 0) = 92
slide 34
Independent Practice 1
• The fission of uranium-235 by a neutron can
produce many fission products. For the case where
it produces krypton-91 (Kr) and barium-142 (Ba),
write the nuclear equation and determine how many
neutrons are produced.
slide 35
Independent Practice 1
• The fission of uranium-235 by a neutron can
produce many fission products. For the case where
it produces krypton-91 (Kr) and barium-142 (Ba),
write the nuclear equation and determine how many
neutrons are produced.
𝟏
𝟐𝟑𝟓
n +
U
𝟎
𝟗𝟐

𝟗𝟏
𝟏𝟒𝟐
𝟏
Kr +
Ba + 3 n
𝟑𝟔
𝟓𝟔
𝟎
slide 36
Independent Practice 2
• The fission of uranium-235 by a neutron can
produce many fission products. For the case where
it produces yttrium-97 (Y), five neutrons and another
fission product, write the nuclear equation and
determine how what other fission product is made.
slide 37
Independent Practice 2
• The fission of uranium-235 by a neutron can
produce many fission products. For the case where
it produces yttrium-97 (Y), five neutrons and another
fission product, write the nuclear equation and
determine how what other fission product is made.
𝟏
𝟐𝟑𝟓
n +
U
𝟎
𝟗𝟐

𝟗𝟕
𝟏𝟑𝟒
𝟏
𝐘 +
I+ 5 n
𝟑𝟗
𝟓𝟑
𝟎
slide 38
Independent Practice 3
• The fission of plutonium-240 (Pu) by a neutron can
produce many fission products. For the case where
it produces lanthanum-137 (La) and rubidium-94
(Rb), write the nuclear equation and determine how
many neutrons are produced.
slide 39
Independent Practice 3
• The fission of plutonium-240 (Pu) by a neutron can
produce many fission products. For the case where
it produces lanthanum-137 (La) and rubidium-94
(Rb), write the nuclear equation and determine how
many neutrons are produced.
𝟏
𝟐𝟒𝟎
n +
Pu
𝟎
𝟗𝟒

