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Nuclear Chemistry
“Nuclear radiation is in the form of
elementary particles emitted by
an atomic nucleus, as alpha rays,
beta rays, or gamma rays,
produced by decay of radioactive
substances or by nuclear fission.”
Absorption of Radiation
 = alpha particle Weak energy
 = beta particle Moderate energy
 = gamma radiation High energy
Timberlake, Chemistry 7th Edition, page 84
Characteristics of Some Ionizing Radiations
Characteristics of Some Ionizing Radiation
Property
Alpha radiation
Beta radiation
Composition
Alpha particle
(helium nucleus)
Beta particle
(electron)
High-energy electromagnetic radiation
Symbol
, He-4
, e

Charge
2+
1-
0
Mass (amu)
4
1/
0
Common source
Radium-226
Carbon-14
Cobalt-60
Approximate
energy
5 MeV*
0.05 to 1 MeV
1 MeV
Penetrating
power
Low (0.05 mm
body tissue)
Moderate (4 mm
body tissue)
Very high (penetrates
body easily)
Shielding
Paper, clothing
Metal foil
*(1 MeV = 1.60 x 10-13 J)
Gamma radiation
1837
https://www.youtube.com/watch?v=uJ3ea9fa6CA
Lead, concrete
(incompletel shields)
RADIOACTIVITY
Spontaneous emission of particles (alpha, beta, neutron) or radiation
(gamma), or both at the same time, from the decay of certain
radioisotopes.
Isotopes of some elements are radioactive, especially the large
elements.
Radioactive elements are unstable and will undergo radioactive decay.
These radioactive elements release particles (alpha and beta) in order
to stabilize.
Radioactive decay results in the release of particles and the formation
of an isotope of a new element.
In additions to particles being released, sometimes gamma radiation is
released.
HALF LIFE
• Amount of time it takes
to decay ½ of a sample.
• Varies from milliseconds
to billions of years.
This is always the slope
on a half life graph
• Start with 1.6 g of 187Er
with a half-life of 400
seconds.
• How many grams after 3
half-lifes?
• How much time does it
take to have 0.025
grams?
• How many half-lifes to
get to 0.00625?
HALF LIFE
Number of Mass
half life
Time s
%
Fraction/
ratio
0
1.6
0
100
1
1
0.8
400
50
.5
2
0.4
800
25
.25
3
0.2
1200
12.5
.125
4
0.1
1600
6.25
.0625
5
0.05
2000
3.125
.03125
6
0.025
2400
1.5625
.015625
You can make a chart to determine the mass, number of half life,
time, percent and fraction remaining.
Number of half life, %, and Fraction are the same on every chart.
HALF LIFE
1.Number 2.Mass
of half life
3.Time s
4.%
5.Fraction
/ratio
0
1.6
0
100
1
1
0.8
400
50
.5
2
0.4
800
25
.25
3
0.2
1200
12.5
.125
4
0.1
1600
6.25
.0625
5
0.05
2000
3.125
.03125
6
0.025
2400
1.5625
.015625
How to fill in the
chart
1.Number of half lifeadd 1 to each row.
2.Mass-Divide each
row’s mass by 2
3.Time-Add time to
each row.
4.%- always start
with 100 at 0 time
and divide each row
by 2.
5. Fraction or ratioalways start with 1
and divide each row
by 2.
HALF LIFE
A radioisotope will decay ½ of
the mass of its sample during the
first half life.
 The mass of the radioactive
sample is ½ of the starting mass.
 The mass of the nonradioactive sample has
increased.
What is the half life of the
sample?
If the starting mass was 10 g,
how many g remain after 30
years?
How many years will it take to
reduce the sample to 0.078 g?
ALPHA DECAY
• Alpha decay is the process
of releasing an alpha particle
(He nucleus) from the
nucleus of a radioisotope.
• The result of alpha decay
is a reduction of the
mass number by 4 and
the atomic number by 2
• The equation is written
using isotope notation.
• Both sides of the arrow
are equal in mass and
number of protons
http://www.youtube.com/watch?v=J8p7OIdyt54
Release
of an
alpha
particle,
He
nucleus.
Alpha Decay
U 
 He
238
92
4
2
2

