Pre AP Chemistry (r-13)
Name _____________________________________
Nuclear Chemistry Notes
A. Four Forces of the Universe
1. _________________________________

Attraction between all forms of matter; operates across the universe

Weakest of four forces
2. _________________________________

1024 times stronger than gravity

Responsible for radioactivity
3. _________________________________
 1036 times stronger than gravity
 Attracts or repels charged matter (opposite charges attract, like charges
repel)
4. _________________________________
 1038 times stronger than gravity
 Exerted by protons and neutrons to hold nucleus together
 Acts only over VERY short distances within nucleus to overcome
electromagnetic repulsion
Examples:
What force is involved when you rub a balloon through your hair and it sticks to
the wall?
____________________________
What force is involved when you release the balloon and it falls to the ground?
____________________________
What force is involved when U-235 splits?
____________________________
What force is involved that permits us to estimate the age of fossils using C-14
dating?
____________________________
B. Chemical Reactions vs. Nuclear Reactions
Chemical Reactions
vs
Nuclear Reactions
Occur when bonds between atoms
are broken or formed
Occur when a nucleus is changed and
particles and/or rays are emitted
Atoms are not changed,
just rearranged
Atoms are converted into atoms of
another element; change in # of p+
Involves only valance electrons
Involves protons, neutrons, and
electrons
Small energy changes
VERY LARGE energy changes
Reaction rate is affected by
temperature, pressure,
concentration, and catalysts
Reaction rate unaffected by these
C. Radioactivity

Substances that ____________________ emit radiation are said to be
____________________.

Nucleons = _______________ and _______________

_______________: atoms identified by the number of protons and
neutrons in the nucleus. Example: radium-228 or 228 88 Ra; specific
isotopes such as C-12 and C-13

All ____________________ elements and all elements with atomic
number higher than _____ are unstable and therefore radioactive.
2

Unstable systems gain _______________ by losing _______________.

The primary factor of determining how stable an atom is its ratio of
____________________ to ____________________.

The force that acts on subatomic particles that are extremely close
together and keeps the nucleus together is known as _______________
_______________ _______________ .

Unstable nuclei lose energy through radioactive decay to form a nucleus
with a stable number of _____ and _____

In atoms with low atomic numbers, the proton to neutron ratio in stable
nuclei is +/- __________

In atoms with high atomic numbers, the proton to neutron ratio in stable
nuclei is +/- __________

The Band of Stability:
3

_______________ _______________– the spontaneous process of an
unstable nuclei losing energy by emitting radiation; occurs naturally

Unstable radioactive atoms will undergo radioactive decay until they form
stable atoms, often of a _______________ _______________.
D. Types of Radiation

Isotopes of atoms with unstable nuclei are called ___________________.

During radioactive decay, unstable atoms lose energy by emitting one of
several types of radiation, the three most common are
_______________, _______________, and _______________.
Type of radiation
Greek Symbol
Description
of Radiation
Alpha
Beta
Gamma
α
β
y
Electrons
Photons
Helium Nuclei
Often accompanies alpha
or beta decay
Nuclear Symbol
Charge
Mass
Penetrating
Power
42He
0-1e
00γ
+2
-1
0
4 amu
0 amu
0 amu
Least penetrating
due to large mass
and charge
Can cause harm
through ingestion or
inhalation
Blocked by paper;
cannot penetrate
skin
4
Penetrating ability
100 times greater
than that of alpha
particles
Travels at speeds
close to speed of
light
Blocked by metal
foil
Greatest penetrating
ability
Protection requires thick
layers of lead, concrete,
or both

Example of alpha decay:

Example of beta decay:

Example of gamma radiation:
238
92U

137 Cs
55
4
2 He

+ 23490Th
137 Ba
56
137 Ba
56

+
0 e-1
137 Ba
56
+
0 y
0
E. Writing Nuclear Equations

To write nuclear equations, just make sure the sum of the mass numbers
on the left and right sides of the arrows are the same, and that the atomic
numbers add up too! Think of the → as an =.
226 Ra
88
mass #:
atomic #:
 22286Rn + 42He
226  222 + 4
88  86 + 2
Example #1
Decay of Thorium–230 by alpha emission
Example #2
Decay of Carbon–14 by beta emission
Example #3
238
92
U  42He + _____ + 00y
Example #4
_____ 
129 Xe
54
+
0 e
-1
5
Example #5
_____ +

1 n
0
7 Li
3
Example #6
_____ +
0 e
-1

82 Rb
37
Example #7
238 U + 4 He
92
2
 24094Pu + _____10n
F. Transmutation

Transmutation is the___________________________________________

All _______________ _______________are transmutation reactions

Transmutations can be induced (forced) by _______________ a stable
nucleus with high-energy alpha, beta, or gamma radiation

