1. The Nucleus

2. Nuclear Concepts to Master
Compare the benefits and dangers of radioactivity.
Which isotopes are used for treatments of which illnesses?
How is background radioactivity different from natural radioactivity?
How did the transuranium elements come into existence?
Does fusion or fission produce more energy?
What are the equations for fission and fusion?
Which reaction has not been achieved and which one is used in nuclear power plants (fission or fusion)?
Compare fission and fusion.
What is the shielding effect?
Write and balance equations that involve alpha, beta, neutron, positron, or proton particles and gamma radiation.
Which direction will alpha particles move when placed in an electric field?
What is the band of stability?
What is the difference between and artificial and natural transmutation?
Use table N and O to solve problems.
Solve problems involving half-life using the equation or the “walk-the-dog” method.
Half-life is constant!
What is a Geiger counter used for?
How do scientist use uranium isotopes to date rocks?
How do scientist use carbon isotopes to date mummies?
Why do doctors use radioisotopes with shorter half-lies when performing a medical procedure?
Which radioisotope is used for sterilizing things like medical equipment?
Which isotope is used in the irradiation of meat?

3. Vocab Labs Absorption Alpha particle Artificial radioactivity
Background radioactivity
Beta particle
CPM
Daughter nucleus
Decay
Emission
Endothermic
Exothermic
Fission
Frequency
Fusion
Gamma radiation
Half-life
Ionization
Irradiated
Isotope
Natural radioactivity
Nuclides
Penetrating distance
Positron
Radioactive isotopes
Radioactivity
Radionuclide
Shielding
Transmutation
Transuranium elements
Wavelength
Labs
Radioactive decay of Uranium
Half-Life Simulation

4. Electromagnetic Spectrum
Ionizing and non-ionizing radiation – ionizing refers to the ability of the atom to become an ion, electrons jump away from (cation) or to an atom (anion).
Frequency correlated with energy and ionizing ability
We’ve been focusing on electrons, how many each element has and where they are. Show website.
Now it’s time to focus on the nucleus
LESS harmful to the body
MORE harmful to the body
Ionization is the ability of an atom to become an ion (charged particle).
If electrons are lost a cation is formed.
If electrons are gained an anion is formed.
Ionization is the ability of an electron to jump away from or to another atom.

5. Ionizing Power
The ionizing power of ionizing radiation measures how many ions are formed in a given area when the radiation passes through it.
It indicates how densely packed incidents of ionization will be. In human tissue ionization occurring in a limited location means concentrated tissue damage and will increase the probability of cell death or mutations due to DNA damage.

6. Radioactivity 31H = H31 =H3= H-3 Unstable isotopes
To become more stable, the atom spits out subatomic particles and rays of energy
This release of subatomic particles and rays is radioactivity
Review isotopes
31H = H31 =H3= H-3

7. In the band of stability, atoms are stable
In the band of stability, atoms are stable. The ratio n/p  is 1 for low nuclear masses and it increases steadily up to 1.5 for high nuclear masses.
Unstable Nucleus?
In region A, a nucleus with too many neutrons is unstable because not enough of them are paired with protons.
In region B, a nucleus with too many protons has too much repulsive electrical interactions to be stable.

8. Sulfur 94.93 0.78 4.29 Isotope Atomic # Mass # of Protons
# of Neutrons
# of Electrons
% found in NATURE
S-32
94.93
S-33
0.78
S-34
4.29
Calculate ATOMIC MASS

9. Map of U.S. Natural Radioactivity
The colors indicate uranium concentrations: red is high, yellow is medium, blue is low.

10. Natural Radioactivity
The earth is radioactive (air, water, and soil).
Due to elements that spontaneously and uncontrollably emit radioactivity.
Radioactive elements are also called:
Radioactive isotopes
Radionuclide
Nuclides

11. Types of Radiation - Beta
A beta particle is like a fast electron.
It’s mass is small like an electron’s.
Since it’s small, it can penetrate your skin!
Beta Decay

12. Types of Radiation - Positron
A positron  is an like an electron but with a positive charge!
It’s small like an electron
It has a charge of +1 (opposite to an electron!)
When it meets with an electron it annihilates it!
Often when nuclei that release positrons also release gamma radiation.
Can penetrate your skin!
Positron Decay

13. Types of Radiation - Alpha
An alpha particle  is a particle that is made up of two protons and two neutrons.
It is therefore a helium nucleus with a mass number of 4 and a atomic number of 2. 42He
It has a mass of 4.0 amu - massive on a nuclear scale!
Too BIG to penetrate your skin.

14. Types of Radiation - Gamma
The gamma ray  is a photon of high energy.
It has no mass.
It has no charge.
Can penetrate your skin!
For gamma ray emission to occur the nucleus must still be in an unstable state after emitting an alpha, beta or positron particle. So to become more stable, it spits out more energy.
Gamma radiation released with beta decay

15. Radiation in an Electric Field? ? ?

16. Try # 5 – 9 on your own before clicking to get the answers.

17. These are often referred to a SHIELDS and they
Protect you from radiation. Distance is also a shield.

18. Artificial Radioactivity
Man-made
Stable isotopes are bombarded with particles such as neutrons to cause a nuclear reaction.
Elements with atomic numbers over 92 have been artificially made. They are called the transuranium elements.
(92 is the atomic number of the heaviest naturally occurring element, Uranium.)
Atom Smashers
Nuclear reactors

