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Nuclear Fission and Fusion Chapter 7.2 Mrs. Chilton.

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Presentation on theme: "Nuclear Fission and Fusion Chapter 7.2 Mrs. Chilton."— Presentation transcript:

1 Nuclear Fission and Fusion Chapter 7.2 Mrs. Chilton

2 Nuclear Stability Some elements have isotopes that are stable, while others are unstable and radioactive –Example: C-12 -> stable –C-14 -> unstable, radioactive, gives off beta particles Depends on nuclear forces holding nucleus together

3 Strong Nuclear Force How do like charges act? They repel! So, why does the nucleus with so many p+ stay together? Strong nuclear force – stronger force than electric repulsion, but only over a short distance

4 Neutrons & Stability Neutrons add to the stability of a nucleus They have no charge, so they do not repel Too many or too few neutrons leads to decay All nuclei with 83 or more protons are unstable

5 Fission When a nucleus splits into two or more smaller fragments Neutrons and energy are released

6 Fission -> Chain Reaction One neutron can split the nucleus of an atom As that nucleus undergoes fission, it releases more neutrons which can strike nearby atoms, causing them to split This can cause a chain reaction

7 Nuclear Chain Reaction

8 Uncontrolled chain reactions This principle is used in nuclear bombs Two or more masses of U-235 are contained in bomb surrounded by powerful explosive When detonated, fission chain reaction occurs releasing LARGE amount of energy which causes devastation to environment and life forms Fortunately, concentration of U-235 in nature is too low to start a chain reaction, most is more stable form of U-238

9 Controlled Chain Reaction Not all neutrons released in a fission reaction succeed in triggering fission reaction Materials that absorb neutrons can be used to slow chain reaction Concept is used in nuclear power plants to generate energy

10 Nuclear Reactor

11 Fusion Energy can also be obtained when two lighter nuclei fuse together to form a larger nucleus In stars, including our sun, energy is produced when hydrogen nuclei undergo fusion and release TREMENDOUS amounts of energy

12 Fusion in the Sun Multi-step process where two different isotopes of hydrogen fuse together to form a helium nucleus and energy in form of gamma rays

13 Dangers of Nuclear Radiation Changes structure of hemoglobin Changes structure of macromolecules in body – health is affected Particles ingested through food can damage linings of organs Destroys bone marrow Lung cancer (Radon gas) Genetic mutation

14 Beneficial Uses of Nuclear Radiation Smoke alarms –produce alpha particles to create electric current Controlled doses are used to treat some cancers – beams of gamma rays Radioactive tracers Nuclear power – much less pollution, more efficient (waste must be dealt with, though)

15 Radioactive Waste Disposal

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