1. Nuclear Chemistry
Throughout history people have tried to control the chemical matter in their world. In order to do so, an understanding of the nature of matter; its inner-workings is of course necessary.

2. Nuclear Chemistry
The ultimate goal of changing lead to gold, as was the alchemists’ ambition was never reached.
An understanding of the world of the nucleus is necessary, and we are still engaged in that endeavor to this day.

3. Changes: physical H2O(s)  H2O(l)
To understand the nucleus and its changes it is necessary to review physical and chemical changes.
In physical changes such as melting or boiling, the structure of the molecules themselves does not the change. As a result the chemical formula remains the same, and in general only gross physical properties change.
Scientist agree:
Climate change happens!
Polar bears depend on ocean ice to hunt seals. Polar bears may be extinct within our lifetime
H2O(s)  H2O(l)

4. Changes: physical H2O(s)  H2O(l)
Illustrate the melting of ice with a particle diagram:
Scientists agree;
climate change happens!
H2O(s)  H2O(l)

5. Physical Changes Ex: H2O (s) + energy  H2O (l)
>Molecules arrangement with each other changes
>The physical properties change
The crystal structure of ice breaks down, but its still H2O!
>The chemical formula
and the composition
remains unchanged
>Small energy
changes occur
Examples: Melting, dissolving ,etc.

6. Changes: chemical H2 + O2  H2O
In chemical changes the molecular structure itself is changed as the atoms rearrange into new combinations. As a result new molecules are formed, with a completely different chemical formula and a host of new properties, depending on the new arrangement of atoms.
H2 + O2  H2O

7. Changes: chemical H2 + O2  H2O
This type of change may or may not involve a transfer of electrons between the atoms involved, leading to a more stable arrangement of electrons.
Do you recall that atoms lose or gain electrons typically to become like noble gases?
H2 + O2  H2O

8. Changes: chemical H2 + O2  H2O H2 + O2 H2O
Illustrate the reaction of hydrogen with oxygen to form water using a particle diagram: H’s O’s
H2 + O2  H2O
H2 + O2 H2O
Be sure to apply the law of conservation of mass

9. Chemical changes Ex: H2 + O2  H2O + energy
>Atoms in the molecule rearrange
>A new substance formed
>A new chemical formula
and different composition
Happy
new molecules
of H2O!
>The physical AND chemical properties change
>Larger energy changes are involved
Examples: rusting, burning, etc.

10. So it is that in neither physical nor chemical changes, has the nucleus’ arrangement of neutrons and protons changed. The nucleus in a sense is like the world of Dr. Seuss and the whos. It’s a place unaffected by outside factors like temperature and pressure.

11. The nucleus is as unaware of the changes that occur in the chemical world outside, as we are of the changes that occur within. It is a world governed by unimaginably strong forces, the likes of which we’ve only just begun to understand.
Welcome to the strange world of nuclear chemistry

12. 1 - Nuclear Changes > Nuclear particles rearrange
Watch carefully below
Can you spot a neutron changing into a proton?
In the example, an unstable carbon 14 nucleus changes into a stable Nitrogen 14 nucleus.

13. Nuclear Changes > Nuclear particles rearrange
As nuclear particles rearrange radiation particles are given off. In this case a beta particle is released.

14. Nuclear Changes > Nuclear particles rearrange
Changes such as this nuclear decay, involve nuclear particles changing forms:
In this case neutrons are changing into protons.

15. Nuclear Changes
> Nuclear particles rearrange
> Atomic number can change
and Old elements can change
into new elements
When the number of protons change the atomic number and identity of the element change

16. Nuclear Changes
> Nuclear particles rearrange
> Atomic number can change
and Old elements can change
into new elements
>Mass is converted into energy
(as Radiation)
The radiation that is given off comes when matter is converted into energy. The famous E=mc2 equation of Einstein shows the relationship

17. Nuclear Changes
> Nuclear particles rearrange
> Atomic number can change
and Old elements can change
into new elements
> Mass is converted into energy
(as Radiation)
> Largest energy changes
Nuclear reactions like this fusion explosion release much more energy than even the most violent of chemical changes.

18. Nuclear Changes > Nuclear particles rearrange
> Atomic number can change
and Old elements can change
into new elements
>Mass is converted into energy
(as Radiation)
> Largest energy changes
A more useful nuclear change is fission, which can provide huge amounts of electricity and doesn’t contribute to climate change.

19. Nuclear Changes > Nuclear particles rearrange
> Atomic number can change
and Old elements can change
into new elements
> Mass is converted into energy
(as Radiation)
> Largest energy changes
Examples: radioactive decay, fission, fusion
It has other undesirable consequences though.

