1. Nuclear
Chemistry
Topic 12

2. Topic 12-Nuclear Chemistry
Stability of the Nuclei
a. Elements with atomic number 84 and above
b. Proton to neutron ratio
Common forms of radiation-Table O
Nuclear equations
a. Be able to balance
Fission
Fusion
Artificial vs. Natural Transmutation
Half-life
a. Be able to solve problems
Uses and Dangers of Radioisotopes
a. Dating
b. Chemical tracers
c. Industrial applications
d. Medical Applications
9. Radiation Risks

3. Most chemical reactions involve either the exchange or sharing of
Nuclear Chemistry
Most chemical reactions involve either the exchange or sharing of
electrons between atoms. Nuclear chemistry is quite different in
nature because it involves changes in the nucleus.
When the atomic nucleus of one element is changed into the
nucleus of a different element, the reaction is called a transmutation
Most nuclei are stable, that is, they are found within the
“belt of stability.” It is the ratio of neutrons to protons that
determines the stability of a given nucleus.
Elements with atomic number 84 and above, have no stable
isotopes (radioisotopes).

4. Zone of Stability
Plot of proton to neutron ratio
showing the stable isotopes
If the proton to neutron ratio of an
atom falls outside of the zone of
stability, it is an unstable isotope

5. Common Forms of Radiation
Table O

6. Marie Curie
November 7, 1867-July 4, 1934
First woman to win a Nobel Prize, the only woman to win in two fields and the only person to win in multiple sciences.
Because of their levels of radioactivity, her papers from the 1890s
are considered too dangerous to handle. Even her cookbook is
highly radioactive. Her papers are kept in lead-lined boxes, and
those who wish to consult them must wear protective clothing.

7. Notice gamma radiation has no mass and no charge.
Mass number
4He 2
charge
Notice gamma radiation has no mass and no charge.
It is NOT a particle but instead it is a ray.
The alpha particle is a helium nucleus
The beta particle is an electron

8. Name
Penetrating Power
Ionizing Power
Alpha
Weak
Strong
Beta
Average
Gamma
Because gamma has the greatest penetrating power, it is the
type of radiation that is most dangerous to humans.
Ionizing power is the ability of radiation to knock electrons off
some atoms of the bombarded substance to produce ions.

9. Anything that is radioactive may give off alpha or beta particles.
Anything radioactive will always give off gamma radiation.
Therefore, anything radioactive is dangerous to humans.

10. Why does the beta particle deflect to the + side of the electric field?
Beta has a – charge and is attracted to the + electric field
Why does the alpha particle deflect to the – side of the electric field?
Alpha has a + charge is attracted to the – electric field
Why does the gamma ray pass through undeflected?
Gamma has no charge and is unaffected by the field
Opposite charges attract

11. When an unstable nucleus emits an alpha particle, the nucleus
Alpha Decay
When an unstable nucleus emits an alpha particle, the nucleus
is called an alpha emitter.
Alpha decay can be summarized as follows:
1. Atomic number decreases by two
2. Number of protons (charge) decreases by two
3. Number of neutrons decreases by two
4. Mass number decreases by four
Mass #
(p + n)
226Ra  222Rn + 4He 86 2 88
# protons (charge)

12. disintegration is said to undergo beta decay and is called a
A nucleus that emits a beta particle as a result of a nuclear
disintegration is said to undergo beta decay and is called a
beta emitter
Beta decay can be summarized as follows:
1. Atomic number increases by one
2. Number of protons increases by one
3. Number of neutrons decreases by one
4. Mass number remains the same
Mass # (p + n)
214Pb  214Bi + 0e 82 83 -1
# protons (charge)

13. One of the things you must be able to do is balance a nuclear
equation. It must be balanced in terms of mass, charge and energy.
The mass numbers on both sides of the equation add up to 18 18 18
14N + 4He  17O + 1H 7 2 8 1 9 9
The atomic numbers (charges) on both sides of the equation add
up to 9

14. Lets try some: 1. 27Al + 1n  24Na + X X = 4He 13 11 X = 14N
X = 14N
2. 14C  X + 0e 6 -1 7
3. 12C + 249Cf  257Rf + 4X
X= 1n 6 98
104

15. Fission Reactions
A fission reaction begins with the capture of a neutron by the
nucleus of a heavy element. The nucleus produced by the capture
is unstable. It immediately splits, undergoing the process of fission.
1n + 235U  142Ba + 91Kr + 31n + energy 92 56 36
The products of fission are radioactive and must be safely stored until they become stable. This presents a huge problem since some of these products are radioactive for thousands of years.
We harness the energy produced and use it for turning the turbines to generate electricity or for use in nuclear weapons

