1. The ABG's (or Alpha, Beta, Gamma) of Radioactivity

2. Ch. 6 Notes Day 1

3. Science Park HS -- Honors Chemistry
Objectives
SWBAT state what radioactivity is, where these rays come from, what each ray is made of and state why they are dangerous.
SWBAT identify 4 pioneer scientists who made important contributions to understanding radioactivity
SWABT to explain the meaning of “half-life”.
Student will be asked to find any sources of Radioactivity in his/her environment
Science Park HS -- Honors Chemistry

4. Early Pioneers in Radioactivity
Rutherford:
Discoverer Alpha and Beta rays 1897
Roentgen:
Discoverer of X-rays 1895
The Curies:
Discoverers of Radium and Polonium
Becquerel:
Discoverer of Radioactivity 1896

5. What do we mean by Radioactivity?
Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves.
There are numerous types of radioactive decay. The general idea:
An unstable nucleus releases energy to become more stable

6. Kinds of Radioactivity
The three main decays are Alpha, Beta and Gamma

7. Radiation Radiation comes from the nucleus of an atom.
Unstable nucleus emits a particle or energy  alpha
 beta
 gamma

8. U He Th Alpha Particle  He **Same as a Helium Nucleus 234 92 4 2 230
Symbol
Particle
Charge
Mass (amu)  4 He 2+ 2
234 U 92 4 He 2
230 Th 90
**Same as a Helium Nucleus

9. Pt e Ir Beta Particle  e **Super charged electron 192 77 -1 192 78 1-
Symbol
Particle
Charge
Mass (amu)  e 1- -1
192 Ir 77 e -1
192 Pt 78
**Super charged electron

10. Gamma Particle
Symbol
Particle
Charge
Mass (amu) 
190 Os 76 
190 Os 76
**Pure radiation energy! Doesn’t change the radioisotope, just makes it more stable

11. Radiation Protection
Shielding
alpha – paper, clothing
beta – lab coat, gloves, aluminum foil
gamma- 6 inches of lead, 12 feet of concrete
Limit time exposed
Keep distance from source

12. Radiation Protection

13. Learning Check
Write the nuclear equation for the beta emitter Co-60.

14. Solution 60Co 60Ni + 0 e 27 28 -1 Write the nuclear equation for the
Beta emitter Co-60.
60Co Ni e

15. Producing Radioactive Isotopes
Bombardment of atoms produces radioisotopes
= = 60
59Co n Mn H e
= = 27
cobalt neutron manganese alpha
atom radioisotope particle

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

17. Solution
What radioactive isotope is produced in the following bombardment of boron?
10B He N n
nitrogen
radioisotope

18. Sources of Radioactivity
Primordial - from before the creation of the Earth
Cosmogenic - formed as a result of cosmic ray interactions
Human produced - enhanced or formed due to human actions (minor amounts compared to natural)

19. Where are the Sources of Radioactivity?
Naturally Occurring Sources:
Radon from the decay of Uranium and Thorium
Potassium -40 – found in minerals and in plants
Carbon 14 – Found in Plants and Animal tissue
Manmade Sources:
Medical use of Radioactive Isotopes
Certain Consumer products –(eg Smoke detectors)
Fallout from nuclear testing
Emissions from Nuclear Power plants

20. Radioactivity – Is it a Health Problem?
The Alpha, Beta and Gamma particles all add energy to the body’s tissues. The effect is called the Ionizing Energy. It can alter DNA.
Even though Alpha particles are not very penetrative if the decaying atom is already in the body (inhalation, ingestion) they can cause trouble.
The Time, Distance and Shielding principle
Science Park HS -- Honors Chemistry

21. Radiation Exposure to Americans
Science Park HS -- Honors Chemistry

22. Ch. 6 Notes Day 2

23. Objectives
SWBAT identify and explain the purpose of the three main components of a nuclear power plant
SWBAT explain how humans control fission chain reactions to generate power inside the nuclear core
SWBAT explain some of the measures nuclear power plants take to ensure safety

24. Parts of a Nuclear Power Plant

25. Main Parts of a Nuclear Power Plant
- Containment Building seals in nuclear reactor
- Radioactive fuel rods made of Uranium or Plutonium heat water with radiation **makes water radioactive
- Hot radioactive water turns water inside heat exchanger to steam
- Steam from heat exchanger spins turbines
- Turbines spin rod inside generator, to produce electricity
- Steam turned to water in condenser, then returned to heat exchanger
- Cold air in cooling tower or cold river water used to cool down the condenser
- Cooling towers only make steam!!!
The water in each of the three sections, is contained in those section to prevent contamination!!!

26. Reactor and Fission Chain Reaction

27. Nuclear Chain Reaction (Fission)
Nuclear Reactor Core
Moderator
Nuclear Chain Reaction (Fission)
More Stable

28. Nuclear Power Pros & Cons

29. Ch. 6 Notes Day 3

30. Objectives SWBAT define radioactivity
SWBAT explain the concept of half-life through experimentation in the lab

31. Vocabulary
Radioactivity – process where an unstable atomic nucleus emits charged particles and energy to become more stable.
Nuclear Radiation- charged particles emitted from radioactive nuclei called radioisotopes.
Alpha Decay – emits an alpha particle. Alpha particles can be stopped with paper
Beta Decay – emits a beta particle. Beta particles can be stopped with aluminum foil
Gamma Decay – emits gamma rays. Gamma rays are pure energy, and can only be stopped with 12 or more feet of concrete. (This is what made the Hulk…)

32. Half Life
Half-Life – time required for half of a radioisotope to decay.
Used for dating old materials like rocks
Radon-222 half-life of 3.82 days
Uranium-238 half-life of 4.47 billion years
# of Half-lives 1 2 3 4 5 6
Amount of Radio Isotope Left
1/4
1/8
1/16
1/32
1/64
Percentage Left
100%
50%
25%
12.5%
6.25%
3.125%
1.56%

33. Ch. 6 Notes Day 4

34. Objectives
SWBAT use the half-life equation to determine the amount of an radioisotope that remains after a certain amount of time
SWBAT to determine how many half-lives have elapsed, given the starting and ending amounts of a substance.

35. Half-Life of a Radioisotope
The time for the radiation level to fall (decay) to one-half its initial value
decay curve
8 mg 4 mg 2 mg mg
initial 1
half-life 2 3

36. Examples of Half-Life Isotope Half life C-15 2.4 sec Ra-224 3.6 days
I days
C years
U years

37. Half-Life Equation # of half-lives (n) =
N(t) - Amount of radioisotope remaining
No – Amount of radioisotope to start (at time = 0)
t - time elapsed
t1/2 – half- life

38. Learning Check
The half life of I-123 is 13 hr. How much of a 64 mg sample of I-123 is left after 26 hours?

39. Solution t1/2 = 13 hrs 26 hours = 2 x t1/2 Amount initial = 64mg
Amount remaining = 64 mg x ½ x ½
= 16 mg