Post on 17-Jan-2018
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slide 1
Do NowWhat would be the product if radon-222 underwent decay to produce
1) an alpha particle polonium-218
2) a beta particle francium-222
3) a gamma particle radon-222
4) a positron emission astatine-222
slide 2
Impact of Decay
type atomic notation DNp DNn DZ DA
alpha ‒2 ‒2 ‒2 ‒4
beta +1 ‒1 +1 0
gamma 0 0 0 0
positron ‒1 +1 ‒1 0
slide 3
Do NowWhat would be the product if radon-222 underwent decay to produce
1) an alpha particle polonium-218
2) a beta particle francium-222
3) a gamma particle radon-222
4) a positron emission astatine-222
slide 4
Do NowWhat would be the product if radon-222 underwent decay to produce
1) an alpha particle polonium-218
2) a beta particle francium-222
3) a gamma particle radon-222
4) a positron emission astatine-222
slide 5
Do NowWhat would be the product if radon-222 underwent decay to produce
1) an alpha particle polonium-218
2) a beta particle francium-222
3) a gamma particle radon-222
4) a positron emission astatine-222
slide 6
Do NowWhat would be the product if radon-222 underwent decay to produce
1) an alpha particle polonium-218
2) a beta particle francium-222
3) a gamma particle radon-222
4) a positron emission astatine-222
slide 7
Do NowWhat would be the product if radon-222 underwent decay to produce
1) an alpha particle polonium-218
2) a beta particle francium-222
3) a gamma particle radon-222
4) a positron emission astatine-222
slide 8
Nuclear Stability
SWBAT explain the factors that influence nuclear stability, the characteristics of the band of stability, and predict the radioactive decay path of a nuclei based on these principles
Write this in your notes
slide 9
Why Are Some Nuclei Radioactive?• Some nuclei are radioactive• Some nuclei are stable• What factors determine this difference?
slide 10
Factors in Nuclear Stability
1) (n/p) ratio
2) odd or even Np and Nn
3) atomic number
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slide 11
How does a nucleus stay together?
Note:1) A nucleus has multiple protons all very
close to each other2) Protons are positively charged3) Like charges repel each other
Why doesn't the nucleus blow apart?
Strong Nuclear Force
slide 12
Strong Nuclear Force• A force that acts on subatomic particles
that are extremely close together• The strongest of the four fundamental
forces of the universe
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slide 13
Forces in the NucleusAttraction
The strong nuclear force attracts protons to protons, neutrons to
neutrons, and protons to neutrons
Repulsion
The electromagnetic force cause like charges to repel each other
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The stability of the nucleus partially depends on the balance between attractive strong nuclear force and repulsive electromagnetic force.
slide 14
1) Neutron to Proton Ratio• A key factor in the stability of a nuclei is the
neutron to proton ratio - the (n/p) ratio• Each proton contributes to both repulsion
and attraction in the nucleus• Each neutron contributes to attraction only
• At low mass numbers, a 1.0 (n/p) ratio seems optimum for stability
• As the mass number rises, the optimum (n/p) ratio rises to 1.5
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slide 15
Graph Np on x-axis
Graph Nn on y-axis
A black point represents every stable nuclei
All points lay between lines with slopes of 1.0 and 1.5
This collection of stable nuclei is known as the
BAND OF STABILITYWrite this in your notes
slide 16
2) Odd and Even Np and Nn
• Having an even number of either protons or neutrons or both confers stability
• Stability believed to be derived from pairing of spin numbers
number of stable nuclei Np Nn %
148 even even 58%53 even odd
40%48 odd even5 odd odd 2%
Total: 254
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slide 17
The Stability Associated with Even Np & Nn
Creates Zig-Zag Shape
slide 18
3) Atomic Number
All elements with atomic numbers greater than 83 are unstable and undergo spontaneous
radioactive decay
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slide 19
slide 20
What does an unstable nuclei do?• If a nuclei is unstable, it will undergo
radioactive decay to make it more stable
• Each unstable nuclei will decay in a way that will address the source of instability
If Z is too high
slide 21
What does an unstable nuclei do?• If a nuclei is unstable, it will undergo
radioactive decay to make it more stable
• Each unstable nuclei will decay in a way that will address the source of instability
If Z is too high Æ lower Z
slide 22
What does an unstable nuclei do?• If a nuclei is unstable, it will undergo
radioactive decay to make it more stable
• Each unstable nuclei will decay in a way that will address the source of instability
If Z is too high Æ lower Z
If (n/p) is too high
slide 23
