Exercise 7 : Radioactive Decay

We have talked about the so-called 92 naturally occurring elements. Elements with atomic numbers 92 have been synthesized in reactors and during high energy physics experiments.

A close examination of elements with atomic numbers 1 to 92, however, reveals that several are no longer detectable on Earth.

1. Using your searching skills, find two of the "naturally occurring elements" that are no longer detectable on Earth.

2. Write a paragraph about radioactive decay. (You may wish to review the short animation) Include the concepts of parent, daughter and half-life. What percentage of the parent remains after 10 half-lives?

3. If the two "missing" elements you identified in (1) are no longer detectable, why do scientists believe that they were originaly present on Earth? _________________________________________________________________________________________________

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   Copyright by John C. Butler, July 29, 1995