1. Nuclear Chemistry

2. 23.1

3. Nuclear Reactions vs. Normal Chemical Changes
Nuclear reactions involve the nucleus
The nucleus opens, and protons and neutrons are rearranged
The opening of the nucleus releases a tremendous amount of energy that holds the nucleus together – called binding energy
“Normal” Chemical Reactions involve electrons, not protons and neutrons

4. A. Wilhem Rontgen - discovered x-rays in 1895
I. Nuclear Chemistry
A. Wilhem Rontgen - discovered x-rays in 1895
B. Antoine Henri Becquerl - discovered radioactivity
1. photographic plates and rocks
C. Marie and Pierre Curie - discovered other
radioactive elements
1. Marie first person to win the Nobel peace prize
twice

5. 3. Marie and her children died of radiation poisoning
2. husband run over by wagon when he was crossing
the street
3. Marie and her children died of radiation poisoning

6. Radioactivity
One of the pieces of evidence for the fact that atoms are made of smaller particles came from the work of Marie Curie ( ).
She discovered radioactivity, the spontaneous disintegration of some elements into smaller pieces.

7. A. Spontaneous break down of an unstable nucleus
II. Radioactivity
A. Spontaneous break down of an unstable nucleus
with the release of particles and rays
B. Mass defect and nuclear stability
1. the sum of the particles(protons, neutrons
and electrons) that make up an atom but does
not add up to the mass of an atom
2. the difference between the sum of the masses
and the atomic mass is know as the
mass defect

8. Mass Defect Some of the mass can be converted into energy
Shown by a very famous equation!
E=mc2
Energy
Mass
Speed of light

9. C. Nuclear binding energy
1. The energy released when a nucleus is formed
from nucleons (protons and neutrons)

10. III Properties of Radioactive elements
1. They affect photographic film
2. They produce electric charges in the
surrounding air
3. They produce fluorescence with certain
compounds
a. fluorescence - makes thing glow

11. 4. Their radiation’s have special physiological effects
a. causes mutations in cells - changes in the
DNA of cells causing rapid growth and a
change in their function
5. They undergo radioactive decay
a. Radioactive decay - they emit particles from
the nucleus making simpler atoms
i. half-life - the time it takes 1/2 a given
amount to decay
ii. Half-lives can be from a few seconds
to millions of years

12. Half-Life
HALF-LIFE is the time that it takes for 1/2 a sample to decompose.
The rate of a nuclear transformation depends only on the “reactant” concentration.

13. Kinetics of Radioactive Decay
For each duration (half-life), one half of the substance decomposes.
For example: Ra-234 has a half-life of 3.6 days If you start with 50 grams of Ra-234
After 3.6 days > 25 grams
After 7.2 days > 12.5 grams
After 10.8 days > 6.25 grams

14. Half-Life
Decay of 20.0 mg of 15O. What remains after 3 half-lives? After 5 half-lives?

15. e.g. The half-life of Plutonium -239 is 24110 years.
Of an original mass of 100. g, how much remains after
96440 years
first find the number of half-life's
# Half-lifes = years
24110 Years
= 4
now divide the gram sample in 1/2 four times
100
===> 50
===> 25
===>12.5
===> 4 1 2 3

16. The half-life of thorium -227 is 18.72 days. How many
days are required for 3/4 of a given amount to decay
18.72 days
18.72 days
1 ===> 1/2 ===> 1/4
This tells you that you have 1/4 of the original amount left
- therefore - 3/4 of a given amount has decayed
you must multiply days by 2 == days

17. e.g Exactly 1/16 of a given amount of protactinium-234
remains after hours. What is the half-life of
protactinium - 234
First find the number of half-life's
1 ==> 1/2 ===> 1/4 ===> 1/8 ===> 1/16
You must pass threw 4 half life’s
26.76 hours
4 half-life’s
= 6.69 hours/half-life

18. The half life of I-123 is 13 hr. How much of a 64 mg sample of I-123 is left after 78 hours?

19. Nuclear Stability
Certain numbers of neutrons and protons are extra stable
n or p = 2, 8, 20, 50, 82 and 126
Like extra stable numbers of electrons in noble gases (e- = 2, 10, 18, 36, 54 and 86)
Nuclei with even numbers of both protons and neutrons are more stable than those with odd numbers of neutron and protons
All isotopes of the elements with atomic numbers higher than 83 are radioactive
All isotopes of Tc and Pm are radioactive
23.2

