1. Nuclear Transformation
28.2

2. Stability Stability comes from the neutron to proton ratio
Below the atomic number 20 the ratio is 1 (equal)
Above 20, more neutrons than protons, ratio is 1.5
85 % of all nuclei are unstable

3. Decay Some nuclei have to many neutrons
They decay by turning neutron to a proton and emit a beta particle
Beta decay

4. Decay Other nuclei are unstable because they have to few neutrons
Become stable by converting a proton to a neutron
This creates a positron

5. Decay All nuclei with atomic number greater than 83 are radioactive
They have too many neutrons and too many protons
Most emit alpha particles.

6. Decay Mass is not conserved
Lost mass is converted to energy (radiation)

7. Half Life
Time that is required to decay half of radioisotope nuclei to product
After 1 half life, half of radioactive atoms have decayed to a new element

8. Half Life # of ½ lives= Total Time half life length
Scientists use half life to determine age of ancient artifacts
Carbon dating- known time to convert isotope of C-14 to N-14
# of ½ lives= Total Time
half life length
Sample(final)= Sample(initial) x (1/2)number of half lifes

9. Half Life
Read pg
How many half-lives of carbon 14 is 75,000 years?
What percentage of the carbon 14 remains after this number of half lives?

10. Transmutation Conversion of one element to another
Radioactive decay is one way transmutation occurs
Also occurs when nucleus is bombarded by high energy particles
protons, neutrons or alpha particles

11. Transmutation
Ernest Rutherford 1919 performed earliest artificial transmutation
What element is named after him?
Explain his experiment.

12. Transmutation Rutherford lead to finding proton
Chadwick’s transmutation in 1932 lead to finding neutron
Read pg. 844 Link to Physics

13. Transuranium elements
Atomic number 92 and above
All go thru transmutation
None occur in nature
All are radioactive

14. Transuranium elements
First artificial elements made in 1940
18 more have been made, atomic numbers 95 through 112 and more to come

15. Discussion
Alchemists tried for years to turn common metals in to precious metals
No chemical reaction can achieve their goal
Thru transmutation you can