Unit 3: The Atom Part 4

1
Unit 3 The Atom Part 4

• Radiation and Nuclear Chemistry

2
Radioactivity

• There are two main types of radioactivity
• Natural radon in the soil
• Induced made by people in power plants or
  research labs

3
Natural Radioactivity

• Occurs in nature
• Usually large, unstable nuclei
• Occurs in three ways
• ? Particle (alpha particle)
• ? Particle (beta particle)
• ? Ray or wave (gamma ray)

4
Alpha Decay ?

• A helium nucleus is released from the nucleus
  
• The mass decreases by 4
• The atomic number decreases by 2
• (Because the He nucleus has 2p and 2no)
• Alpha radiation can be stopped by a piece of
  paper. Cannot penetrate skin. Not dangerous.

5
Alpha Decay Example
Notice that the uranium has decomposed into a new
element, thorium (Th)
6
Beta Decay ?

• An electron is released from the nucleus as a
  neutron decomposes into a proton.
• The mass is unaffected. (the mass of a neutron is
  roughly equal to the mass of a proton)
• The atomic number is increased by 1.
• Harder to stop and more dangerous.

7
Beta Decay Example
Notice that carbon has changed into nitrogen.
8
Gamma Decay ?

• Pure electromagnetic energy is released from the
  nucleus.
• The mass and atomic number are unaffected.
• Stopped by lead. The most harmful radiation type
  to living tissue.

9
Gamma Decay Example
No new element formed. Gamma radiation (energy)
released.
10
Induced Radioactivity

• Particles are slammed together to cause
  transmutation of stable elements. (Nuclear
  Bombardment)
• Discovered by Rutherford in 1919.

11
Uranium-238 Decay Series
12
Radioactive Decay of U-238

• Uranium-238 becomes Thorium-234
• Transmutation by Alpha Decay

13
Radioactive Decay of U-238
Thorium-234 becomes Protactinium-234 Transmutation
by Beta Decay
14
Radioactive Decay of U-238
Protactinium-234 becomes Uranium-234 Transmutation
by Beta Decay
15
Radioactive Decay of U-238
Uranium-234 becomes Thorium-230 Transmutation by
Alpha Decay
16
Radioactive Decay of U-238
Thorium-230 becomes Radium-226 Transmutation by
Alpha Decay
17
Radioactive Decay of U-238
Radium 226 becomes Radon-222 Transmutation by
Alpha Decay
18
Radioactive Decay of U-238
Radon-222 becomes Polonium-218 Transmutation by
Alpha Decay
19
Radioactive Decay of U-238
Polonium-218 becomes Lead-214 Transmutation by
Alpha Decay
20
Radioactive Decay of U-238
Lead-214 becomes Bismuth-214 Transmutation by
Beta Decay
21
Radioactive Decay of U-238
Bismuth-214 becomes Polonium-214 Transmutation by
Beta Decay
22
Radioactive Decay of U-238
Polonium-214 becomes Lead-210 Transmutation by
Alpha Decay
23
Radioactive Decay of U-238
Lead-210 becomes Bismuth-210 Transmutation by
Beta Decay
24
Radioactive Decay of U-238
Bismuth-210 becomes Polonium-210 Transmutation by
Beta Decay
25
Radioactive Decay of U-238
Polonium-210 becomes Lead-206 Transmutation by
Alpha Decay Lead-206 is stable. (phew!)