20. Band of Stability and Radioactive Decay
When the number
of protons in a stable
nuclei is plotted
against the
number of neutrons
Band of Stability and Radioactive Decay

21. Stability of Nuclei Out of > 300 stable isotopes: N Even Odd Z 15752
3115P
Even
Odd 50 5
21H, 63Li, 105B, 147N, 18073Ta
199F

22. a. alpha particles, a, contain two protons and
Radioactive decay
1. types of particles
a. alpha particles, a, contain two protons and
two neutrons - can be stopped by a piece of
paper - have low penetrating power - may
cause burns to the flesh
b. beta particles, b, high speed electrons, travel
at close to the speed of light, c, which is
equal to 3 x 108 m/sec or 186,000 miles a sec
c. gamma rays, g, are high energy electromagnetic
waves. Most penetrating

23. Types of Radiation Beta – an electron
Alpha – a positively charged (+2) helium isotope - we usually ignore the charge because it involves electrons, not protons and neutrons
Beta – an electron
Gamma – pure energy; called a ray rather than a particle

24. Other Nuclear Particles
Neutron
Positron – a positive electron
Proton – usually referred to as hydrogen-1
Any other elemental isotope

25. Penetrating Ability

26. X Atomic number (Z) = number of protons in nucleus
Mass number (A) = number of protons + number of neutrons
= atomic number (Z) + number of neutrons
Mass Number X A Z
Element Symbol
Atomic Number 1p 1 1H or
proton 1n
neutron 0e -1 0b or
electron 0e +1 0b or
positron
4He 2 4a or
a particle A 1 1 4 Z 1 -1 +1 2
23.1

27. 3. radioactive decay sequence
238U > a Th90
daughter
parent
when you have an alpha ejection - you lose 2
protons and 2 neutron
The 92 of uranium is the number of protons and will go to 90
with an alpha ejection - the number of protons in you
nucleus determines the element.

29. therefore - U turns into Th
The 238 of U is the total number of particles in
the nucleus = number of protons and neutrons -
with an alpha ejection - you lose 2 protons and 2
neutrons your mass goes down by 4 or become 234
226Ra > a Rn86

30. 234Pa91 ----> 234U92 + beta particle
When you have a beta ejection - you have a neutron
change to a protons thus causing your number of protons to
go up by one. The total number of particles in the nucleus
does not change
234Pa > 234U92 + beta particle
234Th >234Pa91 + b

32. On page 724 do problems 33,34,35,40,41,42,43

33. 212Po decays by alpha emission
212Po decays by alpha emission. Write the balanced nuclear equation for the decay of 212Po.
4He 2 4a or
alpha particle -
212Po He + AX 84 2 Z
212 = 4 + A
A = 208
84 = 2 + Z
Z = 82
212Po He + 208Pb 84 2 82
23.1

34. Nuclear Stability and Radioactive Decay
Beta decay
14C N + 0b + n 6 7 -1
Decrease # of neutrons by 1
40K Ca + 0b + n 19 20 -1
Increase # of protons by 1
1n p + 0b + n 1 -1
Positron decay
11C B + 0b + n 6 5 +1
Increase # of neutrons by 1
38K Ar + 0b + n 19 18 +1
Decrease # of protons by 1
1p n + 0b + n 1 +1
n and n have A = 0 and Z = 0
23.2

35. Nuclear Stability and Radioactive Decay
Electron capture decay
37Ar + 0e Cl + n 18 17 -1
Increase # of neutrons by 1
55Fe + 0e Mn + n 26 25 -1
Decrease # of protons by 1
1p + 0e n + n 1 -1
Alpha decay
Decrease # of neutrons by 2
212Po He + 208Pb 84 2 82
Decrease # of protons by 2
Spontaneous fission
252Cf In + 21n 98 49
23.2

36. What radioactive isotope is produced in the following bombardment of boron?
10B He ? n

37. What radioactive isotope is produced in the following bombardment of boron?
10B He N n

38. Write Nuclear Equations!
Write the nuclear equation for the beta emitter Co-60.
60Co 0e + 60Ni

39. Positron emission -conversion of a proton to a neutron by
the emission of a positron
1. Positron - particle that has the same mass as an
electron, but has a positive charge
Gamma radiation - does not change the identity of the
element but makes the atom more stable
Transmutation - changing the identity of an element through
the release of radioactive particles
Isotopes - atoms of the same element that have different
number of neutrons

40. Geiger-Müller Counter
23.7

41. Geiger Counter
Used to detect radioactive substances

42. Artificial Nuclear Reactions
New elements or new isotopes of known elements are produced by bombarding an atom with a subatomic particle such as a proton or neutron -- or even a much heavier particle such as 4He and 11B.
Reactions using neutrons are called g reactions because a g ray is usually emitted.
Radioisotopes used in medicine are often made by g reactions.