What does an unstable nuclei do?• If a nuclei is unstable, it will undergo
radioactive decay to make it more stable
• Each unstable nuclei will decay in a way that will address the source of instability
If Z is too high Æ lower Z
If (n/p) is too high Æ lower (n/p)
slide 24
What does an unstable nuclei do?• If a nuclei is unstable, it will undergo
radioactive decay to make it more stable
• Each unstable nuclei will decay in a way that will address the source of instability
If Z is too high Æ lower Z
If (n/p) is too high Æ lower (n/p)
If (n/p) is too low
slide 25
What does an unstable nuclei do?• If a nuclei is unstable, it will undergo
radioactive decay to make it more stable
• Each unstable nuclei will decay in a way that will address the source of instability
If Z is too high Æ lower Z
If (n/p) is too high Æ lower (n/p)
If (n/p) is too low Æ raise (n/p)
slide 26
Pathways to Nuclear Stability
type process Δp Δn impact when utilized
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slide 27
Pathways to Nuclear Stability
type process Δp Δn impact when utilized
a decay à ‒2 ‒2 Z falls Z > 83
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slide 28
Pathways to Nuclear Stability
type process Δp Δn impact when utilized
a decay à ‒2 ‒2 Z falls Z > 83
b decay n à p + e‒ +1 ‒1 n/p falls high n/p
Write this in your notes
slide 29
Pathways to Nuclear Stability
type process Δp Δn impact when utilized
a decay à ‒2 ‒2 Z falls Z > 83
b decay n à p + e‒ +1 ‒1 n/p falls high n/p
positron emission p à n + e+ ‒1 +1 n/p rises low n/p
electron capture p + e‒ à n ‒1 +1 n/p rises low n/p
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slide 30
Electron Capture Write this in your notes
neutronproton electron
▬
• Electron capture is a nuclear process to improve nuclear stability
• A proton from the nucleus "captures" an electron from the electron cloud.
• Together they become a neutron which remains in the nucleus.
• Nuclear impact is same as positron emission• Opposite process from beta decay
• Not radioactive decay because no radiation is released
slide 31
Day 2 Intro
slide 32
Do Now
Po ª Pb ª Bi ª Tl
Some unstable isotopes need to undergo a series of radioactive decays to reach a stable isotope. These are called "decay chains". For example, polonium-213 suffers a-decay, then b-decay, and then another a decay to reach a stable isotope. Determine the products of each step of this decay chain.
slide 33
slide 34
Impact of Decay
type atomic notation DNp DNn DZ DA
alpha ‒2 ‒2 ‒2 ‒4
beta +1 ‒1 +1 0
gamma 0 0 0 0
positron ‒1 +1 ‒1 0
REVIEW
slide 35
Forces in the NucleusAttraction
The strong nuclear force attracts protons to protons, neutrons to
neutrons, and protons to neutrons
Repulsion
The electromagnetic force cause like charges to repel each other
The stability of the nucleus partially depends on the balance between attractive strong nuclear force and repulsive electromagnetic force.
REVIEW
slide 36
Factors in Nuclear Stability
1) (n/p) ratio
2) odd or even Np and Nn
3) atomic number
REVIEW
slide 37
Graph Np on x-axis
Graph Nn on y-axis
A black point represents every stable nuclei
All points lay between lines with slopes of 1.0 and 1.5
This collection of stable nuclei is known as the
BAND OF STABILITY
REVIEW
slide 38
2) Odd and Even Np and Nn
• Having an even number of either protons or neutrons or both confers stability
• Stability believed to be derived from pairing of spin numbers
number of stable nuclei Np Nn
148 even even53 even odd48 odd even5 odd odd
REVIEW
slide 39
REVIEW
slide 40
What does an unstable nuclei do?• If a nuclei is unstable, it will undergo
radioactive decay to make it more stable
• Each unstable nuclei will decay in a way that will address the source of instability
If Z is too high Æ lower Z
If (n/p) is too high Æ lower (n/p)
If (n/p) is too low Æ raise (n/p)
REVIEW
slide 41
Pathways to Nuclear Stability
type process Δp Δn impact when utilized
a decay à ‒2 ‒2 Z falls Z > 83
b decay n à p + e‒ +1 ‒1 n/p falls high n/p
positron emission p à n + e+ ‒1 +1 n/p rises low n/p
electron capture p + e‒ à n ‒1 +1 n/p rises low n/p
REVIEW
How Accurate Are These Predictions?
slide 42
Graphic Analysis of Predictions• The band of stability is
the red line.
slide 43
Too Many Neutrons• Any atom above the
red line will have a high n/p ratio
• These will be unstable and undergo a nuclear reaction to lower the n/p ratio
• Thus, any atom above the line should undergo beta decay
b decay
slide 44
Too Many Protons• Any atom below the
red line will have a low n/p ratio
• These will be unstable and undergo a nuclear reaction to raise the n/p ratio
• Thus, any atom above the line should undergo positron emission or electron capture
b+ or e–
capture
slide 45
Z is Too High• Any atom with Z > 83
will have a Z value that is too high
• These will be unstable and undergo a nuclear reaction to lower Z
• Thus, any atom with Z > 83 should undergo alpha decay.
