3. Some elements have atoms which are unstable. These atoms spontaneously transmutate from one element to another. These types of transmutations include beta decay, electron capture and alpha decay. Alpha decay involves the emission of a helium nucleus. + 90 231 Th

4. Different radioactive isotopes decay at different rates. If 100 g of a radioactive material decays for 10 years and 50 g remains this substance is said to have a half life of 10 years. 5 y After 10 y only 50 g remain If 200 g of a radioactive material with a half-life of 5 years, is left to decay for 10 years how much of the original material is left? 200 g -------> 100 g -------> 50 g

5. If 200 g of a radioactive material with a half-life of 5 years, is left to decay for 10 years how much of the original material is left? 200 g -------> 200 g

6. If 200 g of a radioactive material with a half-life of 5 years, is left to decay for 10 years how much of the original material is left? 200 g -------> 100 g 100 g left after 5 years

7. If 200 g of a radioactive material with a half-life of 5 years, is left to decay for 10 years how much of the original material is left? 200 g -------> 100 g -------> 50 g 50 g left after 10 years

8. If 200 g of a radioactive material with a half-life of 5 years, is left to decay for 10 years how much of the original material is left? 200 g -------> 100 g -------> 50 g ----> 25g 25 g left after 15 years

9. Show the decay sequence for 512 g of a substance with a half-life of 25 da. 512 g

10. Show the decay sequence for 512 g of a substance with a half-life of 25 da. 256 g 512 g ---> 256 g 25 da

11. Show the decay sequence for 512 g of a substance with a half-life of 25 da. 128 g 512 g ---> 256 g ---> 128 g 25 da Total - 50 da

12. Show the decay sequence for 512 g of a substance with a half-life of 25 da. 64 g 512 g ---> 256 g ---> 128 g ---> 64 g 25 da Total - 75 da

13. Show the decay sequence for 512 g of a substance with a half-life of 25 da. 32 g 512 g ---> 256 g ---> 128 g ---> 64 g ---> 32 g 25 da Total - 100 da

14. Show the decay sequence for 512 g of a substance with a half-life of 25 da. 16 g 512 g ---> 256 g ---> 128 g ---> 64 g ---> 32 g 25 da Total - 125 da 16 g 25 da

15. Show the decay sequence for 512 g of a substance with a half-life of 25 da. 512 g ---> 256 g ---> 128 g ---> 64 g ---> 32 g 25 da Total - 150 da 16 g 25 da 8 g 25 da

16. Show the decay sequence for 512 g of a substance with a half-life of 25 da. 512 g ---> 256 g ---> 128 g ---> 64 g ---> 32 g 25 da Total - 175 da 16 g 25 da 4 g 8 g 25 da 4 g 25 da

17. Show the decay sequence for 512 g of a substance with a half-life of 25 da. 512 g ---> 256 g ---> 128 g ---> 64 g ---> 32 g 25 da Total - 200 da 16 g 25 da 2 g 8 g 25 da 4 g 25 da 2 g 25 da

18. Show the decay sequence for 512 g of a substance with a half-life of 25 da. 512 g ---> 256 g ---> 128 g ---> 64 g ---> 32 g 25 da Total - 225 da 16 g 25 da 1 g 8 g 25 da 4 g 25 da 2 g 25 da 1 g 25 da

19. If U-235 has a half-life of 7.1 x 10 8 y. How many years would it take 32 g to decay to 2 g? 32 g --> 16 g --> 8 g --> 4 g --> 2 g 4 half lifes 2.84 x 10 9 y. Cs-136 has a half-life of 13 da. If 1024 g was left to decay for 65 da how much of the original material would be left? 65/13 = 5 hl 1024 g -> 512 g -> 256 g -> 128 g -> 64 g -> 32 g or 1024 g x (1/2) 5 = 32 g

20. To find the quantity of material remaining use this formula Mass remaining = Original Mass x 1 2 # of Half-lives Pb-212 has a half-life of 10.6 h. If 12.5 g of Pb-212 is left for 84.8 h how much of the original material is left? Mass remaining = Original Mass x 1 2 # of Half-lives 12.5 g x (0.5) 84.8/10.6 = 0.0488 g