43. Artificial Nuclear Reactions
Example of a g reaction is production of radioactive 31P for use in studies of P uptake in the body.
3115P n ---> 3215P + g

44. Transuranium Elements
Elements beyond 92 (transuranium) made starting with an g reaction
23892U n ---> U + g
23992U > Np b
23993Np ---> Pu b

45. Biological Effects of Radiation
Radiation absorbed dose (rad)
1 rad = 1 x 10-5 J/g of material
Roentgen equivalent for man (rem)
1 rem = 1 rad x Q
Quality Factor
g-ray = 1
b = 1
a = 20
23.8

46. Effects of Radiation

47. Nuclear Fission Fission is the splitting of atoms
These are usually very large, so that they are not as stable
Fission chain has three general steps:
1. Initiation. Reaction of a single atom starts the chain (e.g., 235U + neutron)
2. Propagation. 236U fission releases neutrons that initiate other fissions
3. Termination.

48. Nuclear Fission

49. Nuclear Fission 235U + 1n 90Sr + 143Xe + 31n + Energy92 54 38
Energy = 3.3 x 10-11J per 235U
= 2.0 x 1013 J per mole 235U
= 235 grams
= 0.5 lbs
Combustion of 1 ton of coal = 5 x 107 J
23.5

50. Representation of a fission process.

51. Nuclear Fission
Nuclear chain reaction is a self-sustaining sequence of nuclear fission reactions.
The minimum mass of fissionable material required to generate a self-sustaining nuclear chain reaction is the critical mass.
Non-critical
Critical
23.5

52. Nuclear Fission & POWER
Currently about 103 nuclear power plants in the U.S. and about 435 worldwide.
17% of the world’s energy comes from nuclear.

53. Diagram of a nuclear power plant

54. Annual Waste Production
Nuclear Fission
35,000 tons SO2
4.5 x 106 tons CO2
1,000 MW coal-fired
power plant
3.5 x 106
ft3 ash
Annual Waste Production
1,000 MW nuclear
power plant
70 ft3 vitrified waste
23.5

55. Fusion Nuclear Fusion small nuclei combine 2H + 3H 4He + 1n + 1 1 2 0
Occurs in the sun and other stars
Energy

56. Nuclear Fusion
Fusion
Excessive heat can not be contained
Attempts at “cold” fusion have FAILED.
“Hot” fusion is difficult to contain

57. Radioisotopes in Medicine
1 out of every 3 hospital patients will undergo a nuclear medicine procedure
24Na, t½ = 14.8 hr, b emitter, blood-flow tracer
131I, t½ = 14.8 hr, b emitter, thyroid gland activity
123I, t½ = 13.3 hr, g-ray emitter, brain imaging
18F, t½ = 1.8 hr, b+ emitter, positron emission tomography
99mTc, t½ = 6 hr, g-ray emitter, imaging agent
Brain images with 123I-labeled compound
23.7

58. protection from radiation
A. Shielding
sunscreen, lead apron
B. distance
- inverse square law

62. Nagasaki Japan
August 9, 1945

63. Nuclear review You have a review test
A radioactive atom will lose the greatest amount of mass
when it emits
1. a neutron' 3.a beta particle ,
2. a proton 4.an alpha particle
A sample of iodine-131 contains 10. grams.
Approximately how much iodine-131 will remain after 24 days
(half life -8 days)?
g g
g g
3. What is the moderator in a nuclear reactor?
1. carbon dioxide 3. cadmium
2. boron graphite

64. 4. In the reaction 90Th234 -> 91Pa234 + X, X represents
1.a neutron 3. an alpha particle
2.a positron 4. a beta particle
5. One of the biggest advantages of a fusion reactor is it
1. produces no radioactive wastes
2. is small in size
3. will never explode
4. has no reaction control problem
6. Which particle has the least mass?
1. alpha particle 2. proton 3. neutron 4. electron

