2. Radioisotope: an unstable isotope that spontaneously changes its nuclear structure and releases energy in the form of radiation. Isotopes Stable Radioisotopes Unstable

3. An unstable atom with a nucleus that can spontaneously disintegrate is said to be radioactive. Abundant Stable Isotopes β + decay β - decay Radioactive Isotopes These are just a few examples, there are more stable and unstable isotopes for tin!

4. Abundant All isotopes of Uranium are radioactive. None are stable.... Isotopes Stable Radioisotopes Unstable

5. How long does it take for a radioactive atom to disintegrate? How do we find out? Half-life: the average length of time it takes radioactive material to decay to half of its original mass The half life of Cobalt-60 is 5.27 years. Does that mean that it takes 5.27 years for an isotope atom to decay?

6. Example half life of Cobalt-60 is 5.27 years It takes 5.27 years for the sample to decay to half of it’s original mass 100 g50 g 81 g 69 g 50 g counting only the blue Cobalt-60 atoms

7. Example continued What if we wait another 5.27 years? 50 g It takes 5.27 years for the sample to decay to half of it’s original mass 25 g 32 g

8. Trying it out Carbon-15 has a half-life of 2.5 s. If the sample is 100g, how much carbon-15 will be remaining after 10s? Time (s)Mass of carbon-15 (g) 0100 2.550 525 7.512.5 106.25

9. Applications Which elements are used for determining the age of: - a living thing that has died - the moon or the earth Explanation together.

10. Nuclear Fission Same amount of energy in one reaction as about 7 million times as great as the energy released when the same mass of dynamite explodes.

11. Heavy water: water that contains a high level of deuterium

12. Nuclear CANDU Reactor Our focus in this course: the transformations of energy. Photo source: http://www.nucleartourist.com/type/candu.htm

13. Nuclear fission produces neutrons and thermal energy. Heavy water moderates neutrons and absorbs thermal energy. Thermal energy is transferred to the steam generator. Heavy water cools and flows back. Normal water absorbs thermal energy and vaporizes into steam. Steam pressure builds and transforms thermal energy into mechanical energy causing the turbine to turn. The electrical generator converts the mechanical energy into electrical energy.

14. Nuclear Fusion Nuclear fusion: a nuclear reaction in which the nuclei of two atoms fuse together to form a larger nucleus. Proton-proton chain CNO chain Photo source: http://en.wikipedia.org

15. Nuclear Fusion Nuclear fusion produces significantly more energy per mass of fuel than fission reactions. The only man-made fusion device to achieve ignition to date is the hydrogen bomb. Nuclear fusion occurring in stars.