Download Nuclear Chemistry - Solon City Schools

NUCLEAR CHEMISTRY
1
Nuclear Chemistry
At the conclusion of our time together,
you should be able to:
1. List 4 people who contributed to the discovery of
radiation and their contribution
2. List the subatomic parts of the atom including
quarks
3. Explain the difference in isotopes of an atom
4. Explain alpha, beta, and gamma radiation and
what happens to the nucleus
5. Calculate half-lives of radioactive materials
6. List differences between a fusion and fission
reactions
2
3
Interesting Signs:
Nuclear Chemistry
At the conclusion of our time together,
you should be able to:
1. List 4 people who contributed to the discovery of
radiation and their contribution
4
The People Behind the Discovery of
Radiation
5
Roentgen (1895)
•Studied fluorescent materials that
glowed when hit with a beam of
electrons.
•Discovered a mysterious form of
radiation was given off even
without electron beam. This
radiation could pass through paper
and other objects but not dense
materials (lead, bone).
•Called them X-rays
6
Becquerel (1896)
•Studied fluorescent minerals
containing uranium.
•Discovered radioactivity by
accident on a cloudy day:
•Thought that an external
source was needed to
produce the mysterious
radiation.
•Found that uranium emits
radiation without external
source.
7
8
All You Really Need To Know
You Can Learn From Noah's Ark
7. For safety's sake, travel in pairs.
8. Two heads are better than one.
Pierre and Marie Curie
Thought radioactivity was a
property of heavy elements.
During study, discovered new
radioactive elements:
Polonium and Radium.
Wondered how a small mass
can give off a large amount
of energy:
Explained by Einstein with E=mc2.
9
Mass Defect
• Difference between the mass of an atom
and the mass of its individual particles.
4.00260 amu
4.03298 amu
10
Mass Defect
• Some of the mass can be converted into energy
• Shown by a very famous equation!
E=mc2
Energy
Mass
Speed of light
11
Nuclear Binding Energy
• Energy released when a nucleus is formed
from nucleons.
• High binding energy = stable nucleus.
E = mc2
E: energy (J)
m: mass defect (kg)
c: speed of light
(3.00×108 m/s)
12
Nuclear Binding Energy
Unstable nuclides are radioactive and
undergo radioactive decay.
13
14
Rutherford
•Studied radioactivity and named types of nuclear
radiation.
•Discovered that elements decay into other
elements after emitting nuclear radiation. Called it
Nuclear Decay.
•Gold foil experiment revealed that the mass of an
atom is concentrated in the nucleus (atom is mostly
space)
15
Radiation
So let’s see if you can:
1. List 4 people who contributed to the discovery of
radiation and their contribution
16
Review of the Atom and Isotopes
17
Review of Atoms and Isotopes
At the conclusion of our time together,
you should be able to:
1. List the subatomic parts of the atom including
quarks
2. Explain the difference in isotopes of an atom
18
19
Euphemisms in Science
We all know that some politicians and government spokesmen
use certain euphemistic phrases to give an aura of respectability
to descriptions of events or actions which would be offensive
when expressed in plain English. The following is a list of
Euphemisms in Science and their translations into plain English.
“It is clear that much additional work will be required
before a complete understanding...”
I don't understand this at all!
The Atom
• An atom is the smallest particle of an
element that has the chemical properties
of the element.
• The atom is extremely small. One teaspoon of
water has 3 times as many atoms as the Atlantic
Ocean has teaspoons of water.
• If a large sports stadium were an atom, a
marble on the 50 yard line would represent the
nucleus.
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21
The Atom
An atom consists of a
• nucleus
– (of protons and neutrons)
• electrons in space about the nucleus.
Electron Cloud
Nucleus
ATOMIC COMPOSITION
• Protons (p+)
– + electrical charge
– mass = 1.672623 x 10-24 g
– relative mass = 1.007 atomic mass units (amu)
but we can round to 1
22
ATOMIC COMPOSITION
• Electrons (e-)
– negative electrical charge
– relative mass = 0.0005 amu
– but we can round to 0
• Neutrons (no)
– no electrical charge
– mass = 1.009 amu
– but we can round to 1
23
Mass Comparison
24
Proton is about
2000 x electron
Electron is about
1,000,000 x photon
-1
e
.