20. Nuclear Stability
> Stability of the nucleus depends on ratio between protons and neutrons
> Stable ratio is fairly equal
> (1proton :1neutron) in smaller atoms,
> About 1 : 1.3 ratio in larger atoms
Ex: Bromine 80 = 35 protons : 45 neutrons

21. Nuclear Stability Ex: Carbon 12 Ex: Carbon 14 6 protons 6 protons
6 neutrons
Stable nucleus
Ex: Carbon 14
6 protons
8 neutrons
Unstable nucleus
Think of the nucleus like a blob of cookie dough. Not enough water and dough crumbles, too much water and its too runny to stay together. The nucleus requires a particular ratio of protons to neutrons to be a stable unit.

22. The graphic below shows the numbers of neutrons and protons for specific nuclides or C, N, Ne, and S
Explain, in terms of atomic particles why the S-32 shown in the graph is stable

23. Radioactivity: 1) Transmutation or “decay”
Many different kinds of radiation
Particles can be produced
Transmutation also known as “decay” occurs when particles in an unstable nucleus break down releasing a particle of radiation.

24. Radioactivity: Transmutation or “decay”
Many different kinds of radiation
Particles can be produced
> All atoms above atomic number 84 have an unstable nucleus. In the illustration an unstable Uranium nucleus decays, releasing a particle of radiation,

25. Radioactivity: Transmutation or “decay”
Many different kinds of radiation
Particles can be produced
Though Uranium releases neutrons, a variety particles of radiation are released by other elements. These include alpha particles, protons, and negative beta particles (like electrons from the nucleus!).
Pure energy can also be released in the form of gamma radiation.

26. Particles: Reference table O:
Alpha particles – (alpha decay)
> Largest particle, with mass of 4
and +2 charge
>Similar to helium nucleus: 2 He 4
upper: Mass #
Lower: Atomic #
(“nuclear charge”)
>Greek symbol alpha α

27. Ex: Alpha emitter: Pu-234 94 Pu 240  92 U 236 + 2 He 4
particle
This is a nuclear equation. In nuclear equations, the atoms change, so an element present on one side, will be a different element on the other side.

28. Ex: Alpha emitter: Pu-234 94 Pu 240  92 U 236 + 2 He 4
particle
Notice though,how the atomic numbers (charge #) and mass numbers balance. More on this later!
Notice: unstable Plutonium loses 2 protons, becomes uranium

29. 6 C 14  7 N 14 + -1 e 0 Beta particles (Beta Decay)
>Small particles with little mass
and -1 charge
>Similar to electron -1 e 0
Notice the lower
Number is the charge
>Greek symbol β
Beta Emitter: Carbon 14
6 C 14  7 N e 0
Beta radiation
Notice: Carbon loses a negative charge and ends up with
an extra proton (Atomic number 6 changes to 7) How?
A neutron loses a negative charge and becomes a proton!

30. Gamma Radiation >Highest energy particle, similar to x -rays
>Has no apparent mass or charge (neutral)
>Symbol gamma: γ
No loss of charge or mass means element doesn’t change
(Though its usually given off with other particles)
Ex: Cobalt-60 emits gamma rays in addition to beta electrons

31. Selected Radioisotopes
Shown in Table N
(radioactive, unstable)
Radiation forms

32. Try this problem: (we’ll do more of these. Later)
What particle is represented by X?
C11  B11 + X
Solution: Insert atomic numbers (from per. Table)
and missing mass numbers to balance
C11  B X
0 mass and +1 charge? 6 5 +1
In nuclear equations numbers must balance on both sides.
+6 nuclear charge on the left. We insert a +1 on the right to balance.
The mass of 11 on the left balances with the 11 on the right.
The particle X must have a mass of zero.

33. C11  B11 + X C11  B11 + X 6 5 +1 According to table O
Try this problem: (we’ll do more of these. Later)
What particle is represented by X?
C11  B11 + X
Solution: Insert atomic numbers (from per. Table)
and missing mass numbers to balance
C11  B X
0 mass and +1 charge? 6 5 +1
According to table O
It’s a positron
Anti-matter!
Produced in particle accelerator

34. Try one: But don’t peek! Notice:
U-238’s mass decreases by 4, nuclear charge decreases by 2: Loss of alpha particle +2He4
2) Th234’s mass stays same, 0 mass lost, but nuclear charge increases by +1: loss of -1 charge: -1e0 beta particles.
3) Same change for Pa-234 turning into U-234

35. Penetration of particles
>Alpha’s are the largest (mass of 4), so they penetrate little
>Beta’s are smaller, (mass of 0, like an electron) penetrate easier
>Gamma’s smallest (pure energy), highest penetration
What stops the radiation?
Keep and eye peeled
for this paper, wood,
and concrete example

36. Indian point nuclear power plant in Peekskill
What are the silos made from? Why?

37. Separation of particles
>Alpha’s are positive, deflected toward negative plate
>Beta’s are negative, deflect toward positive side
>Gamma’s are neutral, undeflected.
This website shows animates the separation of particles
Can you tell which particle is which?

