1. 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

2. The Nucleus
Remember that the nucleus is comprised of the two nucleons, protons and neutrons.
The number of protons is the atomic number.
The number of protons and neutrons together is effectively the mass of the atom.

3. Isotopes
Not all atoms of the same element have the same mass due to different numbers of neutrons in those atoms.
There are three naturally occurring isotopes of uranium:
Uranium-234
Uranium-235*
Uranium-238

4. Nuclide Symbols

5. Nuclide Symbols

7. Isotopes
Two Categories
Unstable – isotopes that continuously and spontaneously break down/decay in other lower atomic weight isotopes
Stable – isotopes that do not naturally decay but can exist in natural materials in differing proportions

8. Radioactivity
It is not uncommon for some isotopes of an element to be unstable, or radioactive.
We refer to these as radioisotopes.
There are several ways radioisotopes can decay and give off energy known as radiation.

11. Types of Radioactive Decay Alpha Decay
Loss of an -particle (a helium nucleus) He 4 2 U
238 92
 Th
234 90 He 4 2 +

12. Types of Radioactive Decay Beta Decay
Loss of a -particle (a high energy electron)  −1 e or I
131 53 Xe 54
 + e −1

13. Types of Radioactive Decay Gamma Emission
Loss of a -ray (high-energy radiation that almost always accompanies the loss of a nuclear particle) 

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

15. Penetrating Ability

21. Geologic Time Radioactive Isotopes used in Geologic Dating
Parent Daughter half-life (y)
U-238 Lead billion
U-235 Lead million
Thorium 232 Lead Billion
K-40 Argon billion
R-87 Sr billion
C-14 N
Half-life = time it takes for 1/2 of the parent mass to decay into the daughter mass

23. Geologic Time 14Carbon Dating
Dating is accomplished by determining the ratio of 14C to non-radioactive 12C which is constant in living organisms but changes after the organism dies
When the organism dies it stops taking in 14C which disappears as it decays to 14N

27. Forensic 14Carbon Cases Dead Sea Scrolls – 5-150 AD
Stonehenge – 3100 BC
Hezekiah’s Tunnel BC

28. Forensic 14Carbon Cases ● Cave painting at Lascaux, France
● King Arthur’s Table in Winchester Castle, England 14C dated to 13th century AD
● Cave painting at Lascaux, France
14C dated to 14,000 BC
● Rhind Papyrus on Egyptian math 14C dated to 1850 BC

29. Forensic 14Carbon Cases 14C dated 1260-1390 AD
● The Shroud of Turin was
14C dated AD
which suggests that it is a fake
● However, recent evaluation
shows that the sample measured
was from a medieval patch and/or
that it was seriously contaminated
with molds, waxes, etc
●New estimates date the shroud from
ybp bases on vanillin
retention

30. Forensic 14Carbon Cases
Nuclear testing during put large amounts of 14C into the atmosphere which was incorporated into the enamel of human teeth. Because such testing stopped the 14C input ended and the 14C in the teeth decayed at a fixed rate allowing dating of the teeth

31. Nuclear Reactions
Alpha emission
Note that mass number goes down by 4 and atomic number goes down by 2.
Nucleons (nuclear particles… protons and neutrons) are rearranged but conserved

32. Nuclear Reactions Beta emission
Note that mass number is unchanged and atomic number goes up by 1.

33. Write Nuclear Equations!
Write the nuclear equation for the alpha decay of radon-222
222Rn  218Po He
Write the nuclear equation for the beta emitter Co-60.
60Co  60Ni e 86 84 2 -1 27 28

34. Bellringer Fill in Chart
Radioactive Particle
Nuclear Symbol
Pertinent Information
alpha
beta
gamma
positron 4 He 2
helium atom without any electrons e -1
high energy electron, no mass with a negative charge γ
high energy ray with no mass and no atomic number e +1
mass of an electron but a positive charge

35. Neutron-Proton Ratios
Any element with more than one proton (i.e., anything but hydrogen) will have repulsions between the protons in the nucleus.
A strong nuclear force helps keep the nucleus from flying apart.
Neutrons play a key role stabilizing the nucleus.
Therefore, the ratio of neutrons to protons is an important factor.

