1. Reactions involving the nucleus of the atom.
Ch. 25 Nuclear Chemistry
Reactions involving the nucleus of the atom.

2. Radiation
Radiation: penetrating rays and particles emitted by a radioactive source.
Radioisotopes: radioactive isotopes
Why is an atom radioactive?
The nucleus is unstable. Wrong ratio of p+:n0
Nuclear forces v. Electromagnetic Repulsion

3. Nuclear Stability Graph

4. Types of Radiation
Alpha: Helium nucleus emitted from nucleus. Results in less p+ and n0
Beta: High speed electron ejected from the nucleus (HUH?)
n0  p+ + e-
Gamma: high energy photon (hyper x-ray)

5. Summary of Radiation

6. How far will it go?

7. Alpha Decay

8. Beta Decay

9. Gamma Radiation

10. Gamma Ray on Electromagnetic Spectrum

11. 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

12. 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.

13. 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

14. 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.

15. 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.

16. 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

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