1. RADIOACTIVE DECAY: understand radioactive decay. describe alpha, beta and gamma radiation?

2. Atomic Theory and Radioactive Decay  Natural background radiation exists all around us.  This radiation consists of high energy particles or waves being emitted from a variety of materials.  Radioactivity is the release of high-energy particles or waves.  Being exposed to radioactive materials can be beneficial or harmful. X rays, radiation therapy, and electricity generation are beneficial. High-energy particles and waves damage DNA in our cells.  When atoms lose high-energy particles and waves, ions or even new atoms can be formed.  High-energy waves and particles are called radiation when they leave the atom. The electromagnetic epectrum

3. Searching for Invisible Rays  Radiation is everywhere, but can be difficult to detect.  Roentgen named X rays with an “X” 100 years ago because they were previously unknown.  Becquerel realized uranium emitted seemingly invisible energy as well.  Marie Curie and her husband Pierre named this energy radioactivity. Early discoveries of radiation relied on photographic equipment.  Later, more sophisticated devices such as the Geiger- Müller counter were developed to more precisely measure radioactivity. Radium salts, after being placed on a photographic plate, leave behind the dark traces of radiation.

4. RADIOACTIVITY: Radioactivity: release of high-energy particles as a result of changes in the nuclei of atoms (nucleus of atom decays) Radiation: high energy rays and particles that are released by radioactive sources found on the electromagnetic spectrum (as seen below).

5. Nuclear Reaction:  When the number of neutrons or protons in a nucleus change or when radiation is released from the nucleus.

6. Radioactive Decay:  Results in formation of new atoms  Caused by unstable nucleus: nuclei lose energy and break apart.  Radioactive decay releases energy from nucleus as radiation  Radioactive atoms release energy until stable, often as different atoms.  Radioisotopes: Are natural or human-made isotopes that decay into other Isotopes, releasing radiation.

7. Focus Questions:  What is a radioisotope?  What is meant by radioactivity?  What conditions in the nucleus cause decay?  What is a stable isotope?

8. Three Types of Radiation:  Rutherford identified three types of radiation using an electric field. 1) Positive alpha particles were attracted to the negative plate. 2) Negative beta particles were attracted to the positive plate. 3) Neutral gamma rays did not move towards any plate.

9. 1) Alpha Decay  Release of alpha particles from nucleus = Alpha decay  Positively charged particles  Most massive of radiation types  Are slow moving particles; a sheet of paper will stop an alpha particle  Same particles found in the Helium atom  Alpha particle released, atomic # reduced by 2, mass by 4. Radium-226 releases an alpha particle and becomes Radon-222. Radon has two less protons than radium.

10. 2) Beta Decay  A beta particle is an electron that is negatively charged  Beta particles have a mass of 0, a charge of -1  Aluminum will stop beta particle  Beta decay occurs when a neutron changes into a proton + an electron.  Proton stays in nucleus, atomic number increases by one on the periodic table. Iodine-131 releases a beta particle and becomes xenon-131. A neutron has turned into a proton and the released electron. Atomic Mass does not change

11. 3) Gamma Decay:  Gamma radiation is a ray of high-energy, short-wavelength radiation.  Highest energy form of electromagnetic radiation.  Only lead and concrete can stop gamma rays.  No charge; no mass  Gamma decay results from energy being released from a high-energy nucleus  Gamma Ray-when the isotope changes from high-energy state to lower energy

12. Focus Questions:  What is an alpha particle?  What is beta decay?  What is gamma radiation?