𝟏𝟑𝟕
𝟗𝟒
𝟏
La +
Rb + 10 n
𝟓𝟕
𝟑𝟕
𝟎
slide 40
What is all the arguing about???
SERIOUSLY?!?
All this arguing over
a simple isotope,
uranium-235?
Benjamin Netanyahu
Mahmoud Ahmadinejad
slide 41
What makes U-235 so special?
• U-235 is a naturally-occurring isotope
• Typical uranium ore contains:
>99% U-238 & <1% U-235
• Uranium ore can become "enriched" in U-235
through a complex and difficult process
• 5-20% enriched uranium is needed for
nuclear power
• >85% enriched uranium is needed for nuclear
weapons
slide 42
Key Points
Write this
in your
notes
• U-235 is a naturally-occurring isotope capable of
starting and propagating a nuclear chain reaction.
slide 43
What is a Nuclear Chain Reaction?
• A nuclear chain reaction is a self-sustaining
sequence of nuclear fission reactions.
• One atom undergoes fission
• This triggers another atom to undergo fission
• Which triggers another atom to undergo fission . . .
• The sequence, once started, continues with no external
triggers
slide 44
Key Points
Write this
in your
notes
• U-235 is a naturally-occurring isotope capable of
starting and propagating a nuclear chain reaction.
• A nuclear chain reaction is a self-sustaining
sequence of nuclear fission reactions.
slide 45
How does U-235 start & propagate
a nuclear chain reaction?
n
1
0
U
235
92
1 neutron,
1 fission
99
42
Mo 
Sn  2 01n  energy
135
50
Fission
products
slide 46
n
1
0
U
235
92
99
42
Mo 
Sn  2 01n  energy
135
50
1 neutron,
1 fission
Can these 2 neutrons
cause 2 other fissions?
slide 47
1 neutron,
1 fission
Can these 2 neutrons
cause 2 other fissions?
Yes!
slide 48
2 neutrons,
2 fissions
1 neutron,
1 fission
Fission
products
slide 49
2 neutrons,
2 fissions
4 neutrons,
4 fissions
1 neutron,
1 fission
Each neutron then causes one
more fission reaction
slide 50
How does U-235 start & propagate
a nuclear chain reaction?
2 neutrons,
2 fissions
4 neutrons,
4 fissions
1 neutron,
1 fission
Each neutron then causes one
more fission reaction
Because its fission creates
more neutrons than it consumes!
slide 51
Fissile Material for Chain Reactions
• A material capable of sustaining a nuclear fission
chain reaction with neutrons of any energy
• Fissile rule
 90 ≤ Z ≤ 100
 2Z - N = 43 ± 2
• Different from a fissionable materials. All fissile materials are
fissionable materials but not the other way around. Materials
that require high energy neutrons are not considered fissileslide 52
Key Points
Write this
in your
notes
• U-235 is a naturally-occurring isotope capable of
starting and propagating a nuclear chain reaction.
• A nuclear chain reaction is a self-sustaining
sequence of nuclear fission reactions.
• U-235 can do this because its fission creates more
neutrons than it consumes.
slide 53
Critical Mass
• Critical mass is another key factor to consider
• For a chain reaction to occur, there has to be
enough fissionable atoms around to collide with
released neutrons and propagate the chain.
• Not enough - subcritical mass
• Just enough - critical mass
• More than enough - supercritical mass
• Critical mass is the minimum amount of fissionable
material necessary to sustain a nuclear chain
reaction
slide 54
slide 55
Key Points
Write this
in your
notes
• U-235 is a naturally-occurring isotope capable of
starting and propagating a nuclear chain reaction.
• A nuclear chain reaction is a self-sustaining
sequence of nuclear fission reactions.
• U-235 can do this because its fission creates more
neutrons than it consumes.
• Enough U-235 is needed to achieve critical mass,
the minimum amount of fissionable material
necessary to sustain a nuclear chain reaction
slide 56
So where
do we
stand?
Hassan Rouhani
Ali Hosseini
Khamenei
slide 57
Fusion Reactions
Nuclear fusion - two nuclei joining together into one
slide 58
Fusion
Process where two nuclei join together
Fusion reactions
Fission reactions
Fusion
reactions
The products are more stable than
The
daughters
are more
the
starting
material
so:
than theproceeds
parents so
•stable
the reaction
forward
energy
released
• energy
is is
released
slide 59
Fusion
• Fusion is less familiar to most people
• Fusion is more difficult to initiate and sustain
than fission
• The stars use fusion to generate energy
slide 60
Fusion Energy is Very Attractive
• Fuels are cheap and abundant
– Reaction can hydrogen gas or other abundant elements
• Little radioactive waste
• Reactors can't get out of control
– Fusion would just stop
• Large projects are trying to achieve fusion
– Seeking to produce more energy than required to start
the reaction
slide 61
Fusion of Carbon & Hydrogen
𝟏𝟐
𝟔𝑪
+
𝟏
𝟏𝑯
𝟏𝟑
𝟔𝑪
+
𝟎
+𝟏𝒆
slide 62
Balance the Mass Number
Mass Number
12 + 1 = 13
𝟏𝟐
𝟔𝑪
+
𝟏
𝟏𝑯
Mass Number
13 + 0 = 13
𝟏𝟑
𝟔𝑪
+
𝟎
+𝟏𝒆
slide 63
Balance the Atomic Number
Mass Number
12 + 1 = 13
𝟏𝟐
𝟔𝑪
+
𝟏
𝟏𝑯
Atomic Number
6+1=7
Mass Number
13 + 0 = 13
𝟏𝟑
𝟔𝑪
+
𝟎
+𝟏𝒆
Atomic Number
6+1=7
slide 64
Equation is Balanced
Mass Number
12 + 1 = 13
𝟏𝟐
𝟔𝑪
+
𝟏
𝟏𝑯
Atomic Number
6+1=7
Mass Number
13 + 0 = 13
𝟏𝟑
𝟔𝑪
+
𝟎
+𝟏𝒆
Atomic Number
6+1=7
slide 65
Solve This Problem
Two helium-3 atoms fuse together to form one helium-4 atom and
some hydrogen-1. Write a balanced equations and determine how
many atoms of hydrogen-1 are produced.
slide 66
Write the Reactants
Two helium-3 atoms fuse together to form one helium-4 atom and
some hydrogen-1. Write a balanced equations and determine how
many atoms of hydrogen-1 are produced.
helium-3 =
𝟑
𝟐𝑯𝒆
helium-4 =
𝟒
𝟐𝑯𝒆
hydrogen-1 =
𝟏
𝟏𝑯
slide 67
Write the Equation
Two helium-3 atoms fuse together to form one helium-4 atom and
some hydrogen-1. Write a balanced equations and determine how
many atoms of hydrogen-1 are produced.
2
𝟑
𝟐𝑯𝒆
𝟒
𝟐𝑯𝒆
+ ?
𝟏
𝟏𝑯
slide 68
Balance the Mass Number
Two helium-3 atoms fuse together to form one helium-4 atom and
some hydrogen-1. Write a balanced equations and determine how
many atoms of hydrogen-1 are produced.
Mass Number
(2 x 3) = 6
2
𝟑
𝟐𝑯𝒆
Mass Number
4 + (2 x 1) = 6
𝟒
𝟐𝑯𝒆
+ 2
𝟏
𝟏𝑯
slide 69
Balance the Atomic Number
Two helium-3 atoms fuse together to form one helium-4 atom and
some hydrogen-1. Write a balanced equations and determine how
many atoms of hydrogen-1 are produced.
Mass Number
(2 x 3) = 6
2
𝟑
𝟐𝑯𝒆
Atomic Number
(2 x 2) = 4
Mass Number
4 + (2 x 1) = 6
𝟒
𝟐𝑯𝒆
+ 2
𝟏
𝟏𝑯
Atomic Number
2 + (2 x 1) = 4
slide 70
Balanced Equation
Two helium-3 atoms fuse together to form one helium-4 atom and
some hydrogen-1. Write a balanced equations and determine how
many atoms of hydrogen-1 are produced.
2
𝟑
𝟐𝑯𝒆
𝟒
𝟐𝑯𝒆
+ 2
𝟏
𝟏𝑯
Two atoms of hydrogen-1 are produced.
slide 71
Independent Practice 4
• The fusion of uranium-238 and nitrogen-14
produces a fusion product and four neutrons. Write
a balanced nuclear equation that describes this
fusion reaction.
𝟐𝟑𝟖
𝟏𝟒
U + N
𝟗𝟐
𝟕