To overcome the repulsion between charged particles (like alpha particles)
and the target nucleus, the particles must be moved at extremely
____________ ____________

This is accomplished by using a _______________ _______________
(also called Atom Smashers or Super Colliders)
Stanford Linear Accelerator:
 Stanford University in California
 2 miles long
 Operational in1966 (first)
Large Hadron Collider
 Geneva, Switzerland
 Circular 17 mile tunnel (largest)
 Built from 1998 to 2008
G. Transuranium Elements

All elements immediately following Uranium on the periodic table
(#_____ and above) are called the transuranium elements.
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
The transuranium elements were all _______________ _____ _____
_______________ by induced transmutation.
H Half-Life

Not all isotopes ____________ at the same rate

Radioactive decay is _______________ in half-lives

Half-life – the time required for one half of a radioisotope’s nuclei to decay
into its peoducts.
For example: The half -life of strontium-90 is about 25 years. This means if you
had 100.0 g of strontium-90 today, you would have 50.0 g left 25 years from now,
25.0 grams would remain after 50 years, and 12.5 grams would be left after 75
years. The decay would continue until negligible strontium-90 remained.
Common Half-Lives:

Carbon-14 dating is used to measure the age of objects up to 24,000
years old.

Uranium-238 (to lead-206) is used for dating objects for up to several
billion years old.
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Half-Life Calculations
The formula for calculating half-life is:
Mf = (Mi)(.5)n
Where:
Mf = final mass
Mi = initial mass
n = the number of half-lives passed
And: n = total time elapsed
length of 1 half life
or n = _t_
T
Example #1
If Gallium-68 has a half-life of 68.3 minutes, how much of a 20.0 g sample is left
after two half-lives? (3 sf)
Example #2
The half-life of Iron-59 is 44.5 days. If 0.295 mg remains after 23.5 days, what
was the mass of the original sample? (3 sf) Hint: solve for n then plug it into
equation.
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Example #3
What is the half-life of francium-224 if a 200.0 g sample decays to 75.0 g in 12.1
days? (3 sf)
I. Nuclear Reactions and Energy

_______________ _______________are much more efficient at providing
energy than _______________ _______________ _______________

For example: The energy released from the nuclear reaction of _____
_______________ of uranium is roughly equivalent to the energy released
by the chemical combustion of _____ __________ _______________ of
coal!

In nuclear reactions, the mass of the products is less than the mass of the
reactants which seems to violate the Law of Conservation of Mass.

However, the missing mass, known as the _______________
_______________, is converted into energy.

E = mc2
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J. Fission vs. Fusion
Fission

Nuclear ____________ is the ____________ of nuclei

The fission of a nucleus is accompanied by a very large release of
___________

The mass of the products is less than the mass of the reactants. The
missing mass, called the __________ __________, is converted into
energy.

If a sample is large enough to reach ____________ __________, the
particles released from a nuclear reaction can cause a nuclear reaction in
other atoms, causing a __________ ____________
Uranium-235 Fission Reaction:
Fusion

Nuclear _______________ is the ________________ of two or more light,
less stable nuclei (mass < 60) into a single more stable nucleus and the
subsequent release of energy.

Particles must travel at ____________ ____________ ____________ to
fuse

Think of hitting two pool balls at each other so hard that instead of
bouncing off one another, they instead ____________ into one
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
Nuclear fusion is what powers the sun

The sun’s reaction:____________________________________________

In one second, the sun produces more energy than the entire amount of
energy produced by human civilization since its inception!
Advantages of Fusion over Fission

Fusion produces __________ __________ than fission (about 100X)

Fusion does not produce _______________ ____________, fission does

The raw materials for fusion are readily available because hydrogen is one
of the most _______________ elements (think water)
Problems with Fission

_______________ ____________- how and where to store it

Public concern with ____________
Problems with Fusion

_______________- no solid can withstand conditions necessary for
reactions to occur (scientists use magnetic fields to contain plasma)

_______________- at present, as much energy is needed to start a
reaction as is produced
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K. Uses for Nuclear Chemistry

Nuclear Power Plants- heat water to form steam, turns generator magnets

Radioactive Dyes- provide contrast in medical tests

Radiation Therapy - high energy particles kill tumor cells (cancer
treatment)

PET Scans- Positron Emission Tomography; used in mapping brain
function and locating lesions, etc.

Radioisotope Dating- determine ages of fossils, etc.

Nuclear Weapons- The H-Bomb is based on the fusion of Hydrogen
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