P2.6 Radioactivity

Observing Nuclear Radiation
1. A key discovery
  1. Henri Becquerel found a key on the photo he had developed under uranium salts
  2. Radiation passed through the paper but not the key
2. Marie Curie
  1. Discovered radioactivity
  2. 3 types of it, alpha, beta and gamma
3. A radioactive puzzle
  1. An unstable nucleus becomes stable by emitting radiation
4. Background radiation
  1. air, ground, building materials
  2. space, x rays, etc
The discovery of the nucleus
1. Originally people believes the plum pudding model
2. The Rutherford cone scene
Nuclear Reactions
1. Alpha Emission
  1. 2 protons, 2 neutrons
  2. Its relative mass is 4 and its relative charge is +2
  3. Atomic number decreases by 2, mass number goes down by 4
2. Beta Emission
  1. A neutron changes to an electron and a proton
  2. an electron is a beta particle
  3. Relative mass is 0 and relative charge is -1
  4. Atomic number goes up by 1 but mass the same
3. Gamma emission - uncharged and no mass
Alpha, Beta and Gamma
1. Penetrating power
  1. Alpha, absorbed by paper, travels 5cm in air
  2. Beta, absorbed by 5mm aluminium or 2-3mm lead, travels 1m in air
  3. Gamma, absorbed by thick lead or 1m concrete, unlimited in air
2. Deflection by Magnetic and electric fields
  1. Alpha: magnetic - deflected opposite to beta. electric - attracted to negative plate
  2. Beta: magnetic - easily deflected. electric - attracted to positive plate
  3. Gamma not deflected
Half Life
1. The activity is the number of atoms that decay per second
2. The amount of time taken for the isotope to halve

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P2.6 Radioactivity

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	Created by mhancoc3 about 11 years ago