38. Test your learning
How are physical changes different from chemical changes? How does the nucleus change during those changes?
What are the main characteristics of nuclear changes?
What characteristic of an atom’s nucleus causes it to be unstable?
What are the three naturally produced radiation forms? What are their properties?

39. Click here to check out the crash course take on this topic

40. The energy released by a nuclear reaction results primarily from the
(1) breaking of bonds between atoms
(2) formation of bonds between atoms
(3) conversion of mass into energy
(4) conversion of energy into mass
The stability of an isotope is based on its
(1) number of neutrons, only
(2) number of protons, only
(3) ratio of neutrons to protons
(4) ratio of electrons to protons
Which of these types of radiation has the greatest penetrating power?
(1) alpha (3) gamma
(2) beta (4) positron

42. 2- Half-life +1600= +1600= >Radioisotopes decay at a special rate
>Used to age geologic and fossil samples
Example: (Ref Table H)
Radium 226 Half-Life = 1600 years
After Time
# half-lives
% sample remaining
Fraction remaining
Mass remaining
100
all
10.00 g
½ left
after1600 y
After 1 half-life
50% of original
5.00 g left
+1600=
¼ left
after 3200 y
After 2 half-life
25% of original
2.50 g left
+1600=
after 4800 y
After 3 half-life
1/8 left
1.25 g left
12.5% of original
Suppose that we start with 10 grams of Ra-222

43. Half-life time is listed on reference table N
Carbon-14’s ½ life is 5,700 years
Uranium-238’s ½ life is 4.5 billion years
Which would work better to find the age of ancient rocks? (hint: the earth is billions of years old!)
Answer: U-238. half–life closer to target age.

44. Graphing radioactive decay
Starting
mass.
After one
Half-life.
What fraction is left after the second half-life?
Question: According to the graph, What is the half-life of Cesium 137?
Original sample is 100 grams, drops to 50 grams after 30 years.

45. (Number of half-lives)
Fraction remaining problems
Ex: What fraction of a sample of K-42
remains unchanged after 49.6 hours?
Ref. Table N: Half life K-42 = 12.4 hrs
Total time
Half-life time
49.6 hrs
12.4 hrs =
4 half-lives
Fraction Remaining = (1/2)
= (1/2) 4
(Number of half-lives)
= ½ x ½ x ½ x ½
= 1/16th

46. = ½ x ½ x ½ x ½ x ½ fraction remaining = (1/2)36/7.2 (1/2)5
Or make a table:
time
fraction
all
7.2 sec
1/2
14.4 sec
1/4
21.6 sec
1/8
28.8 sec
1/16
36.0 sec
1/32
fraction remaining =
(1/2)36/7.2
= ½ x ½ x ½ x ½ x ½
(1/2)5

47. Here’s another:
Based on the selected radioisotopes chemistry reference table, what is the fraction of a sample of potasium-42 that will remain unchanged after 62.0 hours?
time
fraction
all
12.4 hrs
1/2
24.8 hrs
1/4
37.2 hrs
1/8
49.6 hrs
1/16
62.0 hrs
1/32

48. Nuclear Equations 90Th 234 Ex: 92 U 238  + 2 He 4 Notice: Mass
238 = Mass is conserved
Notice:
90Th 234
Ex: 92 U 238 
+ 2 He 4
Mass
Nuclear charge
Notice:
92 = charge is conserved

49. What is the identity of X?
Nuclear equations can be balanced just like chemical equations. The problem below illustrates the process.
Problem:
What is the identity of X?
= ?
Ex: 88 Ra 226  X He 4
= ?
86X 222
Atomic number 86 = Radon
86Rn 222

50. Test your learning
The half life of iodine-125 is 60 days. What fraction of iodine-125 nuclides would be left after 360 days?
A medical institution requests 1 g of bismuth-214, which has a half life of 20 min. How many grams of bismuth-214 must be prepared if the shipping time is 2 h?
Use reference table to write the nuclear equation for the decay of iodine 131. What particle is emitted? What new element is produced?
Radon 222 is produced by the decay of what radioisotope? Write a balanced nuclear equation to find out:

51. +1
A positron

52. Regents exam question 79 - 81:

55. 3 - Radioactivity: Artificial Transmutation
>Decay caused by bombarding nuclei with outside radiation, in particle accelerators
Ex: Al He 4  P n 1
And
more
Radiation
(a neutron)
element
Hit with radiation
Forms New element
(an Alpha particle)
In artificial transmutation, look for a radiation particle
on the left, reactant side. Particles to look for include
Protons or the like: 1 H 1 and Alpha particles: 2 He 4

56. Particle accelerators are used study
the structure the atom’s nucleus

57. > Particles are accelerated to a high speeds
And then collide into various samples.
Detectors help analyze the results.
This website is the particle adventure. What are subatomic particles made of?