65. 7. A neutron has approximately the same mass as
1. an alpha particle 3. an electron
2. a beta particle 4. a proton
8. When 88Ra226 emits an alpha particle, the resulting atom is
Rn 2 2 2
Rn 2 2 4
Ra 2 2 2
Ra 2 2 4
To make nuclear fission nuclear reactor more efficient, which
device is used to slow the speed of neutrons?
1. internal shield 2. external shield 3.control rod 4.moderator
10. If radioactive substance has a half-life of 9 days,
what fraction of its original mass would remain after 27 days?
1. 1/ / / /4

66. If iodine-131 undergoes beta decay, which symbol represents
11. Which reaction illustrates fusion?
H2 + 1 H2 ===> 2He4
2. on1 + 13A127 ==> 11Na He4
3. 13A He4 ===> 15P He4 + 0 n1
4. 7 N He4 ===> 1 H1 + 8O17
Control rods in nuclear reactors are commonly made of boron
and cadmium because these two elements have the ability to
1) absorb neutrons
2) emit neutrons
3) decrease the speed of neutrons
4) increase the speed of neutrons
If iodine-131 undergoes beta decay, which symbol represents
the resulting nucleus?
1. 52Te Xe I Sb1 27

67. 14. Which element is formed when 82Pb214 emits a beta particle?
Po Hg Bi Bi214
Radioactive changes differ from ordinary chemical changes
In that radioactive changes
1.are explosive 3.involve changes in the nucleus
2.absorb energy 4.release energy
16. In the reaction
4Be9 + X ----> 6 C n1 the X represents
1.an alpha particle 3.an electron
2.a beta particle 4.a proton

68. 18. Which nuclear equation represents beta decay?
1. 13A He4 --> 15P30 + on1
U > 90 Th He4
3. 6 C > 7 N e0
4. 18Ar eo --> 17Cl37
19. An atom of Ra226 decays to Rn222 by emitting
1.a proton 3. an alpha particle
2.an electron 4. a beta particle
20. Heavy water may be used in a nuclear reactor as a
1.moderator 3. shielding
2.fuel 4. control rod
When an atom emits a beta particle, the total number of
nucleons
1. decreases 2. increases 3. remains the same

69. 22. The radioactive particle or ray with the greatest penetrating
power is the
1.alpha particle 3.gamma ray
2.beta particle 4.proton
23. The major portion of an atom's mass consists of
1) electrons and protons 3) neutrons and positrons
2) electrons and neutrons 4) neutrons and protons
During a chain reaction the number of nuclei reacting
per second
1. increases decreases 3. remains the same

70. 25. A radioactive source emits radiation which is deflected as shown in the diagram. .
This radiation could be
1. _1eo
2. 2 He4
3. 1 H1
4. 0 n1

71. When 90Th234 emits a beta particle ( -1 e0), the element
formed is
1. Ra 2. Th 3. Pa 4. U
27. A 40.0 milligram sample of phosphorus -33 decays to
10.0 milligrams in 50.0 days. What is the half-life of
phosphorus-33?
days days
days days
28. During a fission reaction, which type of particle is captured
by a nucleus?
1.deuterium 3.neutron
2.electron proton
29.When two light nuclei combine into a heavier nucleus,
the process is called
1.fission 3.beta decay
2.fusion 4.nuclear disintegration

72. 30, An electron has a charge identical to that of
1. a neutron 3. an alpha particle
2.a proton 4. a beta particle
31. In the reaction 92U238 --> 90Th234 + X, X represents
1.a beta particle 3. a positron
2.a neutron 4. an alpha particle

73. Tokamak magnetic plasma confinement
Nuclear Fusion
Fusion Reaction
Energy Released
2H + 2H H + 1H 1
6.3 x J
2H + 3H He + 1n 1 2
2.8 x J
3.6 x J
6Li + 2H He 3 1 2
Tokamak magnetic plasma confinement
23.6

74. Balancing Nuclear Equations
Conserve mass number (A).
The sum of protons plus neutrons in the products must equal the sum of protons plus neutrons in the reactants. 1n U
235 92 + Cs
138 55 Rb 96 37
+ 2
= x1
Conserve atomic number (Z) or nuclear charge.
The sum of nuclear charges in the products must equal the sum of nuclear charges in the reactants. 1n U
235 92 + Cs
138 55 Rb 96 37
+ 2
= x0
23.1

75. Radiocarbon Dating 14N + 1n 14C + 1H 14C 14N + 0b + n t½ = 5730 years6
14C N + 0b + n 6 7 -1
t½ = 5730 years
Uranium-238 Dating
238U Pb + 8 4a + 6 0b 92 -1 82 2
t½ = 4.51 x 109 years
23.3