1. Radioactive Decay

2. Radioactive materials decay from the “Parent” material
into the “Daughter Product”.
Daughter Product
Original
“Parent” Material

3. Some atoms in the parent are isotopes
These atoms have a different number of neutrons than protons
They are unstable
As isotopes decay to stable daughter energy is released

4. You’ll never know which atoms will decay...

6. … or when ...

7. But one thing we do know...

8. ...is that it always takes the same
amount of time for half to disappear.
(8 atoms)

19. Radioactive Decay Parent – unstable Daughter – stable
Half-life is the time required for HALF of the atoms of the unstable parent to decay to stable daughter

20. Radioactive Decay Data
Parent
Daughter
Half-live years
Carbon 14
Nitrogen 14
5,700
Potassium 40
Argon 40
Calcium 40
1.3 billion
Uranium 238
Lead 206
4.5 billion
Rubidium 87
Strontium 87
49 billion

21. Each half-life, the amount of atoms gets cut in half.

22. Since you don’t know how many atoms you started with, a ratio between parent to daughter will tell you how many half-lives have gone by.
100% parent
0% daughter
0 half lives

23. One half-life.
50% parent
50% daughter
1 half-life

24. Two half-lives.
25% parent
75% daughter
2 half-lives

25. Three half-lives.
12.5% parent
87.5% daughter
3 half-lives

26. Four half-lives.
6.25% parent
93.75% daughter
4 half-lives

27. Don’t worry about the last atom
Don’t worry about the last atom. You start with so many trillions that you never really get there. (It will just decay and then they’re all gone.)

28. Shape of curve similar for each radioactive isotope

29. Half Life Continues indefinitely Random and spontaneous
Not affected by temperature or pressure
Not affected by mass or volume of parent