Chapter 21
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Transcript of Chapter 21
Radioactivity
Radioactivity- the spontaneous emission of radiation by an unstable atomic nucleus
Discovered by Henri Becquerel and the Curies
Atomic mass
SymbolAtomic number
Cannot see, hear, smell, taste or touch it.
Geiger counter Film badges Scintillation counter
Alpha, α Beta, β
Gamma, γ Decay- the release of
radiation by radioactive isotopes
Alpha particles Helium nucleus, 2 protons and 2 neutrons 4
2 He 2+
α Are large in size, move slowly Easily stopped by paper or clothing When an alpha particle is emitted from
Uranium, it decays to Thorium
High energy electron
0-1 e
β -
Neutron from the nucleus changes into a proton and an electron and the electron is emitted
Are smaller than alpha particles and move faster
Can be stopped by sheets of metal, wood, bricks
γ High energy form of electromagnetic
radiation No mass or charge Can pass through most materials Can be stopped by lead or thick concrete Usually accompanied by other forms of
radiation Most harmful form of radiation
Fission- a nuclear reaction in which a nucleus is broken into two or more smaller nuclei, creates a more stable nucleus
Chain reaction- a self-propagating reaction in which uranium absorbs a neutron by bombardment, the nucleus becomes unstable and splits, emitting neutrons and energy
Critical mass- the minimum amount of material needed to sustain a nuclear reaction
Fusion- the process where small nuclei join to form larger nuclei, creates a more stable nucleus
Energy produced from the fusion of 1 kilogram of Hydrogen into Helium to the fission of 1 kilogram of Uranium is 20:1
Moderators- used to slow down the speed at which the neutrons collide, can be water, beryllium or graphite
Control rods- rods/ plates that are lowered into the fuel rod assembly to absorb some of the neutrons, controls the rate of reaction
Carbon dating Medical diagnosis and treatment Tracers Preserving food