Nuclear Chemistry - mscurransclasses

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Nuclear Chemistry
Radioactive Decay
Nuclear Symbols
Element
symbol
Mass number
(p+ + no)
235
92
U
Atomic number
(number of p+)
Nuclear Reactions
A nuclear reaction is a change in the composition or make-up of
the nucleus.
 There are three types of nuclear reactions:
1) Fusion: Combining of nuclei into a larger nuclei
2) Fission: Splitting of an atom
3) Radioactivity: The breakdown of nuclei by giving off
particles
or rays.
http://www.youtube.com/watch?v=Dj4CTJy6U9M
Nuclear
Stability
Decay will occur in
such a way as to return
a nucleus to the band
(line) of stability.
Alpha
Radiation
Alpha decay is
limited to VERY
large, nuclei such as
those in heavy
metals.
Beta
Radiation
Beta decay converts
a neutron into a
proton and electron.
Symbol
Alpha Particle
Emission
4
4
2
OR 2
a
He
Beta Particle
Emission
0
0
OR 1
1
e

How it changes the Decreases the mass Converts a neutron
nucleus number by 4 and the into a proton and
atomic number by 2. increases the atomic
number by 1.
Penetration and
Danger
Protection provided
by…
Gamma Ray
Emission
0
0

No change to the
nucleus.
Low
Medium
High
Skin, Paper
Aluminum, Wood
Concrete, Lead
Diagram showing penetrating ability
www.epa.gov
Types of Radioactive Decay and Balancing
Nuclear Reactions
The Law of Conservation of Mass Number and the Law
of Conservation of Charge allows us to predict products
in a nuclear reaction.
alpha production (a, He): helium nucleus
U  He 
238
92
4
2
234
90
Th
beta production (, e):
Th 
234
90
234
91
Pa  e
0
1
 gamma ray production ():
Th* ®
230
90
Th+ g
230
90
0
0
Practice!
• After completing #6 on your notes sheet,
bring your it up to me so I can check your
answers.
• Once your answers have been checked, get
into your assigned group of approximately
three students and complete the POGIL
(Process Oriented Guided Inquiry Learning)
activity with your partners.
EXIT TICKET:
Predicting products
Predict the products for the following two nuclear
equations.
1)
2)
EXIT TICKET:
Predicting products
Predict the products for the following two nuclear
equations.
1)
2)
Using Half-life
The half-life is defined as the time that it takes for one half
of a sample of a radioactive element to decay into another
element.
Radium-226 has a halflife of 1600 years.
Starting with a 100g
sample, after 1 halflife (or 1600 years),
50g remain.
After another 1600
years, half of the 50g
will remain (25g).
Sample Half-life Problem
A 10 gram of sample of Iodine-131undergoes  decay, what will be
the mass of iodine remaining after 24 days?
The half life of iodine is determined to be approximately 8 days.
That means that 24 days is equivalent to 3 half-lifes.
The decay of 10 grams of I-131 would produce:
1.25 grams of I-131 would remain after 24 days.
Do Now
• Use a marker to write your name in LARGE PRINT
on the blank side of the cardstock.
• On the back side of the cardstock label the element
symbol, atomic number, and mass number.
• Define atomic number and mass number.
Carbon-14 Dating
The age of objects that were once alive can be determined by
using the C-14 dating test. In this test, scientists determine
how much C-14 is left in a sample and from this determine the
age of the object.
From Table N we can determine that C-14 undergoes 
decay:
Where does the Carbon-14 come
from?
C-14 is created in the
atmosphere by cosmic
rays.
It becomes part of living
things through
photosynthesis and the
food chain.
When the plant or animal
dies, the C-14 begins to
decay.
Using C-14 to Age Objects
By comparing the amount of C-14 left in a sample to the amount that was
present when it was alive, and using the half-life of 5700 years (Table N),
one can determine the age of a sample.
Uranium-238 Series
The Uranium-238 Decay Series is used to determine the age of rocks.
In this series, the
ratio of the U-238
to the Pb-206 is
used to determine
the age of the
rock.
“Parent-daughter” Relationship
Aging moon rocks
NASA astronauts have retrieved 842
pounds (382 kg) of moon rocks (in
many missions), which have been
closely studied. The composition of the
moon rocks is very similar to that of
Earth rocks. Using radioisotope dating,
it has been found that moon rocks are
about 4.3 billion years old.
Sample Half-life Problem 2
A sample of a piece of wood is analyzed by C-14 dating. The percent of
C-14 is found to be 25% of what the original C-14 concentration was.
What is the age of the sample?
First, let’s analyze how many half-lives have taken place.
Two half-lives have gone by while the sample decayed from the
original C-14 concentration to 25% of that concentration.
Based on Table N, the half-life of C-14 is 5730 years, so…
Your turn!
On a sheet of paper, answer the following questions from
your textbook. Indicate how you arrived at your answer
and turn in your work for a homework/quiz grade.
Page 670
•Questions 34 (a and b), 36, 37, 38, 41, 42.
Page 671
• Questions 50, 58, 59
The End
• This is the end of the first slide show on
nuclear reactions. You may continue
learning about nuclear reactions by viewing
the second show:
Nuclear Chemistry:
Fission and Fusion
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