1. The Nucleus: A Chemist’s View
Chapter 21
The Nucleus:
A Chemist’s View

2. Chapter 21: The Nucleus: A Chemists View
21.1 Nuclear Stability and Radioactive Decay
21.2 The Kinetics of radioactive Decay
21.3 Nuclear Transformations
21.4 Detection and Uses of Radioactivity
21.5 Thermodynamic Stability
21.6 Nuclear Fission and Nuclear Fusion
21.7 Effects of Radiation

3. Subatomic particle tracks in a bubble charger at CERN, the European particle physics laboratory in Geneva, Switzerland.
Source: CERN, Geneva, Switzerland

4. Figure 21.1: Known nuclides

5. DISTRIBUTION OF STABLE NUCLIDES
Protons Neutrons Stable Nuclides %
Even Even
Even Odd
Odd Even
Odd Odd
Total =
279
99.9%
(like table 21.1 , P 980)

6. PROPERTIES OF FUNDAMENTAL PARTICLES
Particle Symbol Charge Mass
(x Coulombs) (x10-27kg)
Proton P
Neutron N
Electron e

7. NUCLEAR STABILITY Modes of Radioactive Decay
Alpha Decay - Heavy Isotopes - 42He+2-
Beta Decay - Neutron Rich Isotopes - e - -
Positron Emission -Proton Rich Isotopes -
Electron Capture - Proton Rich Isotopes
x - rays
Gamma-ray emission(  - Decay of nuclear
excited states
Spontaneous Fission - Very Heavy Isotopes

8. Comparison of Chemical and Nuclear Reactions
Chemical Reactions Nuclear Reactions
1. One substance is converted to Atoms of one element typically
another,but atoms never change change into atoms of another.
identity.
2. Orbital electrons are involved as Protons, neutrons, and other
bonds break and form; nuclear particles are involved; orbital
particles do not take part electrons take part.
3. Reactions are accompanied by Reactions are accompanied by
relatively small changes in energy relatively large changes in
and no measurable changes in mass. energy and often measurable
changes in mass.
4. Reaction rates are influenced by Reaction rates are affected by
temperature, concentration, number of nuclei, but not by
catalysts, and the nature of the temperature, catalysts, or the
chemical substance nature of the chemical substance.

9. Emission and Absorption of Light by Atoms
Nucleus of atom
Electron
Light Emission occurs when an
electron drops from a higher
energy level to a lower one.
Light Absorption by an
atom moves an electron
to a higher energy level.

10. Absorption and Emission of Light by The Nucleus
Excited state
Ground state
Protons and Neutrons in the nucleus are moved up to excited states
by the absorption of large amounts of energy, and they move from
excited states back to the ground states by the emission of large
amounts of energy! This energy is normally 106 times larger than
the energy emitted by electron transfers around atoms, and is in the
Gamma ray region of the electromagnetic spectrum.

11. Figure 12.1: Electromagnetic radiation has oscillating electric (E) and magnetic (H) fields in planes perpendicular to each other and to the direction of propagation.

12. Figure 12.2: The nature of waves

13. Figure 12.3: Classification of electromagnetic radiation

14. Figure 21.7: Schematic representation of a Geiger-Muller counter

15. Alpha Decay -Heavy Elements
238U Th +  + E
T1/ 2= 4.48 x 10 9 yrs
210Po Pb +  + E
T 1/ 2= 138 days
256Rf No +  + E
T1/ 2= 7 msec
241Am Np +  + E
T1/ 2= 433 days

16. Beta Decay - Electron Emission
N P+ +  + Energy
90Sr Y +  + Energy
T1/ 2= 30 yrs
14C N +  + Energy
T1/ 2= 5730 yrs
247Am Cm +  + Energy
T1/ 2= 22 min
131I Xe +  + Energy
T1/ 2 = 8 days

17. Electron Capture - Positron Emission
P+ + e n + Energy = Electron Capture
P n + e+ + Energy = Positron Emission
51Cr + e V + Energy
T1/2 = 28 days
7Be Li +  + Energy
T1/2 = 53 days
177Pt + e Ir + Energy
T1/2 = 11 sec
144Gd Eu +  + Energy
T1/2 = 4.5 min

