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- 1. 7.2 Half-Life What will we learn? -What are daughter isotopes? -What is the decay curve? -What is half-life? -What are parent isotopes? -What is radiocarbon dating?
- 2. Half-Life is the time it takes for half of the mass of a substance to decay. Shows the rate of radioactive decay for different isotopes. Short half-life = Fast decay rate Knowing the half-life of an isotope allows radioisotope dating to be possible 7.2 Half-Life
- 3. A decay curve shows the decay rate for radioisotopes Graphing any isotope’s decay rate will produce the same curve, the only difference is how long the half-life is Decay Curve
- 4. The parent isotope = isotope that undergoes radioactive decay The daughter isotope = stable product of radioactive decay It may take several decays for a parent isotope to produce stable daughter isotopes The most common of these parent/daughter pairs are shown in the Common Isotope Pairs Chart These isotopes can all be used in radioisotope dating, for various dating ranges Parent & Daughter Isotopes
- 5. This is the method used to date organic material Uses the isotope carbon-14, which has a half-life of 5730 years, and decays into nitrogen-14 Can date material up to 50000 years old Radiocarbon Dating
- 6. 7.2 Quiz 1. How much of a sample of 100g of Carbon-14 will be left after 22920 years? a) 50g b) 25g c) 12.5g d) 6.25g 2. What is the daughter isotope of Uranium-235 when it decays? a) nitrogen-14 b) lead-207 c) argon-40 d) lead-206
- 7. 7.2 Answers 1. How much of a sample of 100g of Carbon-14 will be left after 22920 years? a) 50g b) 25g c) 12.5g d) 6.25g 2. What is the daughter isotope of Uranium-235 when it decays? a) nitrogen-14 b) lead-207 c) argon-40 d) lead-206
- 8. Video:
- 9. 7.3 Nuclear Reactions What will we learn? -What is a chain reaction? -What is fission? -What is fusion? -What is a nuclear equation? -What is a nuclear reaction?
- 10. Nuclear Fission The splitting of a nuclei into two smaller nuclei, subatomic particles and energy Heavy nuclei are unstable because of protons’ repulsive forces May split into smaller atoms to become stable All nuclear power generation comes from nuclear fission Nuclear waste must be stored away for hundreds of thousands of years
- 11. Nuclear Fusion The joining of two nuclei to form a larger nuclei Happens in the core of stars Requires high pressure and temperature In our Sun, hydrogen-2 and hydrogen-3 fuse into helium-4 Currently not a feasible way of generating electricity
- 12. Nuclear Reaction A reaction that changes the nucleus of an atom Gains or releases particles or energy Can release electrons, protons, neutrons, or gamma rays Small change of mass = Large change of energy
- 13. Chain Reaction One reaction starts the next reaction Reaction continues on its own Releases a large amount of energy, possibly leading to an explosion if not controlled Can be controlled by materials that absorb neutrons, such as cadmium
- 14. Nuclear Equation Sum of mass numbers on both sides of the equation must be equal Sum of charges/atomic numbers on both sides of the equation must be equal Equation for nuclear fission of uranium-235: Equation for nuclear fusion of hydrogen-2 and hydrogen-3:
- 15. 7.3 Quiz 1. What is the missing atomic mass? a) 6 b) 7 c) 14 d) 15 2. What is the missing atomic number? a) 92 b) 90 c) 93 d) 234 3. What type of radiation caused Bruce Banner to turn into the Hulk? a) Alpha b) Beta c) Gamma d) Neutron
- 16. 7.3 Answers 1. What is the missing atomic mass? a) 6 b) 7 c) 14 d) 15 2. What is the missing atomic number? a) 92 b) 90 c) 93 d) 234 3. What type of radiation caused Bruce Banner to turn into the Hulk? a) Alpha b) Beta c) Gamma d) Neutron
- 17. Video:
- 18. End

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