1. Radioactive Elements

2. Radioactivity: An Imbalance of Forces in the Nucleus

3. Radioactivity: An Imbalance of Forces in the Nucleus
Strength of Force depends on distance !

4. Radioactivity: An Imbalance of Forces in the Nucleus
Strength of force depends on distance
SO.. Larger nuclei are less stable
Strong force less effective in holding nucleus together
Electrical (repulsive) forces have greater impact
Elements DECAY (come apart) over time

5. Radioactivity: Definition
Radioactivity: the process by which certain elements emit particular forms of radiation.
Radioactive: any element that emits any of these forms of radiation.

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.
1620 years
3240 years
6480 years
Start

8. Application: Carbon Dating

9. Reaction in a Nuclear Reactor

11. Radioactive Elements
Part 2
Jan 9, 2014

12. Different Ways to Decay – Types of Radioactive Particles
Alpha Particles (α)– 2 protons and 2 neutrons
Beta Particles (β)– split 1 neutron into proton and 1 electron
Gamma Particles (ɣ) – emits a photon

13. Half-life: Exponential Decay

14. Decay of 238U: Natural Decay Chain

15. Decay of 238U: Natural Decay Chain
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.

16. 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

17. 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
+2 Charge.
Tends to pick up electrons & convert to Helium

18. Types of Radioactive Particles
Alpha Particles Emits: 2 p + 2 n Example: Uranium-238  Thorium Helium-4
Element
Atomic #
(# protons)
Mass #
(# p + # n)
# neutrons
Uranium 92
238
146
Thorium 90
234
144
Helium 2 4

19. 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
-1 Charge.
Proton joins nucleus
Electron (-1 charge) is emitted

20. Types of Radioactive Particles
Beta Particles Loses: 1 n Gains: 1 p Emits: 1 e-
Example: Thorium -234  Protactinium – electron
Element
Atomic #
(# protons)
Mass #
(# p + # n)
# neutrons
Thornium 90
234
144
Protactinium 91
143

21. 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

22. Types of Radiation: Energy (Resistance to being stopped)

23. Types of Radiation: Charges-1 +2
Neutral

24. Types of Radiation: Charges+2
Neutral -1