16. Fusion Reactions
Involve the combining of light nuclei to form heavier ones
1H + 1H  2H + 0e 1 1 1 +1
1H + 2H  3He 1 1 2
3He + 3He  4He + 21H 2 2 2 1
3He + 1H 4He + 0e 2 1 2 +1
While these reactions produce the energy from the sun, they are
not yet available to produce energy here on Earth. Extremely
high temperatures and pressure are needed to allow the positively
charged hydrogen nuclei to fuse into helium.
Remember the nuclei are positively charged and repel each other
and resist being fused together

17. This loss of mass seems to contradict our concept that matter
Fission and Fusion
In both types of reactions, the total mass of the products is less than the total nuclear mass of the reactants
This loss of mass seems to contradict our concept that matter
(mass) can neither be created or destroyed. The loss of mass in
these nuclear reactions represents a conversion of some matter
into a large amount of energy.
This relationship was expressed by Albert Einstein in his
famous equation:
E = mc2
A minute amount of matter produces an extremely large amount
of energy

18. Particle Accelerators
Accelerate the speed/velocity of particles by using electrical and magnetic fields.
Neutrons cannot be accelerated by particle accelerators because they are neutral and cannot be affected by these fields

19. Transmutations
Nuclear reactions can be either naturally occurring or artificial.
Natural transmutation-
Occur by radioactive decay
18F  17O + 1H 9 8 1
Notice that the element changed without us having to do anything
to it
Artificial transmutation-
Occur when particles bombard the
nucleus of the atom
9Be + 4He  12C + 1n 4 2 6
Notice that the element has to be bombarded with a particle
before it will change

20. Half-Life
Radioactive substances decay at a constant rate that is not
dependent on factors such as temperature, pressure or
concentration. It is also a random event. It is impossible to
predict when a given unstable nucleus will decay. However, the
number of unstable nuclei that will decay in a given time in a
sample of the element can be predicted.
The time it takes for half of the atoms in a given sample of an
element to decay is called the half-life of the element.

21. Table N gives you the half-life of selected radioisotopes and also
gives you the decay mode of these
radioisotopes also

22. Notice that after each half-life, half of the radioactive
sample remains

23. Most chromium atoms are stable, but Cr-51 is an unstable
isotope with a half-life of 28 days.
a. What fraction of a sample of Cr-51 will remain after
168 days? 28 56
112
140
168 84
1/1
1/2
1/4
1/8
1/16
1/32
1/64
If a sample of Cr-51 has an original mass of 52 g, what
mass will remain after 168 days? 28
168 56 84
112
140 52 26 13
6.5
3.25
1.63
.813

24. How much was present originally in a sample of Cr-51 if 0.75 mg
remains after 168 days?
112
140
168 28 56 84 ?
24.0
12.0
6.0
3.0
1.5
.75
48 mg

25. In 6. 20 hours, a 200 g sample of Ag-112 decays to 50 g
In 6.20 hours, a 200 g sample of Ag-112 decays to 50 g. What is the half-life of Ag-112?
6.20 h
200
100 50
It underwent 2 half –lives (2 arrows), so we divide 6.20 by 2
6.20/2 = 3.10 hours
Half-life of Ag-112 is 3.10 hours

26. Uses and Dangers of Radioisotopes
Radioisotopes have many practical applications in industry,
medicine and research. They also have potential dangers
because of harm that could be done by the radiation released.
1. Dating
C-14 decays to form stable C-12 is used to date living or
once alive materials
U-238 decays to form stable Pb-206 and is used to date
geologic formations

27. 2. Chemical Tracers
Any radioisotope used to follow the path of a material in a system
If P-31 is present in fertilizer administered to a plant, the uptake
of the radioactive phosphorus can be traced by detectors.
Scientists can then determine the proper amounts and timing of
fertilizer applications.

28. I-131-uses in both the detection and treatment of thyroid conditions
3. Medical Applications
Certain radioisotopes that are quickly eliminated from the body and have short half-lives are important as tracers in medical diagnosis
I-131-uses in both the detection and treatment of thyroid conditions
Co-60-aimed at cancerous tumors and kills cells of tumor
Some radioisotopes are used to irradiate food and kill bacteria.
The food lasts longer without spoiling and causes fewer bacterial
Infections in those who consume it
Tc-99-absorbed by cancerous cells and is easily detected by a scan.

29. Radiation Risks
1. Kill cancerous cells but have the potential to damage normal cells
2. High doses of radiation can cause serious illness and death
Radiation can cause mutations in sex cells that could
potentially be passed from generation to generation
Nuclear power plants have waste products with long half-lives
which make them difficult to store and dispose of