18. Beta decay, e- 60Co 2.405 Mev 1.173 Mev Gamma ray 1.332 Mev
Gamma Ray Emission, the Nuclear Particles in the Nucleus dropping from excited states to their ground states. Example is the decay of cobalt – 60 to excited states in nickel – 60, which then decay to the ground state of 60Ni.
Beta decay, e-
60Co
2.405 Mev
1.173 Mev Gamma ray
1.332 Mev
1.332 Mev Gamma ray
Ground state of 60Ni

19. Natural Decay Series of Existing Isotopes
40K Ar
T1/2 = 1.29 x 109yrs
232 Th Pb
T1/2 = 1.4 x 1010yrs
235U Pb
T1/2 = 7 x 108yrs
238U Pb
T1/2 = 4.5 x 109yrs

20. Figure 21.2: Decay series

22. Natural Decay series for Uranium 238
238U Th
234Pa
234U Th Ra Rn Po Pb
218At Bi Tl
214Po Pb Hg
=  decay Bi Tl
=  decay Po Pb
238U  decays and 6  decays leaves you with Pb

23. Natural Decay series for Uranium 235
235U Th
231Pa Ac Fr At Bi
227 Th Ra Ra Po Pb
215At Bi Tl
211Po Pb
=  decay
=  decay
235U  decays and 4  decays leaves you with Pb

24. Natural Decay series for Thorium 232
232 Th Ra
228Ac
228 Th Ra Rn Po Pb
212Bi Tl
212Po Pb
=  decay
=  decay
232 Th  decays and 4  decays leaves you with Pb

26. Figure 21.3: The decay of a 10.0 -g sample of strontium-90 over time.

27. Figure 21.4: change in the amount of Molybdenum - 99 with time

28. Figure 21.5: Schematic diagram of a cyclotron

29. Physicist works with a small cyclotron at the University of California at Berkeley.
Source: Corbis

30. CERN, the world's largest particle accelerator, lies at the foot of the Jura Mountains near Geneva, Switzerland.

31. Figure 21.6: Diagram of a linear accelerator

32. Accelerator tunnel at Fermilab, a high-energy particle accelerator in Batavia, Illinois.
Source: Fermilab Batavia, IL

34. Carbon-14 radioactivity is often used to date human skeletons found at archaeological sites
Source: University of Pennsylvania Photo Archives

36. Figure 21.8: Consumption of Na131I
Normal Thyroid An Enlarged Thyroid
Source: Visuals Unlimited

37. Figure 21.9: Binding energy per nucleon as a function of mass number.

38. Units used for Nuclear Energy Calculations
electron volt - (ev)
The energy an electron acquires when it moves through
a potential difference of one volt:
1 ev = x 10-19J
Binding energies are commonly expressed in units
of megaelectron volts (Mev)
1 Mev = 106 ev = x J
A particularly useful factor converts a given mass defect
in atomic mass units to its energy equivalent in electron
volts:
1 amu = x 106 ev = Mev

39. Binding Energy per Nucleon of Deuterium
Deuterium has a mass of amu.
Hydrogen atom = 1 x amu = amu
Neutrons = 1 x amu = amu
amu
Mass difference = Theoretical mass - actual mass
= amu amu = amu
Calculating the binding energy per nucleon:
Binding Energy amu x Mev / amu
Nucleon nucleons
= Mev / nucleon =

40. Calculation of the Binding Energy per Nucleon for Iron- 56
The mass of Iron -56 is amu, it contains 26 protons and
30 Neutrons
Theoretical Mass of Fe - 56 :
Hydrogen atom mass = 26 x amu = amu
Neutron mass = 30 x amu = amu
amu
Mass defect =Actual mass - Theoretical mass:
amu amu = amu
Calculating the binding energy per nucleon:
Binding Energy amu x Mev / amu
nucleon nucleons =
= Mev / nucleon