𝟐𝟒𝟖
𝟏
Es + 4 n
𝟗𝟗
𝟎
slide 72
Independent Practice 5
• An unknown nuclide fuses with helium-4 to produce
oxygen-16 and a neutron. Write a balanced nuclear
equation that describes this fusion reaction.
𝟏𝟑
𝟒
C + He
𝟔
𝟐

𝟏𝟔
𝟏
O+ n
𝟖
𝟎
slide 73
Independent Practice 6
• Lawrencium-257 and six neutrons were produced
through the fusion of californium-252 and another
nuclide. Write a balanced nuclear equation that
describes this fusion reaction.
𝟏𝟏
𝟐𝟓𝟐
Cf + B
𝟓
𝟗𝟖

𝟏
𝟐𝟓𝟕
Lr + 6 n
𝟎
𝟏𝟎𝟑
slide 74
Worksheet
• Start in class
• Finish for homework
• Be sure to ask for help if you need it
slide 75
Good video on mass defect
https://www.youtube.com/watch?v=4HgvPBAOea8
slide 76
Decay versus Fission
• By definition, most decay qualifies as a form of fission
• In common usage, however, the meanings are different
• Radioactive decay is a spontaneous process where the
nucleus tries to get into the band of stability. The
fragment lost is usually no bigger than a-particles
• In common usage, fission is an induced transmutation.
It leads to the transient production of an unstable
nucleus which undergoes fission. The fragments are
usually larger than a-particles
slide 77