Proton
Electron
Photon
Familiar Saying
Eschew the implement of correction and vitiate
the scion.
Spare the rod, spoil the child!
25
26
Atomic Number, Z
All atoms of the same element have the same
number of protons in the nucleus, Z
13
Al
26.981
Atomic Number
Atomic Symbol
Average Atomic Mass
27
Mass Number, A
• C atom with 6 protons and 6 neutrons is the
mass standard
• = 12 atomic mass units (amu)
• Mass Number (A)
= # protons + # neutrons
• NOT on the periodic table
• It is the Average atomic mass (which is on the
periodic table) rounded to the nearest whole
number
28
In Summary
• Atomic number = the # protons and also
the # electrons
• Mass Number
= average atomic number
rounded to the nearest
whole number
• Mass Number
= # protons + # neutrons
Remember Isotopes??
1H
2H
3H
29
30
Isotopes
Atoms of the same element
(same number of protons) with a different number of neutrons.
1H
2H
3H
31
Isotopes
12C
13C
6 Protons
6 Protons
6 Neutrons
7 Neutrons
32
Isotopes
Therefore:
The Average Atomic Mass will be some fraction between all
the mass numbers of all the isotopes of that element!
For Hydrogen, since most of the isotopes of are in the left
form, the average atomic mass is slightly more than 1 amu.
1H
2H
3H
33
To: Santa Re: Where Are My Gifts?!
Actual E-mails to EmailSanta.com
• I’m sorry for putting all that Ex-lax in your milk last
year, but I wasn’t sure if you were real.
• My dad was really mad.
• Bri, 7
34
Tevatron - world's highest-energy particle
accelerator.
Four miles in circumference
Particles go around at 99.9999% of the speed
of light.
35
Particle
accelerator
36
We send protons and antiprotons in
opposite directions, and smash
them together.
37
We’ve Discovered Other Particles
Matter
anti-Matter
Example:
electron
positron
e-1
e+1
38
We’ve Discovered Other Particles
Matter
anti-Matter
Example:
Proton
+1
P
anti-Proton
-1
P
39
We’ve Discovered Other Particles
Quarks
Up
2
3
Leptons
electron
e-1
Down
-1
3
40
41
Sub-Subatomic Particles
• Quarks
• Sum of the charges is the
electrical charge
• Fast moving points of
energy
 Up quark
= + 2/3
 Down quark = - 1/3
He
42
Structure of Sub-Subatomic Particles
Quark Calculations of Charges
Each proton is 2 up quarks and 1 down quark
2(2/3) – 1(1/3) = 4/3 – 1/3 = 3/3 or +1
Each neutron is 2 down quarks and 1 up quark
2(-1/3) + 2/3 = 0
Each electron is composed of 3 down quarks
3(-1/3) = -1
43
A.P. TEST IN ADVANCED BIOLOGY
•
• You have been provided with a razor blade,
a piece of gauze, needle and thread and a
bottle of scotch. Remove your appendix.
Do not suture your work until it has been
inspected. You have 15 minutes.
Review of Atoms and Isotopes
Let’s see if you can:
1. List the subatomic parts of the atom including
quarks
2. Explain the difference in isotopes of an atom
44
45
Self-Check
Isotope
Mo-101
H-2
C-14
U-238
Bi-210
He-4
Symbol
101
42
2
1
14
6
238
92
210
83
4
2
Mo
H
C
U
Bi
He
# protons
# neutrons
Atomic Mass
42
59
101
1
1
2
6
8
14
92
146
238
83
127
210
2
2
4
46
Proton
Mass
Charge
Neutron Electron
1 amu
1 amu
0 amu
+1
0
-1
47
What is
d
Made of
3 Quarks
1 up
2 down
u
Neutron
d
48
What is
u
Made of
3 Quarks
2 up
1 down
d
Proton
u
Bill Gates' Rules
Here is a list of 11 things that many high
school and college graduates did not learn in
school. In his book, Bill Gates talks about how
feel-good, politically-correct teachings
created a full generation of kids with no
concept of reality and how this concept has
set them up for failure in the real world.
RULE 4
If you think your teacher is tough, wait till you get a
boss. He doesn't have tenure.
