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# Radioisotopes - PowerPoint PPT Presentation

Radioisotopes. Radioisotopes. The decay of unstable isotopes is spontaneous, and takes place all the time. This was first observed by Henri Becquerel when he stored uranium ore in a drawer with photo film. Half Life. The half-life of a radioactive isotope is

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Presentation Transcript

• The decay of unstable isotopes is
• spontaneous, and takes place all the

time.

• This was first observed by Henri

Becquerel when he stored uranium ore

in a drawer with photo film.

Half Life
• The half-life of a radioactive isotope is

the time it takes for one half of a

sample of that isotope to decay.

The more slowly an isotope decays the

more slowly the alpha, beta, or gamma

Sample Problems
• Gold-191 has a half life of 12.4 hours.
• What mass of this isotope would remain

after 49.6 hours if you started with

7.5mg

• 0.469 mg
Sample 2
• A sample of iodine-126 with an original mass of 15.000 mg loses 13.125 mg of the original mass in 39 days. What is the half life?
• 15.000mg – 13.125mg = 1.875mg

15.000/2 = 7.5 That’s 3 Half Lives

7.5/2 = 3.75 39 days / 3 = 13 days

3.75/2 = 1.875