Unit: Nuclear Chemistry
Fission, Fusion, and Applications of
Nuclear Chemistry
After today you will be able to…
• Describe what happens in a
nuclear chain reaction.
• Differentiate between fission and
fusion reactions.
• Identify examples of how
radioisotopes are used in
everyday life.
Recall, during transmutations an
atom can be converted into a
different atom through radioactive
decay or by bombarding a nucleus
with particles.
Today, we will focus on the
latter by learning about fission
and fusion.
Nuclear Fission
Fission: occurs when a nucleus is split into
smaller pieces.
• This process begins by colliding a nucleus
with particles such as neutrons.
• The resulting nucleus is highly unstable
and decays.
• This causes a chain reaction where
particles emitted from the initial
reaction bombard other nuclei, causing
them to break apart.
Example: Uranium-235
1
0
n
235
The neutrons
released
U
92
from the decay of U-236
will collide with other
Kr
n
236 U-235 atoms, repeating
ENERG
92 U
n
Y
this process all over
n
again (chain reaction).
Ba
91
36
1
0
1
0
142
56
1
0
Nuclear Fission
• Uranium-235 and
Plutonium-239 are the only
fissionable isotopes.
• These reactions release a
large amount of energy.
Nuclear Fusion
Fusion: occurs when nuclei
combine (or fuse together) to
produce a new nucleus of greater
mass.
• Example: Production of energy
from the sun
1
1
4 H
4
2
He + 2 e +
0
+1
energy
Nuclear Fusion
• Releases far more energy
than fission reactions.
• These reactions require
very high temperatures in
order to occur
(~40,000,000°C).
Real-World Applications: C-14 Dating
Scientists often find the age of an
object that was once living by
measuring the amount of carbon-14 it
contains.
• Recall, C-14 has a half-life of 5730
years.
• This is its nuclear decay:
14
6
C
14
7
0
-1
N + e
Real-World Applications: C-14 Dating
• All living things contain C-12 and C-14 in a
fixed ratio.
• Once an organism dies, the ratio of C-14:C-12
changes, which allows archeologists to
estimate its age.
Real-World Applications: C-14 Dating
• The most
accurate way to
examine the C-14
content is through
use of a mass
spectrometer.
• First, the carbon in the sample must be
converted into graphite or carbon dioxide.
―This is can be done by burning a portion
of the sample.
Real-World Applications: C-14 Dating
• The sample is then
injected into a mass
spectrometer and
ionized.
• Due to the different masses of
carbon having different angles of
deflection, a scientist can count the
individual C-14 atoms in the sample.
Mass Spectrometer:
Real-World Applications: U-238
But what if all of the C-14 in a sample
has decayed or the sample is non-living?
• Similar to carbon-14, uranium-238 is
used to date specimens.
• Uranium is naturally found in most
rocks, seawater, and in Earth’s crust.
• It has a half-life of 4.5 billion years.
• U-238 is specifically used in dating
rocks and fossils.
Real-World Applications: I-131
Radioisotopes can be used
to diagnose medical
problems or treat
diseases.
• Specifically, iodine-131
is a radioisotope given
to patients to check for
abnormal thyroid
function.
• Patients are given a
drink containing the
radioisotope (Na131I).
Real-World Applications: I-131
• Since the thyroid
extracts iodide ions
from the bloodstream,
the ions are absorbed
and its radioactivity is
used to create an
image on a screen.
• From the image, doctors can examine the
amount of iodine absorbed and determine if
a person has hyperthyroidism or thyroiditis.
Real-World Applications: Co-60
The strong penetrating power of
gamma rays allows it to be useful
in the treatment of cancer.
• Cobalt-60, which is produced
in particle accelerators, emits
both beta and gamma
radiation.
Real-World Applications: Co-60
• The Co-60 is placed
into a gun that is
used to direct the
radiation to where
the tumor is located.
• The cells of the tumor are destroyed and it
decreases in size.
• However, gamma radiation can also destroy
healthy cells making those treated very ill.
Questions?
Begin WS4