Monday, May 9, 2011

Half-life


What is half-life?
·       The amount of time it takes for half of a substance to undergo some specified process
·       Radioactive elements have different isotopes that decay at different rates
o   Varies with the type of isotopes
o   Short half-life
§  Oxygen (71 seconds)
o   Long half-life
§  Thallium(1.4 × 10 10 years)
§  Carbon(5,730 years)
·       Calculated by dividing 0.693 by the decay constant
o   Decay constant - dividing the number of observed disintegrations per unit time by the number of radioactive nuclei in the sample
o   Usually given the symbol k or λ
·       Is a measure of how reactive it is
o   Terms of radioactive decay
o   Participation in specific reactions

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