1. Nuclear Fission and Fusion Nuclear Radiation Today Ms. Miranda Mack Physical Science Honors 5 th pd. March 2, 2009

2. Nuclear Forces  The stability of a nucleus depends on the nuclear forces that hold the nuclear together.  The forces exist between the protons and neutrons.  The strong nuclear force causes the protons and neutrons to attract one another.

3. Instability of the Nucleus  Having too few or too many protons or neutrons causes a nucleus to be unstable. –Nuclei with an atomic number greater than 83 are always unstable –decay, producing large amounts of radiation

4. Nuclear Fission  Splitting heavier nuclei into light nuclei  The reaction releases large amounts of energy  Einstein’s theory of relativity is: E=mc 2 –Energy = mass x the speed of light 2 –Matter can be converted into energy and energy to matter

5. Continued…  The mass of a nucleus is less than the masses of the individual particles that make up the nucleus.  This “missing” mass is called the mass defect.  What happens to the missing mass? –It changes into energy

6. Nuclear Fission continued…  Neutrons released by fission can start a chain reaction –A continuous series of nuclear fission reactions –This energy can be controlled and can be used to generate electricity –Critical mass- the minimum mass of a fissionable isotope that provides the number of neutrons needed to sustain a chain reaction

7. Nuclear Fusion  Energy can also be rendered when lighter nuclei combine to form heavier nuclei  Stars, particularly the sun are produced by nuclear fusion.  Large amounts of energy are needed to produce a fusion reaction.

8. Radiation  Background radiation comes from natural sources and is everywhere  Benefits include smoke detectors, X rays, CT, PET, radiotherapy, radioactive tracers, and radioisotopes  Risks can result from high exposure from radiation: cancers, radiation sicknesses

9. Assignment  Pg. 308-309 # 1-10, 17-19, 21-23 –Due: Wednesday, March 4, 2009  End of exam material- study guide available on Tuesday, March 3, 2009  Wednesday- LAB  Thursday- more review with mentors  Friday- Exam 5