41. Calculation of the Binding Energy per Nucleon for Uranium - 238
The actual mass of Uranium = amu, and it has
92 protons and 146 neutrons
Theoretical mass of Uranium 238:
Hydrogen atom mass = 92 x amu = amu
neutron mass = 146 x amu = amu
amu
Mass defect = Actual mass - Theoretical mass:
amu amu = amu
Calculating the Binding Energy per nucleon:
Binding Energy amu x Mev / amu
mucleon nucleons =
= Mev / nucleon

42. Mass and Energy in Nuclear Decay - I
Consider the alpha decay of 212Po T1/2 = 0.3 s
212Po Pb  + Energy
g/mol g/mol g/mol
Products = = g/mol
Mass = Po - Pb +  =
g/mol
E = mC2 = (1.070 x 10-5 kg/mol)(3.00 x 108m/s)2
= 9.63 x 1011 J/mol
9.63 x 1011 J/mol
6.022 x 1023 atoms/mol
= ____________________ J/atom

43. Mass and Energy in Nuclear Decay - II
The Energy for the Decay of 212Po is 1.60 x 10-12J/atom
1.60 x 10-12J/atom
1.602 x J/ev
= 1.00 x 107 ev/atom
10.0 x 106 ev x 10-6 Mev
atom ev x
= Mev/atom !!!!!
The decay energy of the alpha particle from 212Po is = 8.8 Mev !!!!

44. Figure 21.10: Both fission and fusion produce more stable nuclides and are thus exothermic.

45. Figure 21.11: Upon capturing a neutron, the 235U nucleus undergoes fission to produce two lighter nuclides, free neutrons (typically three), and a large amount of energy.

46. Figure 21.12: Representation of a fission process in which each event produces two neutrons, which can go on to split other nuclei, leading to a self-sustaining chain reaction.

47. Figure 21.13: If the mass of the fissionable material is too small, most of the neutrons escape before causing another fission event; thus the process dies out.

49. Figure 21.14: Nuclear power plant

50. Breeder reactor at a nuclear power plant in St
Breeder reactor at a nuclear power plant in St. Laurent-Des Eaux, France.
Source: Stock Boston

51. A Uranium "button" for use as a fuel in a nuclear reactor.

52. Figure 21.15: Schematic of a reactor core

53. Neutron Induced Fission - Bombs and Reactors
There are three Isotopes with sufficiently long half-lives and a
significant fission cross-sections that are known to undergo
neutron induced fission, and are useful in fission reactors, and
Nuclear weapons. Of these only one exists on earth ( 235U which
exists at an abundance of 0.72% of natural Uranium)and that is the
isotope that we use in nuclear reactors for fuel and some weapons.
The three isotopes are:
233U T1/2 = 1.59 x 105 years sigma fission = 531 barns
235U T1/2 = 7.04 x 108 years sigma fission = 585 barns
239Pu T1/2 = 2.44 x 105 years sigma fission = 750 barns

54. Breeding Nuclear Fuel
There are two relatively common heavy Isotopes that will not undergo
neutron induced fission, that can be used to make other Isotopes that
do undergo neutron induced fission, and can be used as nuclear fuel in
a nuclear reactor.
Natural Thorium is 232 Th which is common in rocks.
232 Th + 10n Th + Energy T1/2 = 22.3 min
233 Th Pa +  + Energy T1/2 = 27.0 days
233Pa U +  + Energy T1/2 = 1.59 x 105 yrs
Natural Uranium is 238U which is common in rocks as well.
238U n U + Energy T1/2 = 23.5 min
239U Np +  + Energy T1/2 = 2.36 days
239Np Pu +  + Energy T1/2 = years

55. A schematic diagram of the tentative plan for deep underground isolation of nuclear waste.

56. Disposal system
Source: AP/Wide World Photos

57. Figure 21.16: Plot of energy versus the separation distance

59. Hydrogen Burning in Stars and Nuclear Weapons
1H + 1H H +  Mev
1H + 2H He Mev
2H + 2H He + 1n Mev
2H + 2H H H mev
2H + 3H He + 1n Mev Easiest!
Highest
2H + 3He He + 1H Mev cross
section!
1H + 7Li He + 4He Mev

