1. Chapter 7: Radiation

2. Remember from Chemistry: Mass numberMass number: the number of protons + number of neutrons Atomic numberAtomic number: the number of protons in an atom of an element. Isotopes:Isotopes: atoms of the same elements that have a different number of neutrons and therefore a different mass number

3. There are many isotopes of carbon. For example: carbon-12, carbon-13 and carbon-14 How many protons in each of these atoms of carbon? –6–6 How many neutrons in each of these atoms of carbon? Carbon-12 = ____ neutrons Carbon-13 = ____ neutrons Carbon-14 = ____ neutrons

4. Carbon-12 = 12 C 6 Carbon-13 = _____ Carbon-14 = _____ Mass number Atomic number

5. Isotopes of Hydrogen Hydrogen: 1 proton and 0 neutrons Deuterium: 1 proton and 1 neutron Tritium: 1 proton and 2 neutrons

6. Radioactive Decay: The nuclei of some isotopes are stable, whereas, others are not. In unstable nuclei, the nuclear force is not enough to overcome the repulsive electrical forces with in the nucleus. As a result the nuclei are radioactive. When an unstable nucleus emits radiation, it undergoes a radioactive decay

7. Types of radioactive decay Alpha Decay:Alpha Decay: Particle emitted: Helium nucleus Result: Atom with two fewer protons and neutrons U → Th + He U → Th +

8. Types of radioactive decay BetaBeta Particle emitted: Electron Result: # of neutrons decrease by one and the # of protons increase by one = new element C → N + e C → N + β

9. GammaGamma Particle emitted: No particle, but gives off excess energy Result: No change to type of nucleus, it just has less energy. Ba → Ba + Gamma radiation Ba → Ba + Types of radioactive decay

10. Assignment: Fill in the 7.1 worksheets p125 (all) and 126 (odd numbers)

11. Half Life: Half Life: The time required for half the nuclei of a sample of a radioactive isotope to decay. The half life is the same regardless of the starting amount of the isotope. Because the amount of all radioactive isotopes decrease by half in each half life, graphs that show the amounts of these isotopes at various times look similar. The only difference is the time scale for decrease.

12. Examples of half life:

13. Half Life Table for Solving Word Problems Time# of Half livesAmount of parent isotope ** optional ** Amount of daughter isotope 00 Original Amount 0 1 2 3 4

14. Practice Problems

15. Homework: Fill in the 7.2 worksheets p134 and 135