36. Stable Nuclei
The shaded region in the figure shows what nuclides would be stable, the so-called belt of stability.

37. Neutron-Proton Ratios
For smaller nuclei (Z  20) stable nuclei have a neutron- to-proton ratio close to 1:1

38. Neutron-Proton Ratios
As nuclei get larger, it takes a greater number of neutrons to stabilize the nucleus.

39. Stable Nuclei Nuclei above this belt have too many neutrons.
They tend to decay by emitting beta particles.

40. Stable Nuclei Positron = 0e
Nuclei below the belt have too many protons.
They tend to become more stable by positron emission or electron capture.
Positron = 0e +1

41. Stable Nuclei
There are no stable nuclei with an atomic number greater than 83.
These nuclei tend to decay by alpha emission.

42. Radioactive Series
Large radioactive nuclei cannot stabilize by undergoing only one nuclear transformation.
They undergo a series of decays until they form a stable nuclide (often a nuclide of lead).

43. Nuclear Transformations
Nuclear transformations can be induced by accelerating a particle and colliding it with the nuclide.
These particle accelerators are enormous, having circular tracks with radii that are miles long.

44. Measuring Radioactivity
One can use a device like this Geiger counter to measure the amount of activity present in a radioactive sample.
The ionizing radiation creates ions, which conduct a current that is detected by the instrument.

45. Energy in Nuclear Reactions
There is a tremendous amount of energy stored in nuclei.
Einstein’s famous equation, E = mc2, relates directly to the calculation of this energy.
In chemical reactions the amount of mass converted to energy is minimal.
However, these energies are many thousands of times greater in nuclear reactions.

46. Nuclear Fission How does one tap all that energy?
Nuclear fission is the type of reaction carried out in nuclear reactors.

47. Nuclear Fission
Bombardment of the radioactive nuclide with a neutron starts the process.
Neutrons released in the transmutation strike other nuclei, causing their decay and the production of more neutrons.
This process continues in what we call a nuclear chain reaction.

48. Trafficking Nuclear Materials
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

49. Man-made Radioactive Isotopes
In 1997, two pieces of stainless steel contaminated with alpha-emitters were found in a scrap metal yard in Germany.
Source was identified as a fast-breeder reactor in Obninsk, Russia
Smuggled Plutonium – can identify the reactor type in which the fuel was originally radiated and the type of plant where the material was subsequently reprocessed
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

50. Weapons-grade Plutonium
The isotopic composition of plutonium can indicate INTENT
In 1994, a small lead cylinder discovered in a garage in Tengen on the Swiss-German border was found to contain plutonium metal, isotopically enriched to 99.7%
Weapons-grade Pu-239
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

51. Radioactive Fingerprints
The first ever radioactive fingerprint has recently been identified on an object contaminated with alpha- emitting isotopes
Preserving the conventional chain of evidence whilst dealing with radioactive samples can be problematic
For example – lifting fingerprints and swiping for radioactive contamination cannot both be carried out
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License

52. If there are not enough radioactive nuclides in the path of the ejected neutrons, the chain reaction will die out.
Therefore, there must be a certain minimum amount of fissionable material present for the chain reaction to be sustained: Critical Mass.

53. Nuclear Reactors
In nuclear reactors the heat generated by the reaction is used to produce steam that turns a turbine connected to a generator.

54. Nuclear Reactors
The reaction is kept in check by the use of control rods.
These block the paths of some neutrons, keeping the system from reaching a dangerous supercritical mass.

55. Nuclear Fusion
nuclear fusion is a nuclear reaction in which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus.
During this process, matter is not conserved because some of the mass of the fusing nuclei is converted to energy which is released.
Fusion is the process that powers active stars.
Fusion would be a superior method of generating power.
The good news is that the
products of the reaction are
not radioactive.
The bad news is that in order to achieve fusion, the material must be in the plasma state at several million kelvins.

56. Weapons whose explosive output is exclusively from fission reactions are commonly referred to as atomic bombs or atom bombs
misnomer because the energy actually comes from nucleus
Many fission products are either highly radioactive (but short- lived) or moderately radioactive (but long-lived), and as such are a serious form of radioactive contamination if not fully contained. Fission products are the principal radioactive component of nuclear fallout.

57. Thermonuclear bombs work by using the energy of a fission bomb to compress and heat fusion fuel.
When the fission bomb is detonated, gamma rays and X- rays emitted first compress the fusion fuel, then heat it to thermonuclear temperatures
Tsar Bomb