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Nuclear Physics.

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Presentation on theme: "Nuclear Physics."— Presentation transcript:

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 #3
95 = (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


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