Radioactivity

1. 1 Radioactivity Clip

2. 2 1 . Differentiate among alpha and beta particles and gamma radiation . 2 . Differentiate between fission and fusion . 3 . Explain the process half-life as related to radioactive decay . 4. Describe nuclear energy , its practical application as an alternative energy source , and its potential problems.

3. 3 Radioactivity is the spontaneous disintegration of atomic nuclei. The nucleus emits α particles, ß particles, or electromagnetic rays during this process. After decaying, radioactive atoms “change” into other atoms Clip

4. Why does the atom emit radiation? the nucleus of an atom attempts to become more stable In some instances, a new element is formed called an isotope. The rate of Radioactive decay is described in half-lives. 4

5. Energy is released during radioactive decay 5

6. 6 Types of Nuclear Radiation • When an unstable nucleus decays, particles and energy are given off from the decaying nucleus. • α and β radiation is in the form of particles • γ radiation is in the form of waves-kind of like light but higher frequency

7. 7 Nuclear Decay 2 protons & 2 neutrons Neutron decays into a proton

8. Alpha particles consist of two protons and two neutrons, identical to the nucleus of a helium atom. A sheet of paper or a person’s surface layer of skin will stop them. Alpha particles are only considered hazardous to a person’s health if they are ingested or inhaled 8

9. Beta particles are electrons emitted from the nuclei of many fission products. 10 • They can be stopped by clothing or a few centimeters of wood. • They are considered hazardous mainly if ingested or inhaled, but can cause radiation damage to the skin. • Unstable Neutron decays into a proton.

10. Gamma rays are a form of electromagnetic radiation Occurs when an unstable nucleus emits electromagnetic radiation. They penetrate matter easily and are best stopped by water or thick layers of lead or concrete. Gamma radiation is hazardous to people inside and outside of the body. 12

11. 13

12. 14 • Biological Effects of Radiation: • Ionizing radiation causes physical damage to cells and DNA. • Radiation can excite DNA and result in the destruction on the DNA backbone. • At high doses of radiation (10,000 - 15,000 rads), death occurs in a few hours

13. Radiation is used positively in a variety of ways 15 • Medicine • For example, radiation and radioactive tracers • are used to diagnose and treat medical problems. • Radiation therapyused to treat cancer

14. 17 Generate electrical power Nuclear fission is used to generate electricity Dating Used to tell the age of fossils or rocks

15. 18 Fission and Fusion Fission Fusion Splitting a nucleus Combining of two nuclei.

17. 19 • Nuclear power can come from the fission of uranium, plutonium or thorium or the fusion of hydrogen into helium. • Today it is almost all uranium.

18. 21 • FUSION • A fusion reaction occurs when nuclei of light elements, specifically hydrogen and its isotopes (deuterium, or "heavy water," and tritium), are forced together at extremely high temperatures and densities until they fuse into nuclei of heavier elements and release enormous amounts of energy.

19. 22 Half Life is the amount of time it takes for half of the nuclei in a sample to decay Mass (kg)

21. 14C • Radioactive 14C acts chemically just like 12C, so it becomes incorporated into plants an animals. • When the animal/plant dies the 14C begins to decay into 14N at a know rate, so we can determine how long ago the organism died. • This is called Carbon Dating.

22. The half life of 14C is 5,730 years. If a sample originally contained 100 g, how much would be left after 11,460 years? 26 50g 25g

24. 3/14/13 • What is the most penetrating radioactive particle?

25. Answer • Gamma Rays