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Nuclear Reactions and Half-Life
At the conclusion of our time together,
you should be able to:
1. Explain alpha, beta, and gamma radiation and
what happens to the nucleus
2. Balance 5 different types of nuclear reactions
3. Calculate half-lives of radioactive materials
50
Nuclear Reactions vs. Normal
Chemical Changes
• Nuclear reactions involve the nucleus
• The nucleus opens, and protons and
neutrons are rearranged
• The opening of the nucleus releases a
tremendous amount of energy that holds the
nucleus together – called what?
• Binding energy
• “Normal” Chemical Reactions involve
electrons, not protons and neutrons
51
52
Types of Radiation
• Alpha (ά) – a positively charged
helium isotope - we usually
ignore the charge because it
involves electrons, not protons
and neutrons
4
2
He
•Beta (β) – an electron
0
1
•Gamma (γ) – pure energy; called
a ray rather than a particle
0
0

e
53
Other Nuclear Particles
• Neutron
1
0
• Positron – a positive electron
0
1
•Proton – usually referred to as
hydrogen-1
1
1
•Any other elemental isotope
n
e
H
54
Chemical Compound Quiz
Sodium hydrogen carbonate gives a nice lift to biscuits.
What is the common name?
Baking Powder
55
Penetrating Ability of Radiation
Radioactivity
Positron
emission
56
Radioactive Particles And Rays
Alpha Particle
2 Protons
2 Neutrons
57
58
Radioactive decay
Radioactivity
Change in the nucleus of an atom
Loss of an Alpha, Beta, or Gamma particle
3 Forms of Radioactive Decay
Alpha
emission
Changes
Atomic
Mass
2P 2N
Beta
emission
Neutron
turns into
a Proton
electron
Gamma
emission
light
59
Balancing Nuclear Reactions
•In the reactants (starting materials – on the
left side of an equation) and products (final
products – on the right side of an equation)
Atomic numbers must balance
and
Mass numbers must balance
•Use a particle or isotope to fill in the missing
protons and neutrons
60
61
15 Helpful Hints On The Lab Report from
Mr. T’s Vast Lab Experience!!!
Hint #15. When your calculated answers don't
match the answer you should have gotten
utilize the TF2 constant.
TF2 constant (Toburen Fudge Factor):
that quantity which, when multiplied by, divided by,
added to or subtracted from the answer you got, gives
you the answer you should have gotten.
62
Alpha Emission
occurs when the nucleus
has too many protons
which cause excessive
repulsion.
238
234
92
90
U
parent
nuclide
Th  He
daughter
nuclide
4
2
alpha
particle
Numbers must balance!!
63
Alpha Emission
Ex. Plutonium-239 undergoes alpha decay
239
94
Atomic Mass:
Atomic #:
235
92
Pu
U
+
4
2
He
239
=
235
+
4
94
=
92
+
2
Masses must be equal = Conservation of mass
64
Beta Emission
occurs when the neutron to proton ratio is
too great.
131
53
I
131
54
Xe  e
0
-1
electron
65
Remember Quark Charges
Beta Emission Means a Neutron becomes a Proton
Each electron is composed of 3 down quarks
3(-1/3) = -1 (Lost)
Each neutron is 2 down quarks and 1 up quark
2(-1/3) + 2/3 = 0 - 3(-1/3) = +1
Neutron becomes a proton
Therefore, mass number stays the same but atomic
number goes up one!
Neutron to Proton
66
67
Beta Emission
Ex. Polonium-210 undergoes beta decay to
produce this daughter nuclide
210
84
Atomic Mass:
Po
210
-
210
Atomic #:
A
Z
0
=
=
1
=
=
84
84
A
Z
+
X
=
X
+
A
A
0
+
-1
=
210
Z
+
Z
=
210
85
At
85
0
-1
e
68
Positron Emission
Occurs when the neutron to proton ratio is too
small.
38
19
K  Ar  e
38
18
0
1
positron
69
Positron Emission
Ex. Polonium-210 undergoes positron emission to
produce this daughter nuclide
210
84
Atomic Mass:
Po
210
-
210
Atomic #:
A
Z
0
=
=
1
=
=
84
84
A
Z
-
X
=
X
+
A
A
0
+
1
=
210
Z
+
Z
=
210
83
Bi
83
0
+1
e
Electron Capture
70
occurs when the neutron to proton ratio in the
nucleus is too small.
