1. Nuclear Chemistry Unit 10

2. Radioactivity The spontaneous emission of radiation by an unstable atomic nucleus. Discovery Henri Becquerel-1896 Worked with phosphorescent uranium (thought to be x-rays) Marie and Pierre Curie were the one’s to actually name the process as radioactivity

3. Nuclear Notation

4. Radioactive Decay Alpha Decay ( α ) Alpha particles are helium nuclei consisting of 2 protons and 2 neutrons Does not penetrate deeply into matter. Loss of 2p and 2n results in the daughter atom being two elements before the parent atom. Example:

5. Radioactive Decay

6. Gamma Decay ( γ) Gamma ray is a high energy form of electromagnetic radiation without a mass or charge. Need thick blocks of lead or concrete to stop. Normally does not occur alone but accompanies other forms of decay.

8. Practice Decay of U-238 to Pb-206: a,b,b,a,a,a,a,a,b,b,a,b,b,a

9. Detecting Radioactivity Detects ionizing radiation

10. Radioisotope Dating Half-life – the time it takes for half of a given amount of a radioactive isotope to undergo decay. Carbon-14 dating 1 in a million carbon atoms Decays to nitrogen-14 after death Half life is 5,730 years Other isotopes used for dating Potassium-40 (half life = 1.25 billion years) Uranium-238 (4.5 billion years) Rubidium-87 (48 billion years)

11. Einstein and Energy First scientist to realize the amount of potential energy available in matter. E=mc 2 E=Energy m = mass c= speed of light (671,000,000 mph)

12. Nuclear Fission The splitting of an atomic nucleus into two or more smaller fragments, accompanied by a large release of energy. Uranium nuclei are split by bombarding with a neutron.

13. Nuclear Fission Subcritical mass – If there is not enough fissionable material present to sustain a chain reaction (super)critical mass – If there is enough fissionable material to sustain a chain reaction. (exponential and dangerous if not controlled)

14. Nuclear Reactor

15. Elements Used Uranium-235 is the main radioactive element used in a fission reactor. Plutonium-239 can also be used Breeder reaction Fission Bombs

16. Nuclear Fusion Process of combining two or more nuclei to form a larger nucleus. Process that produces energy in stars. Most typical fusion reaction is when hydrogen atoms fuse to make helium.

17. Fusion process Deuterium (D) – A hydrogen atom with a mass number of 2. Tritium (T) – A hydrogen atom with a mass of 3.

18. Radioisotopes and Health Tracers – used in the body to find abnormalities. Act like normal isotopes Radiation can be detected Iron-59 Used to show circulatory system Environment Sulfur-35 used to trace pesticides from field to streams

19. Sources of Radiation Background radiation- caused by radioactive elements in rocks, fabrics, food, etc.

20. Health Problems Radiation can knock electrons creating ions. Damages cell processes Dividing cells pass down damaged DNA Waste can take thousands of years to decay

21. Measuring Radiation Gray – equal to the transfer of 1 joule of energy in the form of radiation to 1 kg of living cells. Sievert (Sv)- equal to 1 gray multiplied by a factor that take tissue absorption into account.

22. Radon and the Home Radon-222 can cause lung cancer. changes into isotopes of polonium and lead. Po and Pb isotopes attach to dust particles and enter lungs. Emit alpha particles which damage cells. Radon is dense and normally accumulates in basements Exhaust fan and sealing large cracks