234
90
Th
https://www.youtube.com/watch?v=oFdR_yMKOCw
Timberlake, Chemistry 7th Edition, page 87
ALPHA DECAY
240
94
All numbers are equal on each
side of the arrow.
240 240
94
94
The addition of the mass numbers on the
left and right of the arrow are equal.
The addition of the atomic numbers on
the left and right of the arrow are equal.
Pu 236U + 4He
92
u
2
BETA DECAY
56
The product of this decay
is an atom with the same
mass but 1 more proton
and an electron.
• Beta decay is the release
of a beta particle
(electron) from the
nucleus of an atom.
• WHAT??? How does an
electron come out of the
nucleus if they are in the
energy levels???
• Are you ready for this?
A neutron changes into a
proton and an electron.
After all, a positive and a
negative make it neutral.
Beta Decay
Changes a neutron into a proton and an electron. The electron
is released as a beta particle.
Timberlake, Chemistry 7th Edition, page 90
Alpha and Beta Emission
Alpha Decay
ALPHA
Element
down 2
protons and
mass of 4
Beta Decay
https://www.youtube.com/watch?v=o-9yt7OAYmE
BETA
Element
increases 1
proton and
keeps same
mass
Alpha and Beta Emission
BETA PLUS DECAY
• The symbol for a
positron is e+.
• PET-positron emission
tomography is a scan
used to find cancer.
• Are you sitting down?
Now we have a POSITIVE
electron. It is called a
positron.
Positron decay is like a
mirror
image of beta
decay.
1) A proton to become a
neutron.
2) It emits a positron
3) The atomic number goes
DOWN by one and mass
number remains
unchanged.
ELECTRON CAPTURE
• 3) The atomic number
goes down by 1 and
mass number stays the
same.
• Electron capture is not
like any other decay alpha, beta, or position.
All other decays shoot
something out of the
nucleus.
• 1) An electron from the
closest energy level falls
into the nucleus, which
causes a proton to
become a neutron.
• 2) A neutrino(neutral
particle with no mass) is
emitted from the
nucleus.
IMPORTANT: MASS AND CHARGE =
ON BOTH SIDES OF ARROW!
4+10 = 13+1
2+5 = 7+0
New Radioactive
Isotope
Timberlake, Chemistry 7th Edition, page 92
NUCLEAR FISSION
Nuclear Fission is the splitting of a radioactive isotope by
bombardment with neutrons so that the atom splits into smaller
elements with a release of energy.
NUCLEAR FISSION
When a nucleus fissions, it splits into
several smaller fragments. These
fragments, or fission products, are
about equal to half the original mass.
Two or three neutrons are also
emitted.
The sum of the masses of these
fragments is less than the original
mass. This 'missing' mass (about 0.1
percent of the original mass) has
been converted into energy according
to Einstein's equation.
Fission can occur when a nucleus of a
heavy atom captures a neutron, or it
can happen spontaneously.
Fissionable U-235
• A nuclear chain reaction occurs when
one nuclear reaction causes an average
of one or more nuclear reactions, thus
leading to a self-propagating number of
these reactions. The nuclear reaction is
the fission of heavy isotopes.
• The nuclear chain reaction is unique
since it releases several million times
more energy per reaction than any
chemical reaction.
http://www.youtube.com/watch?v=FQGtpo2IUxA&NR=1&feature=fvwp
•
https://www.youtube.com/watch?v=0v8i4v1mieU
http://www.youtube.com/watch?v=Pmy5fivI_4U
Chain reaction
Fission Process
NUCLEAR POWER PLANTS
Electricity in Illinois is about 50% coal generated and 50% nuclear
power generated.
NULCEAR POWER
ILLINOIS
Nuclear Reactor
https://www.youtube.com/watch?v=rBvUtY0PfB8
Nuclear Power Debate
Cons
• Radiation exposure
possible from accident or
terrorist
• No where safe to bury
waste
• Moving waste a potential
danger
• Thermal pollution
• Long time to build nuclear
plants
• U will be depleted
•
https://www.youtube.com/watch?v=BdbitRlbLDc
•
https://www.youtube.com/watch?v=AkHLQfe3dw4
https://www.youtube.com/watch?v=VJfIbBDR3e8
Pros
No greenhouse gases
 Very little solid waste
 Less extensive mining to
extract U
 Less air pollution
 Generate large amounts of
electricity from a single plant
Nuclear Fusion
+
1
4H
1
4 H nuclei

+
0
2 e
-1
2 electrons
4
1 He2
HeEnergy
+
FISSION
FUSION
• Splits atoms
• Combines atoms
• Releases radiation
• No radiation
• Used in nuclear power plants
• On the sun
FISSION AND FUSION
• Release of large amounts of energy
• Changes in the nuclei of atoms
FISSION VS. FUSION
•
•
•
•
•
•
•
•
•
•
•
detect leaks in pipelines.
attacking abnormal cells or harmful bacteria.
treat cancer
preserve food
sterilize medical instruments
tracer in medical research
studies of human metabolism.
Military
home smoke detectors.
calculate the age of mineral
Pest control
OTHER USES FOR RADIOISOTOPES