2. NUCLEAR CHEMISTRY 1

3. Isotopes-Review  Isotopes are atoms of the same element that have the same # of protons but different # of neutrons or mass. X Atomic mass Atomic number 2

4. NATURAL RADIOACTIVITY 1- Spontaneous Decay- emit energy without absorption of energy from an out side source. 2- Elements with atomic # greater then Bi 83 are unstable and are radioactive. 3- Isotopes that are unstable have an unstable ratio of protons and neutrons greater then 1:1 3- TRANSMUTATION- changes to the nucleus of an element 3

5. TYPES OF EMISSIONS 1- ALPHA DECAY: -Identified as helium nuclei (2 protons & 2 neutrons) - Both the mass & charge are balanced. - Total atomic number of reactants = products 4

6. BETA DECAY 1- Have the same charge and mass as electrons 2- Electrons are ejected at high speeds from radioactive isotopes. 3- A neutron transformed into a proton with creation of an electron. 5

7. POSITRON EMISSION 1- Same mass as electrons, but + change (NOT -) 2- When positron electrons meet, they annihilate each other, producing large amounts of energy. 6

8. GAMMA RAYS 1- High energy electromagnetic waves 2- No mass, not considered particles. 3- Have penetrating abilities similar to X-Rays 7

9. CHARACTERISTCS OF ALPHA, BETA, AND GAMMA EMISSONS 8

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11. HALF-LIFE 1- Radioactive isotopes- decay or breakdown at different or characteristic rates. 2- Half-life: time interval required for half the sample to disintegrate 3- EX: iodine-131 100grams half-life = 8 days -0 days = 100g -8 days = 50g -16 days = 25g - 24 days = 12.5 g 4- FIND HALF-LIFE REFERENCE TABLE N - IF NOT GIVEN START WITH ZERO TIME!!! 10

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13. Nuclear Reactions 1- Nuclear Reaction- change in the nucleus of an atom with a release of large amounts of energy. 2- Nuclear reactions include: -Spontaneous transmutation - artificial transmutation - fission - fusion 12

14. Artificial Transmutations 1- Artificial Transmutation: bombarding a stable atom with particles, nuclei become unstable and isotopes are formed. 1- Creates unstable fluorine atom that immediately decays to oxygen-17 by releasing a proton 2- Most artificial transmutations occur in particle accelerators. 3- Elements on the Periodic Table beyond uranium ( 92 U) are artificial transmutations. 13

15. FISSION 1- Fission: nuclear reaction in which a heavy, unstable nucleus is split into 2 mid-size nuclei. - it releases 1 or more neutrons and a large amount of energy! 2- Controlled reaction in nuclear power plants-produces great amounts of energy. -Uncontrolled reaction= nuclear weapons 14

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17. FUSION 1- FUSION: When 2 or more light nuclei combine to form a single nucleus of greater mass. - Fusion releases more energy then Fission!!! - Hydrogen bomb- created by FUSION!!! - FUSION REACTIONS: high temperatures, over 5 million K and high pressure! 16

18. 1- The mass numbers and atomic numbers in a nuclear reaction are balance, the total mass of products are less. 2- In a nuclear reaction- the mass lost is converted to ENERGY! 3- Albert Einstein’s equations E = mc 2 -the energy produced is equal to the mass lost - a tiny fraction of the mass is converted to a large amount of energy 4- LAW OF CONSERVATION OF MASS-ENERGY- combines both the law of conservation of mass + the law of conservation of energy! 17

19. Benefits and Risks of Radioactivity 1- NUCLEAR POWER: - produces electricity by combustion of fossil fuels - MAJOR RISK: storage of highly radioactive waste products- long half-lives -FISSION- produces electricity at low cost and does not produce CO 2 - Greenhouse effect. Fission produces energy released by uranium-235 -FUSION- produces more energy, Hydrogen is abundant and products are not radioactive 18

20. Radioactive Dating 1- Useful is determining the age of an object by measuring the amount of radioactive isotope that remains in a sample. 2- Age of fossils- determined from the ration of C-12 & C-14 contained in the sample. 19

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22. Medical Diagnosis and Treatment 1- Isotopes- used for diagnosis of diseases and treatments - used in diagnosis of heart, lung, liver, spleen, & bone - Iodine-131 used for Thyroid disorders- short half-life - Cancer treatments- radiation uses Cobalt-60- emits gamma rays that destroy tumors - Overexposure can cause mutations in DNA and destroy health tissue. 21

23. Radioactive Tracers 1- Used in chemical research. - Identifies and detects intermediate products along the reaction pathway of chemical reactions 22

24. Food Safety & Preservation -Food irradiation kills insects, mold, & bacteria that cause illness! -- Kills salmonella and E-coli bacteria 23

25. Industrial Measurement -Radiation is used to measure the thickness and physical dimensions of products - Used to measure and detect structure flaws in metal parts 24