106
47
Ag  e 
0
-1
106
46
Pd
electron
Electron Capture
Ex. Polonium-210 captures an electron to
produce this daughter nuclide
210
84
Po
Atomic Mass:
0
+
-1
210
A
Z
e
+
0
A
Atomic #:
84
+
-1
Z
A
Z
X
=
=
=
=
=
A
210
Z
83
210
83
Bi
X
71
Murphy's Laws
of
Science and Technology
A meeting is an event in which minutes are kept
and the hours are lost.
72
Gamma Emission
occurs when the nucleus is at too high an
energy.
Emission of high energy electromagnetic
wave.
73
74
75
Gamma Emission
Ex. Polonium-210 undergoes gamma decay
to produce this daughter nuclide
210
84
Atomic Mass:
Atomic #:
A
Z
Po
A
=
=
Z
=
=
210
84
A
Z
X
=
X
+
0
0
A
+
0
Z
+
0
210
84
210
84
Po

76
Now Lets’
Consider
Nuclear Decay
and Half-Life
Band of
Stability and
Radioactive
Decay
77
Nuclear Decay
• Why nuclides decay
– need stable ratio of
neutrons to protons
•Transmutation-One
element becomes another.
238
92
U
I
131
54
K
38
18
131
53
38
19
106
47
Th  He
234
90
4
2
Xe  -10 e
Ar 
Ag  e 
0
-1
0
1
106
46
e
Pd
More than 83 protons
means that the nuclei is
unstable (radioactive)
78
Half-life
• Half-life (t½)
– Time required for half the atoms of a
radioactive nuclide to decay.
– Shorter half-life = less stable.
79
Half-life
mf  m ( )
1 n
i 2
mf:
mi:
n:
final mass
initial mass
# of half-lives
80
Half-life
 Fluorine-21 has a half-life of 5.0 seconds. If you
start with 25 g of fluorine-21, how many grams
would remain after 60.0 s?
GIVEN:
WORK:
t½ = 5.0 s
mi = 25 g
mf = ?
total time = 60.0 s
n = 60.0s ÷ 5.0s =12
mf = mi (½)n
mf = (25 g)(0.5)12
mf = 0.0061 g
81
Interesting Signs:
Nuclear Reactions and Half-Life
Let’s see if you can:
1. Explain alpha, beta, and gamma radiation and
what happens to the nucleus
2. Balance 5 different types of nuclear reactions
3. Calculate half-lives of radioactive materials
82
83
Penetrating Ability
Types of Radiation?
• Alpha particle ()
– helium nucleus
84
Charge Shielding
4
2
He
2+
• Beta particle (-)
– electron
0
-1
1-
• Positron (+)
– positron
0
1
• Gamma ()
– high-energy photon
0
0
e
e

paper
lead
1+
0
concrete
85
Alpha Emission
Ex. Polonium-210 undergoes alpha decay to
produce this daughter nuclide
210
84
Atomic Mass:
Po
210
-
210
Atomic #:
A
Z
4
=
=
2
=
=
84
84
A
Z
-
X
=
+
A
A
+
X
=
206
Z
+
Z
=
206
82
Pb
82
4
2
4
2
He
Remember in Nuclear Reactions
• Alpha emission
Note that mass number (A) goes down by 4 and
atomic number (Z) goes down by 2.
Nucleons (nuclear particles… protons and
neutrons) are rearranged but conserved
86
Remember in Nuclear Reactions
• Beta emission
Note that mass number (A) is unchanged and
atomic number (Z) goes up by 1.
87
Remember the Other Types of Nuclear
Reactions
Positron (0+1): a positive electron
207
Electron capture: the capture of an electron
207
88
89
The “Y” Generation!!!
90
Learning Check
What radioactive isotope is produced in the
following bombardment of boron?
10B
5
+ 4He
? +
2
1n
0
13Li
7
91
Write Nuclear Equations!
Write the nuclear equation for the beta
emitter Co-60.
60Co
27
-
0e
-1

60Ni
28
92
What is Half-Life?
