1. Nuclear Physics

2. Nuclear Symbols Mass number, A (p+ + no) Element symbol
Atomic number, Z
(number of p+)

3. Balancing Nuclear Equations
Areactants = Aproducts
= (1)
= (0)
Zreactants = Zproducts

4. Balancing Nuclear Equations #2
222
226 = 4 + ____
222 Rn 86
88 = 2 + ___ 86
Atomic number 86 is radon, Rn

5. Balancing Nuclear Equations #395
= (1) + ____ 95 Y 39 39
= (0) + ____
Atomic number 39 is yttrium, Y

6. Alpha Decay Alpha production (a): an alpha particle is a
helium nucleus
Alpha decay is limited to heavy, radioactive
nuclei

7. Alpha Radiation
Limited to VERY large nucleii.

8. Beta Decay Beta production (b): A beta particle is an
electron ejected from
the nucleus
Beta emission converts a neutron to a proton

9. Beta Radiation
Converts a neutron into a proton.

10. Gamma Ray Production Gamma ray production (g):
Gamma rays are high energy photons produced in association with other forms of decay.
Gamma rays are massless and do not, by themselves, change the nucleus

11. Deflection of Decay Particles
Opposite charges_________ each other.
attract
Like charges_________ each other.
repel

12. Positron Production Positron emission:
Positrons are the anti-particle of the electron
Positron emission converts a proton to a neutron

13. Electron Capture
Electron capture: (inner-orbital electron is captured by the nucleus)
Electron capture converts a proton to a neutron

14. Types of Radiation

15. Nuclear Stability
Decay will occur in such a way as to return a nucleus to the band (line) of stability.
The most stable nuclide is Iron-56
If Z > 83, the nuclide is radioactive

16. A radioactive nucleus reaches a stable state by a series of steps
A Decay Series

17. Half-life Concept

18. Sample Half-Lives

19. STOP

20. NUCLEAR DECAY KINETICS

21. Decay Kinetics
Decay occurs by first order kinetics (the rate of decay is proportional to the number of nuclides present)
N0 = number of nuclides
present initially
N = number of nuclides
remaining at time t
k = rate constant
t = elapsed time

22. Calculating Half-life
t1/2 = Half-life (units dependent on rate
constant, k)

23. Example
Determine the amount of Rn-222 that remains after 5.0 days if the the half-life is 3.8 days and you started with 80,000 particles. No = 80,000 particles k = day-1 N = ? First find decay constant. k = ln2 / t1/2

24. Example 2
Determine the activity of Rn-222 that remains after 7.0 days if the the half-life is 3.8 days and you started with 285 counts/min.
Ao = 285 counts/min
k = day-1
N = ?
First find decay constant. k = ln2 / t1/2

25. Example 3
Determine the percentage of Rn-222 that remains after 9.0 days if the the half-life is 3.8 days.
No = ??? particles
k = day-1
N = ?
First find decay constant. k = ln2 / t1/2

26. Nuclear Fission and Fusion
Fusion: Combining two light nuclei to form a heavier, more stable nucleus.
Fission: Splitting a heavy nucleus into two nuclei with smaller mass numbers.

27. Energy and Mass
Nuclear changes occur with small but measurable losses of mass. The lost mass is called the mass defect, and is converted to energy according to Einstein’s equation:
DE = Dmc2
Dm = mass defect
DE = change in energy
c = speed of light
Because c2 is so large, even small amounts of mass are converted to enormous amount of energy.

28. Example
Calculate the mass defect and energy released during this typical fission reaction.  + +
g g g 4 x g
g g
DE = Dmc2 = kg x 3.0 x 108 m/s
DE = x 107 J

29. Fission

30. Fission Processes
A self-sustaining fission process is called a chain reaction.

31. A Fission Reactor

32. Fusion