1. Radioactivity & Nuclear Rxns Chapter 6.1 & 6.2

2. Nuclear Radiation  Comes from an unstable nucleus  Radiation can be released as either… –Particles –or Energy (such as electromagnetic radiation) –or Both

3. Types of Radiation  Ionizing Radiation causes atoms to become charged (ions) –Alpha & Beta Particles –Neutron Emission –High Freq. Electromagnetic Radiation (x-rays)  Nonionizing Radiation –Visible Light –Infrared –Microwaves and Radio waves

4. Nuclear Decay When an unstable nucleus emits an alpha or beta particle… …the number of protons or neutrons changes. This means that the identity and/or the mass of the atom will change also.

5. Radioactive Decay Rates  Decay is spontaneous and random… –when observing ONE atom.  When observing a large sample of material the decay is no longer random.

6. Radioactive Decay Rates  Half-life –This is the time required for half of a sample to decay.  Examples –Uranium-238  4.47 x 10 9 years –Potassium-40  1.28 x 10 9 years –Carbon-14  5730 years –Iodine-131  8.1 days –Hafnium-156  0.025 seconds

7. Review of the Nucleus  Contents –Protons –Neutrons  Active Forces –Repulsions –Strong Nuclear Force

8. Nuclear FISSION  Splitting a nucleus into smaller fragments.  This also releases neutrons and energy.

9. Nuclear Fission (con’t)

10.  Hahn and Strassman conducted experiments on fission in 1939  They found the mass before and after the reaction was not equal. –Where did the mass go? –Remember the Laws of Conservation?  Mass and Energy were found to be equivalent!!!

11. There is an equation for this… IT’S WRITTEN AS… E = mc 2 c = speed of light

12. Nuclear Fission (con’t) How much energy is converted from mass? 5 lb. of mass, converted all into energy is equal to 16 million TONS of TNT Fortunately, most objects are stable and never spontaneously change into energy!

13. Nuclear FUSION  Combining two light nuclei into a heavier nuclei  This also releases energy. This process takes place naturally in stars. It’s how our elements were formed. Scientists are trying to make it work in a lab.

14. Nuclear Fusion (con’t)

15. Animations Fission Fusion