58. The strange world of sub-subatomic particles
Aka: What are Protons, neutrons and electrons made of?
(not on the regents exam, but who cares? Its weird, cool stuff!)
Elementary particles: Quarks (nuclear),
leptons (electron) & gluons (force carriers)
6 Quark flavors:
up(+2/3 charge)
down (-1/3)
charm (+2/3)
strange (-1/3)
top (+2/3)
bottom (-1/3)
proton
u(+2/3 )
+ d(-1/3 )
+ 1
Neutron
u(+2/3 )
d(-1/3 )
+ d(-1/3 )
FYI: particleadventure.org

59. 2-4 aren’t even nuclear changes,
they’re chemical reactions!
An easy one, huh?

60. Radioactivity: Nuclear Fission
Fission = Splitting the atom’s nucleus
Releases large amounts of energy

61. Nuclear Fission > A large nucleus is split into two smaller nuclei
More
Radiation
radiation
Releases
energy
U fuel
2 products

62. Chain Reaction 1  3  9  27  etc.
In a chain reaction, on neutron strikes a nucleus, splitting it and releasing 3 neutrons. Each of the 3 strikes another nucleus, releasing a total of 9 neutrons. And so on. Imagine the consequences!
Chain Reaction
1  3  9  27  etc.

65. Mass is converted into energy
during nuclear changes

67. Left over Nuclear waste must be stored.
How nuclear power plants work
Left over Nuclear waste must be stored.
Bad!
Radiation
Released
In the reactor
Heats up
a fluid
Electricity is passed along the grid to our homes and businesses
Heat is passed to water changing it to steam
Steam under pressure drives
A generator (turbine) to make electricity
steam condenses back giving up its heat passed back to a nearby river

68. Nuclear Energy Advantages
>No gas emissions like with fossil fuels (leading to climate change)
>Lots of energy for small amount of fuel
Disadvantages
>Radioactive waste has long half-lives
Remain dangerous for long periods
Present long term storage problems

69. Nuclear Fusion >Fusion = put together
>Two small nuclei combine into one
>Release huge amounts of energy
1 H H 3  2 He n 1 + energy
deuterium and tritium
changed into
Helium
Problem: Positive nuclei repel
must use small nuclei used to overcome forces
Extremely High temperatures required

71. Nuclear weapons: the H bomb
Aka: what good is a device that destroys everything?
TNT chemical bomb  fission bomb  fusion bomb

72. Test your learning
Write a nuclear equation showing natural transmutation and an equation showing artificial transmutation. Explain how they are different.
Describe one advantage of nuclear fission and one disadvantage.
What advantage does nuclear fusion have over nuclear fission? Why don’t we use nuclear fusion for energy production?

74. Can you identify these changes?
Fission
Natural Transmutation (alpha decay)
Artificial Transmutation
Fusion
synthesis
decompostion
Artificial Transmutation
Natural Transmutation
(beta decay)

75. 4 - Uses for Radioisotopes
Tracers – track chemical reactions
Ex: Photosynthesis with radioactive Oxygen tracer
CO2 + H2O + sunlight  C6H12O6 + O2
Where does the Oxygen we breath come from?
Notice where the O in O2 came from?
From the water! (not the CO2)
Industrial applications
Measuring thickness of material,
based on absorption of radiation
(thicker materials absorb more radiation)

76. Uses for Radioisotopes
Medical Treatments (short half-lives)
Technetium 99
– Diagnose brain tumors (tracer)
Iodine 131
– Treat thyroid disorders
Radium and Cobalt 60
– cancer treatment

77. Half-life determines its application
Food Irradiation
kills bacteria and fungi, prevents food spoilage
Geologic dating
U-238 to Pb-206 ratio – dating rocks
C-14 to N-14 ratio – age of fossils
Half-life determines its application

78. Test your learning
What characteristic of a radioisotope is important for its use in medical procedures?
What advantage does irradiated food have for developing countries?
What radiation particle is emitted by Technetium 99, allowing it be visible during a bone scan?
Why is uranium 238 used to date rock formations while Carbon 14 is used for fossils?