1. Radioactivity
Nucleus – center of the atom containing protons and neutrons
How are the protons and neutrons held together?
Strong Force - an attractive force that holds protons and neutrons together
The protons and neutrons must be close together for this force to keep them together
As the nucleus increases in size, the strong force diminishes and the electrical force (force between charges) becomes more powerful

2. Radioactivity – process of nuclear (nucleus) decay
Stability of Nuclei
Larger nuclei are less stable – all nuclei that contain more than 83 protons are radioactive
The ratio of neutrons to protons also determines if an element is radioactive
Nuclei with too many or too few neutrons compared to protons are usually unstable, and thus, radioactive

3. C C Nucleus numbers representation
A nucleus can be represented by the following isotope notation
In this carbon-12 isotope, there are 6 protons and 6 neutrons, which makes it stable and not radioactive
What would carbon-14 look like?
Would carbon-14 be radioactive? Why?
mass number C 12
element symbol 6
atomic number C 14 6
radioactive, because it has too many neutrons compared to its protons

4. Nuclear Radiation – when an unstable nucleus decays, particles and energy are emitted (given off)
3 types of Nuclear Radiation
Alpha Particles
Beta Particles
Gamma Rays

5. Radioactivity Uses Treating cancer Internal inspection
Radioactive dating of artifacts
Tracing
Smoke detectors
Sterilization
Food irradiation
Thickness monitoring
Nuclear energy

6. He Alpha Particles – made of 2 protons and 2 neutrons
Also known as a helium-4 nucleus with a charge of 2+ (no electrons)
As the alpha particle leaves the atom, it passes through other matter and takes electrons, leaving behind ions
This process causes it to lose much of its energy
An atomic mass unit of 4
can be stopped with a sheet of paper or clothing
Symbol He 4 2

7. Transmutation – process of changing one element to another through nuclear decay
- Alpha particle nuclear reaction
During the transmutation, the total mass and charges of the nuclei at the end are the same as the nucleus at the beginning + Po
210 84 Pb
206 82 He 4 2 +
+84
+82 +2

8. Beta Particles – a neutron decays into a proton and emits an electron in the process
the beta particle has a negative charge
Smallest of the radiation particles – has an atomic mass unit of
Much faster and more penetrating than alpha particles
Can be stopped by a sheet of aluminum foil or wood
Symbol e -1

9. I Xe e Beta particle nuclear reaction - +
During the transmutation, the total mass and charges of the nucleus and the electron emitted at the end are the same as the beginning - + I
131 53 Xe
131 54 e -1 +
+53
+54 -1

10. Gamma Rays – electromagnetic wave
usually emitted from a nucleus when an alpha decay or beta decay occurs
gamma rays have no mass or charge and travel at the speed of light
Deepest penetrating of radiation, but is not as damaging to living tissue as alpha and beta
Requires dense, thick materials such as concrete blocks or lead to stop

11. Alpha particles have a greater
charge and mass than beta
particles and gamma rays do.
Alpha particles travel about
7 cm through air and are
stopped by paper or clothing.
Beta particles have a 1 or 1 charge and almost no mass. They are more penetrating than alpha particles. Beta particles travel about 1 m through air but are stopped by 3 mm of aluminum.
Gamma rays have no charge or mass and are the most penetrating. They are blocked by very dense, thick materials,
such as a few centimeters of lead or a few meters of concrete.

12. Radioactive Half-life – the amount of time it takes for half of the nuclei in a sample of an isotope to decay
Example, the half-life of (hydrogen-3) is years.
The H-3 will beta decay to He-3
If a sample has 20 atoms of hydrogen, after years, 10 atoms will have decayed to He-3, and the other 10 will still be H-3
After 12.3 more years, another 5 will have decayed to He-3, and 5 will still be H-3 H 3 1

14. Radioactive Dating – using known half-lives to date certain rocks, fossils, and other materials
Carbon dating – radioactive isotope carbon- 14 is found in plants and animals.
Has a half-life of 5,730 years
Used to get the approximate age of plants and animals up to 50,000 years
Uranium Dating – used to date some rocks that contain small amounts of uranium

17. Solving Half-Life problems
Make a HMT, chart like shown:
H=Half Lives
M=Mass
T=Time
%= per cent left
Fraction=fraction left
For the mass, divide by two for each half life
For the time, add the half life time.

18. A. Potassium-42 has a half-life of 12. 4 hours
A. Potassium-42 has a half-life of hours. How much of an 848 g sample of potassium-42 will be left after 62.0 hours?
B. If the half-life of iodine-131 is 8.10 days, how long will it take a g sample to decay to 6.25 g?
C. What is the half-life of a g sample of nitrogen-16 that decays to 12.5 g of nitrogen-16 in 21.6 s?

19. Nuclear Reactions
Make sure the atomic numbers are and the mass numbers are equal on either side of the arrow.

20. Nuclear Reactions
Nuclear Fission – The process of splitting a nucleus into several smaller nuclei
Only large nuclei, such as uranium and plutonium, undergo fission
A neutron collides with a large nucleus and splits in two
Some of the mass actually converts to a tremendous amount of energy Kr 90 36 n
+ energy n n U
235 92 Ba
142 56 n

21. Chain Reaction - When a nuclear fission reaction occurs, the neutrons emitted can strike other nuclei in the sample, and cause them to split.
Critical mass - the amount of material needed to sustain a chain reaction.

22. Nuclear Power – Fission
How a Fission Nuclear Power Plant Works
Energy comes from a controlled fission nuclear reaction
Uses Uranium -235
As the nuclei split, tremendous heat is released
Heat is used to produce steam that turns a turbine which rotates an electric generator
n + 1 U
235 92
Sn +
Mo + n
132
101 50 42 3

23. Nuclear Power – Fission
Advantages
does not release pollutants like fossil fuels
provides about a million times more energy per pound than fossil fuels
Disadvantages
radioactive material could be released into environment in an accident
disposal of waste material is expensive and difficult
uranium is non- renewable

24. Nuclear Fusion – two nuclei of smaller mass are combined to form one larger nucleus
Produces even more energy than fission
Temperature must be extremely hot (millions of degrees Celsius) for nuclei to be moving so fast that they get close enough for fusion to occur
H-1
+ energy
He-3
H-2

25. Nuclear Power – Fusion How Fusion Nuclear Power Works
Fusion of 2 small nuclei
Hydrogen nuclei fuse to form Helium
Must occur at extremely high temperatures
Releases huge amounts of energy, even more than fission reactions
H + 1 e -1 He 4 2

26. Nuclear Power – Fusion Advantages Disadvantages
uses hydrogen as a fuel which is very abundant on earth
the product is helium, a non-radioactive and non-polluting element
most concentrated energy source known
Disadvantages
occurs only at high temps of millions of degrees Celsius
use more energy to produce the reaction than energy given off
containment of the reaction will be extremely difficult