1. Natural Radioactivity – Unstable Nuclei Emit Radiation
Spontaneous nuclear change to attain good n/p ratio.
Form a new kind of atom.
Each isotope or nuclide decays in a certain manner to get a better n/p ratio. The decay mode is named for the particle emitted. See Table N.

2. Balancing Nuclear Equations

3. Nuclear Equations Describe the decay process.
reactant or starting side (left)  product or ending side (right).
 separates two sides

4. Nuclear Equations - tasks
Have to identify type (out of 4)
Have to balance to find 1 unknown term.

5. Natural Transmutation – I.D.
1 term on the reactant side – starting isotope.
2 terms on the product side – ending isotope and emitted particle.
Type of particle emitted is characteristic of the isotope – look up particle in Table N.

6. Nuclear Equations
Use conservation of atomic number & conservation of mass number to balance them.
Mass number = left superscript.
Atomic Number = left subscript.

7. Writing Equations Write the equation for the decay of Thorium-232.
Use Table N to find the decay mode:
Write the initial equation: 
232Th  4He + X 90 2
 Have to figure out what element it turned into.

8. Alpha decay, Th-232
232Th  4He + YX 90 2 Z

9. Alpha decay, Th-232 232 = 4 + Y so Y = 228
232Th  4He X Y Z 90 2
Conservation of Mass Number:
The sum of the mass numbers on the left side must equal the sum of the mass numbers on the right side.

10. Alpha decay, Th-232 so Z = 88 90 = 2 + Z
232Th  4He + 228X 90 2 Z
90 = Z
so Z = 88
Conservation of Atomic Number:
The sum of the atomic numbers on the left side must equal the sum of the atomic numbers on the right side.

11. Alpha decay, Th-232 232Th  4He + 228X 90 2 88 Use the P.T. to find X:
X = Ra
232Th  4He + 228Ra 90 2 88

12. Nuclear Equations
If there is only 1 unknown term you can figure out what it is.
Doesn’t matter which one isn’t known.
Don’t forget – you can look up the decay mode in Table N. Decay mode means what particle is emitted.

14. Write an equation for the  decay of Am-241
so Y = 237
241 Am  4He + YX Z 95 2
so Z = 93
95 = Z
What’s X?
X = Np

15. Write equations for α decay
218Rn + 4He
222Ra 
208Po 
256Lr  88 86 2
204Pb + 4He 84 82 2
252Md + 4He
103
101 2

16. Writing equations for α decay
231Pa 
225Ac 
211Fr 
185Au 
227Ac + 4He 91 89 2
221Fr + 4He 89 87 2
207At + 4He 87 85 2
181Ir + 4He 79 77 2

17. α decay
229Th + 4He
233U 
149Gd 
232Th 
175Pt 
237Np  90 2 92
145Sm + 4He 2 62 64
228Ra + 4He 88 2 90
171Os + 4He 76 78 2
233Pa + 4He 91 93 2

18. α decay 234Th  144Nd  146Sm  151Ho  192Pt  4He + 230Ra 90 88 2
4He Ce 60 2 58
4He Nd 62 2 60
4He Tb 67 2 65
4He Os 78 2 76

19. Radioactive Decay Series
Sometimes 1 transmutation isn’t enough to achieve stability.
Some radioisotopes go through several changes before they achieve stability (and are no longer radioactive).

20. Decay series for U-238.

21. Decay series for Thorium-232

22. Decay series for U-235

23. Alpha Decay
238 =
238 =
92 =

24. Positron Emission
1p  1n + 0e 1 +1

26. Beta minus emission
1n  1p + 0e 1 -1

27. 14C  14N + 0e 6 7 -1
18F  18O + 0e 9 8 +1

28. How does the mass number or atomic number change in  (or  or ) decay?
Just go to Table N, find an isotope that decays by alpha decay, write the equation, and see how the mass number (or atomic number) changes.
226Ra  4 + X so X has to be 222X
X is Ra The mass number decreases by 4 and the atomic number decreases by 2. 2 86 88