adecay
slide 46
Predicted Decay Trends on Graph
adecay
b+ or e–
capture
b decay
slide 47
Predicted Observed
slide 48
Predicted Decay Trends on Graph
adecay
b+ or e–
capture
b decay
Draw this in your notes
slide 49
Check For Understanding 1
Predict the decay pathway of hydrogen-3
1) Z = Np = 1
2) A = 3, Nn = A - Np = 2
3) n/p = 2.0 (too high)
4) Need to lower n/p, so b-decay
5) helium-3Write this in your notes
slide 50
Check For Understanding 2
Predict the decay pathway of plutonium-244
1) Z = Np = 94, Z > 83
2) Need to lower Z, so a-decay3) uranium-2404) or, n/p = 150/94 = 1.59 (too high)5) need to lower n/p, so b-decay6) americium-244
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slide 51
Check For Understanding 3
Predict the decay pathway of nitrogen-13
1) Z = Np = 7
2) A = 13, Nn = A - Np = 6
3) n/p = 0.86 (too low), need to raise n/p
4) positron emission or electron capture
5) carbon-13Write this in your notes
slide 52
Pathways to Nuclear Stability
type process Δp Δn impact when utilized
a decay à ‒2 ‒2 Z falls Z > 83
b decay n à p + e‒ +1 ‒1 n/p falls high n/p
positron emission p à n + e+ ‒1 +1 n/p rises low n/p
electron capture p + e‒ à n ‒1 +1 n/p rises low n/p
slide 53
Independent Practice
Predict the radioactive decay pathway1) carbon-14
n/p = 1.3 (too high), reduce n, b-decay
2) radon-222 Z = 86 (Z>83), reduce p, a-decay
3) magnesium-22 n/p = 0.83 (too low), reduce p, positron emission
4) lead-214 n/p = 1.6 (too high), reduce n, b-decay
slide 54
Independent Practice
Predict the radioactive decay pathway1) carbon-14
n/p = 1.3 (too high), reduce n/p, b-decay
2) radon-222 Z = 86 (Z>83), reduce Z, a-decay, polonium-218 or n/p = 1.58 (too high), reduce n/p, b-decay, franconium-222
3) magnesium-22 n/p = 0.83 (too low), raise n/p, positron emission, sodium-22
4) lead-214 n/p = 1.6 (too high), reduce n/p, b-decay, bismuth-214
slide 55
Independent Practice
Predict the radioactive decay pathway1) carbon-14
n/p = 1.3 (too high), reduce n/p, b-decay
2) radon-222 Z = 86 (Z>83), reduce Z, a-decay, polonium-218 or n/p = 1.58 (too high), reduce n/p, b-decay, franconium-222
3) magnesium-22 n/p = 0.83 (too low), raise n/p, positron emission, sodium-22
4) lead-214 n/p = 1.6 (too high), reduce n/p, b-decay, bismuth-214
slide 56
Independent Practice
Predict the radioactive decay pathway1) carbon-14
n/p = 1.3 (too high), reduce n/p, b-decay
2) radon-222 Z = 86 (Z>83), reduce Z, a-decay, polonium-218 or n/p = 1.58 (too high), reduce n/p, b-decay, franconium-222
3) magnesium-22 n/p = 0.83 (too low), raise n/p, positron emission, sodium-22
4) lead-214 n/p = 1.6 (too high), reduce n/p, b-decay, bismuth-214
slide 57
Independent Practice
Predict the radioactive decay pathway1) carbon-14
n/p = 1.3 (too high), reduce n/p, b-decay
2) radon-222 Z = 86 (Z>83), reduce Z, a-decay, polonium-218 or n/p = 1.58 (too high), reduce n/p, b-decay, franconium-222
3) magnesium-22 n/p = 0.83 (too low), raise n/p, positron emission, sodium-22
4) lead-214 n/p = 1.6 (too high), reduce n/p, b-decay, bismuth-214
slide 58
Day 3 Intro
slide 59
Do Now• What are the primary forces acting on the
nucleus? How do they impact the particles in the nucleus and nuclear stability?
• What are the three factors used to estimate nuclear stability? What are the optimum values for these three factors?
slide 60
Particle Review 1• Below are two nuclear processes.
A. How would each one change a nucleus? B. What is the name of each process? C. Under what circumstances would a nucleus want to
undergo each process?