19. Fission Larger nucleus is split into smaller nuclei
Fission Larger nucleus is split into smaller nuclei. Mass is converted to energy!
Control rods needed in nuclear power plants! WHY? It’s a CHAIN REACTION

20. Fusion Fusion is when two small nuclei combine to form a single bigger nucleus. Mass is converted to energy!

21. Compare Fission Fusion
Produces hazardous waste since nuclear fuel rods last about 3 years.
The used rods are stored underground
As of 2000, the amount stored is metric tons
Fusion
Little to no hazardous waste (He released and no reactor core)
Inexhaustible energy – 1 gallon of sea water contains enough deuterium to support a family of 4 for 1 year.
Why? It’s a CHAIN REACTION

22. Radiation
Effect of distance
Effect of shield
thickness
type

23. Shielding
Shielding protects you from radiation exposure.

24. Determining the type of rxn
Absorption (Always Artificial)
Emission (natural DECAY)
Artificial transmutation
Natural Transmutation (DECAY)
Fission
Fusion

25. Half – Life of Radioisotopes
The time taken for a given sample of a radioisotope to decay so that its radioactivity is one half the initial amount is called the half-life, t½, of that isotope.
The half-life is a constant for the isotope, and shows enormous variations from one isotope to another.
For example, 17F (fluorine-17) has a half-life of 70 seconds, while 238U has a half-life of 4.51 x 109 years. 14C (carbon-14) has a half-life of 5668 years.
The long-lived nature of some waste products of nuclear reactors pose grave ecological problems, as some of these radioisotopes remain dangerously active for tens of thousands of years.
Whereas the short-lived nature of some radioisotopes allow their use in medicine.

26. Rate of Decay – Half Life
Number of Half-lives
Time
years
% Strontium-90 remaining
% Strontium-90 that has decayed
100 1 28 50 2 56 25 75 3 84
12.5
87.5 4
112
6.25
93.75 5
140
3.125
96.875 6
168
1.5625

27. Rate of Decay – Half Life
What’s the half-life of Sr-90?
What type of curve is the above?
What would the graph look like if the
The y-axis was % being transformed?

28. Calculating Half Life
How much 42K will be left in a 320 g sample after 62 h?
Step 1: Look up the half life in Table N, the table of Selected Radioisotopes
12.4 h
Step 2: Set up a table showing the mass, time elapsed, the fraction remaining, and number of half lives.
Step 3: Fill in the table with the starting condition(s) and ending when the full time has elapsed. Time will always start with 0. Fraction will always start as 1, and Half-lives will always start at 0.
Step 4: For each half life elapsed:
a) cut the mass in half
b) increase the time by an amount equal to the half life
c) cut the fraction in half
d) add one to the number of half lives
Mass
Time
Fraction
Half Lives
320 g
0 h 1
320/2 = 160 g
12.4 h
1/2
160/2 = 80 g
= 24.8 h
1/4 2
80/2 = 40 g =
37.2 h
1/8 3
40/2 = 20 g
=49.6 h
1/16 4
20/2 = 10 g
=62 h
1/32 5

29. Calculating Half Life

30. Determining Half – Life from a graph
The table below shows how the activity (in counts per second) of a sample of radioactive material varies in time. Plot a graph of activity against time to determine the half-life of the material.

31. Radioactivity Extremely Dangerous Extremely Beneficial
Nuclear power plants released radioactive substances into the atmosphere during nuclear accidents.
Three Mile Island
Chernobyl
Nuclear Bomb
Extremely Beneficial
Nuclear power plants
Nuclear medicine
Cardiovascular imaging
Bone scanning
Detecting cancers

32. Radiological dating
We can use the natural radioactivity in some objects to date them.
The following slide shows a rock containing naturally occurring radioactive uranium.
As time goes by, the uranium decays to stable lead.
By comparing the proportions of uranium and lead we can determine the approximate age of the rock.

34. Isotopes in Medicine
Nuclear medicine imaging techniques give doctors another way to look inside the human body. The techniques combine the use of computers, detectors, and radioactive substances.
It is very important to consider the half-life of a substance that is to be used for medical purposes.

35. Isotopes in Medicine Co-60 I-131 Beta and gamma emitter
Sterilization of medical equipment
Treatment of malignant tumors
I-131
Iodine-131 is one of the radioactive isotopes of iodine that can be used to test how well the thyroid gland is functioning.

36. Co-60 and Meat
food is irradiated in an area that is surrounded by concrete walls at least 6-feet thick which keep any rays from escaping.
The radiation source, usually Cobalt 60, is held in a resting position in a pool of water.
A conveyor system transports the meat or poultry product to the area.
The radiation source is then raised out of the water and the food is exposed for a defined period of time.
When the source is raised, lights and alarms are sounded to make people aware that the product is being irradiated.
Once the food is irradiated, the source automatically returns to the resting position and the food leaves the area for further processing.

37. Detecting Radioactivity
Geiger Counter
Measures radiation as CPM
Counts per minute
the amount of radioactive material (counts) that is released in one minute
Film Badge
Radioactivity will expose film.
The amount of film exposed indicates the level of exposure to radioactivity.

38.
Control rods stop the chain reaction in nuclear power plants. They contain B which can soak up the neutrons not allowing them to hit the next U atom. They go up and down in the fuel cell which contains the U-235 and neutrons.
Fission/Fusion song – 4 min
Decay song – 3 min
Three mile island info
Yucca mtn, Jan 2008 – Katie Couric
Nuclear waste

39.
Island of Stability
Discovery of element 114
Video – 13 min
Elemental quiz – write answers to hand in.