1. Nuclear Radiation

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

3. Same as a helium nucleus
Alpha Particle
Same as a helium nucleus 4
2 He or 
Two protons
Two neutrons
Mass number
Atomic number

4. Beta Particle  e or  1 An electron emitted from the nucleus
e or  1
A neutron in the nucleus breaks down
n p + e

5. Positron Particle The antiparticle counterpart to the electron
Has an electric charge of +1 0e +1 0b or
positron

6. Gamma Radiation  Pure radiation
Like an X-ray but comes from the nucleus

7. Radiation Protection Shielding alpha – paper, clothing
beta – lab coat, gloves
gamma- lead, thick concrete

8. Radiation Protection

9. Balancing Nuclear Equations
In the reactants and products Atomic numbers must balance and Mass numbers must balance

10. Alpha decay

11. Beta decay
234Th ® 234Pa e 1
beta particle

12. No change in atomic or mass number
Gamma radiation
No change in atomic or mass number
11B 11B 
boron atom in a
high-energy state

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

14. Solution
Write the nuclear equation for the Beta decay of 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 particle

16. Learning Check
What radioactive isotope is produced in the following bombardment of boron? 10B + 4He ? + 1n 5 2 0

17. Solution
What radioactive isotope is produced in the following bombardment of boron? 10B + 4He 13N + 1n

18. Radioactive Isotopes and Half Life

19. Radioactive Isotopes
Radioactive elements are unstable. They decay, and change into different elements over time.
The radioactive isotopes listed below are the most useful for geologic dating of fossils are:
U-238 Half-life = 4.5 Billion Years
K-40 Half-life = 1.25 Billion Years
C-14 Half-life = 5, 730 Years

20. Radioactive Decay and Half Life
Here are some facts to remember:
The half-life of an element is the time it takes for half of the material you started with to decay.
2. Each element has it’s own half-life

21. Radioactive Decay and Half Life
Each element decays into a new element
C14 decays into N14
4. The half-life of each element is constant. It’s like a clock keeping perfect time.
Now let’s see how we can use half-life to determine the age of a rock, fossil or other artifact.

22. Half-life
It can be difficult to determine the ages of objects by sight alone.
Radioactivity provides a method to determine age by measuring relative amounts of remaining radioactive material to stable products formed.
See pages

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

24. Common Isotope Pairs
There are many radioisotopes that can be used for dating.
Parent isotope = the original, radioactive material
Daughter isotope = the stable product of the radioactive decay
See page 307

25. The blue grid below represents a quantity of C14. Each time you click,
one half-life goes by and turns red.
C14 – blue N14 - red
Half
lives
% C14
%N14
Ratio of
C14 to N14
100% 0%
no ratio
As we begin notice that no time has gone by and that 100% of the material is C14

26. The grid below represents a quantity of C14. Each time you click,
one half-life goes by and you see red.
C14 – blue N14 - red
Half
lives
% C14
%N14
Ratio of
C14 to N14
100% 0%
no ratio 1
50%
1:1
After 1 half-life (5730 years), 50% of
the C14 has decayed into N14. The ratio
of C14 to N14 is 1:1. There are equal
amounts of the 2 elements.

27. The blue grid below represents a quantity of C14. Each time you click,
one half-life goes by and you see red .
C14 – blue N14 - red
Half
lives
% C14
%N14
Ratio of
C14 to N14
100% 0%
no ratio 1
50%
1:1 2
25%
75%
1:3
Now 2 half-lives have gone by for a total
of 11,460 years. Half of the C14 that was
present at the end of half-life #1 has now
decayed to N14. Notice the C:N ratio. It
will be useful later.

28. The blue grid below represents a quantity of C14. Each time you click,
one half-life goes by and you see red.
C14 – blue N14 - red
Half
lives
% C14
%N14
Ratio of
C14 to N14
100% 0%
no ratio 1
50%
1:1 2
25%
75%
1:3 3
12.5%
87.5%
1:7
After 3 half-lives (17,190 years) only
12.5% of the original C14 remains. For
each half-life period half of the material
present decays. And again, notice the
ratio, 1:7

30. What is the half life represented in this graph?

31. Practice Problem #1
1) The half life of a radioactive isotope is 3 years. What fraction of the isotope remains after 18 years?
Given:
t1/2 = 3 years
18 years = 6 half lives
Solve: (1/2)number of half lives
Solve: (1/2)6
= 1/64
2) If the original mass of the isotope was 50.0 grams, how many grams remain after 18 years?
Solve:
(1/64) x 50.0 g = grams remain

32. Practice Problem #2
The half life of I-123 is 13 hr. How much of a 64 mg sample of I-123 is left after 26 hours?

33. Solution
t1/2 = 13 hrs 26 hours = 2 half lives Amount initial = 64mg Amount remaining = 64 mg x (½)2 = 16 mg

34. Nuclear Fission
Fission large nucleus breaks up 235U + 1n 139Ba + 94Kr + 3 1n
Energy

35. Fission

36. Nuclear Fusion
Fusion small nuclei combine 2H + 3H 4He + 1n Occurs in the sun and other stars
Energy

37. Learning Check Indicate if each of the following are
Fission (2) fusion
Nucleus splits
Large amounts of energy released
Small nuclei form larger nuclei
Hydrogen nuclei react
Energy

38. Solution Indicate if each of the following are Fission (2) fusion
Nucleus splits
Large amounts of energy released
Small nuclei form larger nuclei
Hydrogen nuclei react