1. 20-4 Radioactive Elements

2. Nuclear Reaction  Involve the particles in the nucleus of atoms  Can change one element into a new element if the number of protons are changed

3. Isotopes  Atoms with the same number of protons, but different number of neutrons  12 C has 6 protons and 6 neutrons  14 C has 6 protons and 8 neutrons

4. Radioactive Decay  Nuclei of unstable isotopes release fast- moving particles and energy. 3 types: 1. Alpha Decay – 2 protons & 2 neutrons are released 2. Beta Decay – 1 proton is added & 1 neutron is subtracted 3. Gamma Decay – doesn’t change number of protons or neutrons, but gives off gamma rays

5. Alpha Decay Beta Decay ***

6. Half-Life  Length of time needed for ½ of the atoms of a sample to decay  ½ life is different for each isotope  ½ life is useful in determining the ages of rocks and fossils = radioactive dating

8. Problems & Uses  Radioactivity, especially gamma radiation, can damage the cells of living organisms  Nuclear reactions release enormous amounts of energy, & are used in nuclear power plants  Radiation therapy uses radioactive elements to destroy cancer cells  Radioactive isotopes are used as tracers and to diagnose disease  Problem of disposing radioactive waste

9. In a nuclear reaction what can change? 1. Number of protons 2. Number of electrons 3. Number of neutrons 4. Both #1 & 3 1234567891011121314151617181920 2122232425262728293031323334353637383940 0

10. What is an isotope? 1. An atom with a different # of protons 2. An atom with a different # of electrons 3. An atom with a different # of neutrons 4. None of the above 1234567891011121314151617181920 2122232425262728293031323334353637383940 0 of 40

11. Alpha, beta, & gamma decay all produce a new element. 1. True 2. False 1234567891011121314151617181920 2122232425262728293031323334353637383940 0 of 40

12. ½ life of a radioactive element can vary with the conditions under which it occurs. 1. True 2. False 1234567891011121314151617181920 2122232425262728293031323334353637383940 0 of 40

13. Which of the following is not a use of radioactive isotopes? 1. Radiation therapy 2. To produce electricity 3. To make salt 4. As tracers 1234567891011121314151617181920 2122232425262728293031323334353637383940 0 of 40

14. Which type of radiation is most harmful to living things? 1. Alpha decay 2. Beta decay 3. Gamma decay 1234567891011121314151617181920 2122232425262728293031323334353637383940 0 of 40