60. Helium Burning Reactions in Stars
12C + 4He O
16O + 4He Ne
20Ne + 4He Mg
24Mg + 4He Si
28Si + 4He S
32S + 4He Ar
36Ar +4He Ca

61. Image of a portion of the Cyngus Loop supernova remnant taken by the Hubble space telescope.
Source: NASA

62. Positron Emission Tomography (PET) – A new and
Important Tool in Imaging Research
In the technique of positron Tomography, a positron emitting isotope
Is included into a molecule that is incorporated into a chemical reaction.
The positron emitted during the decay of the isotope will analite with an
Electron and emit two 511 kev gamma rays that can then be detected,
and the location of the decaying isotope isolated accurately.
B+ + e Energy Two Gamma rays at 180o
511 kev
511 kev
The two gamma
rays come away
at 180o.
e- + B+
Common Positron emitting Isotopes: 15O, T1/2 = 122s ; 18F, T1/2 = 1.83 hr
11C, T1/2= 20.3 min , 13N, T1/2 = 9.97 min , ETC

63. Positron Emission Tomograph
The Tomograph is an
instrument that is a ring
of gamma ray detectors
that react very fast to
gamma rays, and by
measuring the time each
detector receives the signal
one can locate the point of
origin of the gamma ray to a precision of + 1 cm in a
human being or any other physical object, with out
any in vivo investigation. The detectors must have a
capability of measuring up to ps per pulse. _ _

64. Units of Radiation dose
rad = radiation - absorbed dose
the quantity of energy absorbed per kilogram of
tissue 1 rad = 1 x 10-2 J / kg
rem = roentgen equivalent for man, the unit of radiation
dose for a human:
1 rem = 1 rad x RBE
RBE = 10 for 
RBE = 1 for x-rays,  -rays, and ’s

67. Examples of Typical Radiation Doses
from Natural and Artificial Sources - I
Source of Radiation Average adult Exposure
Natural
Cosmic radiation mrem/yr
Radiation from the ground
From clay soil and rocks ~ mrem/yr
In wooden houses mrem/yr
In brick houses mrem/yr
In light concrete houses mrem/yr
Radiation from the air (mainly radon)
Outdoors, average value mrem/yr
In wooden houses mrem/yr
In brick houses mrem/yr
In light concrete houses mrem/yr
Internal radiation from minerals in
tap water and daily intake of food ~ 40 mrem/yr
( 40K, 14C, Ra)

68. Examples of Typical Radiation Doses from
Natural and Artificial Sources - II
Source of Radiation Average Adult Exposure
Artificial
Diagnostic x-ray methods
Lung (local) rad/film
Kidney (Local) rad/film
Dental (dose to the skin) < 1 rad/film
Therapeutic radiation treatment locally < 10,000 rad
Other sources
Jet flight (4 hrs) ~ 1 mrem
Nuclear tests < 4 mrem/yr
Nuclear power industry < 1 mrem/yr
Total Average Value mrem/yr

69. Examples of Typical Radiation Doses from
Natural and Artificial Sources - III
From Kotz & Percell, Freshman Chemistry text
Smoke detectors millirem/year
Smoking Tobacco(1.5 packs a day) “
10 Airline flights “
Airline Crew “
Hazards equivalent to the radiation dose of 10 mrem/year
3250 km travel by car
600 km travel by velocipede
150 km motorcycle
25 liters of wine
100 cigarettes smoked
1 diagonistic x-ray

70. Acute Effects of a Single Dose of Whole-Body Irradiation - I
Dose Lethal Dose
(rem) Effect Population (%) No. of Days
Possible late effect; possible
chromosomal aberrations
Temporary reduction in
white blood cells
Temporary sterility in men
(100+ rem = 1 yr duration)
“Mild radiation sickness”:
vomiting, diarrhea, tiredness
in a few hours
Reduction in infection resistance
Possible bone growth retardation
in children

71. Acute Effects of a Single Dose of Whole-Body Irradiation - II
Dose Lethal Dose
(rem) Effect Population (%) No. of Days
Permanent sterility in Women
“Serious radiation sickness”:
marrow/intestine destruction
Acute illness, early deaths
Acute illness, death in hours
to days