1. Nuclear Reactions

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When an atom is stable, the strong force in the nuclei is able to keep the nucleus permanently together.

3. Nuclear Reactions Radioactivity-
However, when the strong force is not large enough to hold a nucleus together tightly, the nucleus can decay and give off matter and energy. The process of nuclear decay is called radioactivity.

4. NUCLEAR FISSION AND FUSION

5. Nuclear Reactions Nuclear Fission-
The process of splitting a nucleus into 2 nuclei with smaller masses. Fission means to “divide”.
Only the elements Uranium and Plutonium may undergo nuclear fission.
Nuclear fission is similar to the game of pool.

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A chain reaction is an ongoing series of fission reactions. Billions of reactions may occur each second resulting in the release of tremendous energy.

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This chain reaction led to the formation of the Atomic bomb.

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17. Nuclear Reactions Nuclear Fusion-
2 nuclei with low masses are combined to form one nucleus of larger mass. Hot temperature is required. Fusion fuses atomic nuclei together, and fission splits nuclei apart.
Occurs mostly in the sun and stars.
Occurs in Hydrogen bomb

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24. Nuclear Reactions Nuclear reactions have advantages and disadvantages.
-Tracers in medicine
-Treatment of cancer
-Energy production
-Environmentally safe*

25. Nuclear Reactions Nuclear Reactions in Medicine-
If you were going to meet a friend in a crowded public area, you might tell them to wear a red hat. Scientist use this technique to mark an atom in a large group of atoms. They place a radioactive atom in it to be found more easily. This atom is called a tracer.

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Tracers follow where a particular molecule goes in your body or to study how a particular organ functions.
Examples: Iodine tracers in the thyroid

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Treating cancer with radioactivity is another example of using nuclear radiation in medicine.

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30. Nuclear Reactions Nuclear Energy-
Nuclear power plants generate electricity using the energy release in nuclear fission.
The reactor core in an energy plant produces the equivalent energy released in 3 million kg of coal.
An advantage of nuclear energy is that it is environmental friendly since it does not require the burning of fossil fuels.

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32. Nuclear Reactions Disadvantages- -Nuclear waste
-Risk of release of radioactivity
-Nuclear weapons

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A disadvantage of nuclear energy is nuclear waste. Nuclear waste is any radioactive by-product that results when radioactive materials are used.
Another disadvantage is the risk of the release of radioactivity (1986 Chernobyl, Ukraine).

34. Nuclear Reactions Chernobyl-
On April 26, 1986, the fourth reactor of the Chernobyl Nuclear Power Plant exploded at 01:23 AM local time which had caused the biggest nuclear disaster in history of the mankind.

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Radioactive decay is when an unstable nucleus spontaneously disintegrates into a smaller, more stable nucleus. Radioactive decay releases energy and nuclear radiation.

45. Nuclear Reactions Alpha emission (α)
Alpha emission results when a very heavy nucleus emits 2 protons and 2 neutrons (Helium) at the same time.
2. An alpha particle is represented by the symbol:
Ex:

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47. Nuclear Reactions Beta emission (β-)
Beta emission results when a nucleus converts a neutron into a proton and an electron, then emits the electron from the nucleus.
2. A beta particle is represented by the symbol:

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Beta emission (β-)

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50. Nuclear Reactions Positron emission (β+)
1. Positron emission results when a nucleus converts a proton into a neutron and emits a positron from the nucleus.
2. A positron has the same mass as an electron, but has a positive charge.
3. A positron is represented by the symbol:
Ex:

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Positron emission (β+)

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53. Nuclear Reactions Electron capture (e-)
1. Electron capture is when a nucleus captures an electron, combines it with a proton, and forms a neutron.
2. An electron (e-) is represented by the symbol:
Ex:

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55. Nuclear Reactions Gamma emission (γ)
1. Gamma rays are high energy waves emitted from the nucleus immediately following other types of decay.

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A measure of the time required by the nuclei of an isotope to decay is called the half-life.
The half-life of a radioactive isotope is the amount of time it takes for half the nuclei in a sample of the isotope to decay.
Example- carbon-14 dating

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