• HALF-LIFE is the time that it takes for 1/2 a
sample to decompose.
• The rate of a nuclear transformation depends only
on the “reactant” concentration.
93
Half-Life
Decay of 20.0 mg of 15O. What remains after 3
half-lives? After 5 half-lives?
Kinetics of Radioactive Decay
For each duration (half-life), one half of the
substance decomposes.
For example: Ra-234 has a half-life of 3.6 days
If you start with 50 grams of Ra-234
After 3.6 days > 25 grams
After 7.2 days > 12.5 grams
After 10.8 days > 6.25 grams
94
95
Learning Check!
The half life of I-123 is 13 hr. How much of a
64 mg sample of I-123 is left after 39 hours?
mf  m ( )
1 n
i 2
X mg = 64 (1/2)3
8.0 mg
96
Another Interesting Sign:
Radiation
At the conclusion of our time together,
you should be able to:
1. List differences between a fusion and fission
reactions
97
Nuclear Fission
98
Nuclear Fission
Fission is the splitting of atoms
These are usually very large, so that they are not as
stable
Fission chain has three general steps:
1. Initiation. Reaction of a single atom starts the
chain (e.g., 235U + neutron)
2. Propagation.
236U
fission releases neutrons that
initiate other fissions
3. ___________ .
99
Representation Of A Fission Process.
100
Nuclear Fission & POWER
• Currently about 103
nuclear power plants in
the U.S. and about 435
worldwide.
• 17% of the world’s
energy comes from
nuclear.
101
Diagram Of A Nuclear Power Plant.
102
103
Nuclear Fusion
Fusion
small nuclei combine
2H
1
+
3H
4He
1
2
+ 1n +
0
Occurs in the sun and other stars
Energy
104
Nuclear Fusion
Fusion
• Excessive heat can not be contained
• Attempts at “cold” fusion have FAILED.
• “Hot” fusion is difficult to contain
105
Geiger Counter
• Used to detect radioactive substances
106
Effects of Radiation
107
108
When I was a kid…
• We didn’t have padding under our jungle gyms.
We had rocks!
• We didn’t have safety belts on our swing sets.
The whole goal was to get as high as you could
and then launch yourself.
• We rode our bikes without helmets.
• No sunscreen, just suntan lotion, and got burned to
a crisp.
109
When I was a kid…
•
•
•
•
We played with BB guns.
Ran with scissors.
Blew up Barbie dolls with M-80’s.
Wore Halloween costumes with asbestos.
• But for safety….
• our moms made us wait an hour after we ate
before we went swimming!!!!
Radiocarbon Dating
Radioactive C-14 is formed in the upper atmosphere
by nuclear reactions initiated by neutrons in
cosmic radiation
14N + 1 n ---> 14C + 1H
o
The C-14 is oxidized to CO2, which circulates
through the biosphere.
When a plant dies, the C-14 is not replenished.
But the C-14 continues to decay with t1/2 = 5730
years.
Activity of a sample can be used to date the sample.
110
Artificial Nuclear Reactions
New elements or new isotopes of known elements
are produced by bombarding an atom with a
subatomic particle such as a proton or neutron
-- or even a much heavier particle such as 4He
and 11B.
Reactions using neutrons are called
 reactions because a  ray is usually emitted.
Radioisotopes used in medicine are often made by
 reactions.
111
Artificial Nuclear Reactions
Example of a  reaction is production of
radioactive 31P for use in studies of P uptake in
the body.
31
15P +
0n 
1
32 P
15
+ 
112
Transuranium Elements
Elements beyond 92 (transuranium) made
starting with an  reaction
238 U
92
+
239 U
92
239
93Np
1
0n
+ 

239
92U

239
0 
Np
+
93
-1

239
94Pu +
0
-1
113
Nuclear Medicine: Imaging
Thyroid imaging using Tc-99m
114
115
Food Irradiation
•Food can be irradiated with  rays from 60Co or
137Cs.
•Irradiated milk has a shelf life of 3 months
without refrigeration.
•USDA has approved irradiation of meats and
eggs.
116
Fission or Fusion??
Familiar Saying
One pyrus malus per diem restrains the arrival of the
Hippocratic apostle.
An apple a day keeps the doctor away!!
117
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