1. Radioactive Elements Part 1 Jan 2, 2013

2. Radioactivity: An Imbalance of Forces in the Nucleus

4. Forces dependent on distance SO.. Larger nuclei are less stable Neucleons less effective in holding nucleus together Electrical (repulsive) forces have greater impact

5. Types of Radioactive Particles Alpha Particles – 2 protons and 2 neutrons Beta Particles – split 1 neutron into 1 proton and 1 electron Gamma Particles – emits a photon

6. Half Life: Measures Decay Rate Half life refers to amount of time it takes for ½ of the radio active sample to decay Half life for a particular isotope is always the same

7. Half Life Half life measures decay rate  Ex. Every1620 years ½ of a sample of radium-226 will have decayed. Start 1620 years 3240 years 6480 years

8. Radioactive Elements Part 2 Jan 4, 2013

9. Half-life: Exponential Decay

10. Decay of 238 U: Natural Decay Chain

11. decays, through alpha-emission, with a half-life of 4.5 billion years to thorium-234 which decays, through beta-emission, with a half-life of 24 days to protactinium-234 which decays, through beta-emission, with a half-life of 1.2 minutes to uranium-234 which decays, through alpha-emission, with a half-life of 240 thousand years to thorium-230 which decays, through alpha-emission, with a half-life of 77 thousand years to radium- 226 which decays, through alpha-emission, with a half-life of 1.6 thousand years to radon- 222 which decays, through alpha-emission, with a half-life of 3.8 days to polonium-218 which decays, through alpha-emission, with a half-life of 3.1 minutes to lead-214 which decays, through beta-emission, with a half-life of 27 minutes to bismuth-214 which decays, through beta-emission, with a half-life of 20 minutes to polonium-214 which decays, through alpha-emission, with a half-life of 160 microseconds to lead-210 which decays, through beta-emission, with a half-life of 22 years to bismuth-210 which decays, through beta-emission, with a half-life of 5 days to polonium-210 which decays, through alpha-emission, with a half-life of 140 days to lead-206, which is a stable nuclide.

12. Types of Radioactive Particles Alpha Particles – 2 protons and 2 neutrons Beta Particles – split 1 neutron into 1 proton and 1 electron Gamma Particles – emits a photon

13. Types of Radioactive Particles Alpha Particles – 2 protons and 2 neutrons Lowest Energy Still fast enough to do damage Easily stopped Relatively large size and mass Large enough to do damage Easily stopped +2 Charge. Tends to pick up electrons & convert to Helium

14. Types of Radioactive Particles Alpha Particles Emits: 2 p + 2 n Example: Uranium-238  Thorium-234 + Helium-4 ElementAtomic # (# protons) Mass # (# p + # n) # neutrons Uranium92238146 Thorium90234144 Helium242

15. Types of Radioactive Particles Beta Particles - 1 n  1 p + 1 e - (emits e - ) Higher Energy Harder to stop than α particle Becomes part of material when stopped

16. Types of Radioactive Particles Beta Particles Loses: 1 n Gains: 1 p Emits: 1 e - Example: Thorium -234  Protactinium – 234 + electron ElementAtomic # (# protons) Mass # (# p + # n) # neutrons Thornium90234144 Protactinium91234143

17. Types of Radioactive Particles Gamma Particles – emits a photon Highest Energy Can do significant damage Hard to stop No charge Doesn’t combine with other materials No mass Hard to stop