–
+
–
+
proton
neutron
electron
positron
slide 61
Particle Review 2
–
–
+
proton
neutron
electron
positron
• Below are two nuclear processes. A. How would each one change a nucleus? B. What is the name of each process? C. Under what circumstances would a nucleus want to
undergo each process?
slide 62
Analysis of Nuclear StabilityFluorine-16 is radioactive.1) Analyze all 3 factors of stability & determine which
need to be changed2) Predict decay pathway and product3) Reanalyzed the 3 factors of stability to determine if
they are now acceptable
slide 63
Analysis of Nuclear StabilityFluorine-16 is radioactive.1) Analyze all 3 factors of stability & determine which
need to be changed2) Predict decay pathway and product3) Reanalyzed the 3 factors of stability to determine if
they are now acceptable
too low LNp: oddNn: odd LZ < 83 J
F ª O + e
slide 64
Analysis of Nuclear StabilityFluorine-16 is radioactive.1) Analyze all 3 factors of stability & determine which
need to be changed2) Predict decay pathway and product3) Reanalyzed the 3 factors of stability to determine if
they are now acceptable
too low LNp: oddNn: odd LZ < 83 J
F ª O + eb+
slide 65
Analysis of Nuclear StabilityFluorine-16 is radioactive.1) Analyze all 3 factors of stability & determine which
need to be changed2) Predict decay pathway and product3) Reanalyzed the 3 factors of stability to determine if
they are now acceptable
too low LNp: oddNn: odd LZ < 83 J
JNp: evenNn: even J
Z < 83 J
F ª O + eb+
slide 66
Analysis of Nuclear StabilityBoron-12 is radioactive.1) Analyze all 3 factors of stability & determine which
need to be changed2) Predict decay pathway and product3) Reanalyzed the 3 factors of stability to determine if
they are now acceptable
slide 67
Analysis of Nuclear StabilityPolonium-209 is radioactive.1) Analyze all 3 factors of stability & determine which
need to be changed2) Predict decay pathway and product3) Reanalyzed the 3 factors of stability to determine if
they are now acceptable
slide 68
Backup Slides
slide 69
Check for Understanding
N ª C + e
Before AfterResults Analysis Result Analysis
n 6 7p 7 6
n/p ratio L Jodd/even p odd
n even K p evenn odd K
Z < 83 J < 83 J
Predict the decay pathway for nitrogen-13
slide 70
Check for Understanding
H ª He + e
Before AfterResults Analysis Result Analysis
p 1 2n 2 1
n/p ratio L Lodd/even p odd
n even K p evenn odd K
Z < 83 J < 83 J
Predict the decay pathway for hydrogen-3
JKL
slide 71
Independent Practice
C ª N + e
Before AfterResults Analysis Result Analysis
n 8 7p 6 7
n/p ratio L Jodd/even p even
n even J p oddn odd L
Z < 83 J < 83 J
Predict the decay pathway for carbon-14
slide 72
Independent Practice
Rn ª Po + He
Before AfterResults Analysis Result Analysis
n 127 125p 86 84
n/p ratio J Jodd/even p even
n odd K p evenn odd L
Z > 83 L > 83 L
Predict the decay pathway for radon-222
slide 73
Review of Objective
SWBAT explain the factors that influence nuclear stability, the characteristics of the band of stability, and predict the radioactive decay path of a nuclei based on these principles
slide 74
Pathways to Nuclear Stability
type process Δp Δn impact when utilized
a decay à ‒2 ‒2 Z falls Z > 83
b decay n à p + e‒ +1 ‒1 n/p falls high Nn
positron emission p à n + e+ ‒1 +1 n/p rises high Np
electron capture p + e‒ à n ‒1 +1 n/p rises high Np
slide 75
Nuclei Decay to Become Stable
slide 76
slide 77
Outline 1• Why are some nuclei stable and others
radioactive?• Nuclear stability
– What are the natural forces & what is strong nuclear force– balance between strong nuclear attraction & electrostatic
repulsion– neutrons help stabilize because they contribute to strong
nuclear attraction without contributing electrostatic repulsion
slide 78
Outline 2• Band of Stability
– Lighter nuclei are stable with a (n/p) ratio of 1:1– Heavier nuclei are stable with a (n/p) ratio of 1.5:1– Even numbers of protons & neutrons are more stable– No nuclei with >83 protons is stable wrt radioactive decay
• Nuclei outside the band of stability want in– >2000 nuclei known, only 279 are stable– Above the band, get rid of some neutrons– Below the band, get rid of some protons– >83 protons, get rid of protons and neutrons
slide 79
Do Now• Below are two nuclear processes.
A. How would each one change a nucleus? B. What is the name of each process? C. Under what circumstances would a nucleus want to
undergo each process?
slide 80
‒+neutron
in the nucleusproton
in the nucleuselectronemitted
slide 81
Nuclei Decay to Become Stable
slide 82
slide 83
Decay Trends on Graph
slide 84
slide 85
Note• The following examples have been chosen
because their radioactive decay pathways are easily predicted
• It is often difficult to predict if a nuclei will be radioactive, and if so, its pathway of decay
• Often the instability of the nuclei is caused by a concert of multiple factors
• Radioactivity and radioactive decay pathways are usually determined experimentally