1. Warm - Up
Using the alpha decay complete the following:
261104Rf 
24797Bk 
Using beta decay complete the following:
Fm 
24796Cm 

2. Element Quiz - 3
Which element has an atomic number of 30? How many neutrons this element has?
Write down the mass number, number of protons and number of neutrons for Iron?
Which element has 25 protons, and 30 neutrons?
Write down the symbol for the element Copper. Mark its atomic number and mass number with its symbol?
Which element has the symbol ‘V '?

3. Nuclear Stability
There are about 1500 different known nuclei (total isotopes)
Only 264 of these are stable
Stability depends on the ratio of neutrons to protons

4. Half-Life ( t½ )
Every radioisotope has a characteristic rate of decay
Half Life- time required for half of the atoms of the radioisotope to decay to its stable product

5. One half-life  1 / 2 radioactive remains
Two half-lives  1 / 4 radioactive remains
Three half-lives  1 / 8 radioactive remains

6. Half-life can be as short as a fraction of a second or as long as several million years
Many artificially produced radioisotopes have very short half-lives
Ex: 137N  136C+ 0–1e ; t1/2= 10 min

7. Half Life Diagram

8. Half-Life Problems
Element X has a mass of 300 g and a Half- life of 10 years. How many grams will remain after 40 years?

9. Half-Life Problems
Sodium-24 has a half-life of 15 hours. How many grams of sodium-24 will remain in an g sample after 60 hours?

10. Half-Life Problems
The half life of iodine-125 is 60 days. What fraction of iodine-125 nuclides would be left after 360 days?

11. Half-Life Problems
The half life of radium-226 is 1602 years. What fraction of a sample radium-226 would remain after 9612 years?

12. Half-Life Problem
After 42 days, a 2.0-g sample of phosphorus-32 contains only 0.25 g of isotope. What is the half-life of phosphorus-32?

13. Warm up
The half-life of Zn-71 is 2.4 minutes. If one had g at the beginning, how many grams would be left after 7.2 minutes has elapsed?
Os-182 has a half-life of 21.5 hours. How many grams of a 10.0 gram sample would have decayed after exactly three half-lives?

14. Nuclear Fission
When you bombard certain nuclei with neutrons, you can cause them to split into two smaller nuclei
Fissionable atoms are usually large stable radioactive nuclei

15. Fission chain reactions
When the unstable elements split into two smaller elements, they also release more neutrons which can cause more fission reactions to occur

16. Fission and Energy
Fission releases massive quantities of energy
Fission of 1 kg of U-235 releases the same amount of energy as 20,000 tons of dynamite

17. Uses of fission
Atomic bombs start through uncontrolled fission chain reactions
Nuclear reactors use controlled fission reactions

18. Nuclear Reactors
In nuclear reactors, fission occurs and the energy produce is used to heat water to steam
This steam then turns a turbine resulting in the generation of electricity

19. Nuclear Reactors
A sample of U-235 is bombarded with a neutron which begins a chain reaction resulting in the release of additional neutrons leading to more fission reactions
Fission reactions are controlled in two ways:

20. Nuclear Reactors & Controls
Neutron moderation- slow down the neutrons so that they can be used to keep the reactions going

21. Nuclear Reactors & Controls
2) Neutron absorption- neutrons are trapped before striking fissionable atoms which decrease the amount of slow neutrons

22. Nuclear Fusion
Fusion occurs when two nuclei combine to produce a nucleus of a heavier mass
Example- The sun
4 11H e  42 He + energy
Reactions occur at 40,000,000 ºC

23. Benefits of Fusion
Inexpensive fuels and readily available
Most products are not radioactive

24. Problems creating Fusion
The only time we have been able to reach the temperatures to initiate fusion is by using an atomic bomb
Also, at those temperatures matter exists in the plasma state. It is difficult to contain these types of reactions

25. Used to diagnose diseases Used to treat cancers
Medical uses Project
Use the internet, books, etc. to find out how nuclear chemistry is being used in the medical field.
Examples:
Used to diagnose diseases
Used to treat cancers

26. Half Life
Fluorine-21 has a half life of approximately 5 seconds. What fraction of the original nuclei would remain after 1 minute?
Iodine-131 has a half life of 8 days. What fraction of the original sample would remain at the end of 32 days?
If 20.0 g of a radioactive isotope are present at 1:00 PM and 5.0 g remain at 2:00 PM, what is the half life of the isotope?