What percentage of a radioactive isotope remains after 4 half-lives?

Name the element in group 17, period 2. (periodic table)

Name a brittle metal , which is used to galvanize iron

Which of the following reasons best explains why a scientist would want to replicate gregor mendel's pea plant experiment? a. to discover new aspects of the natural world b. to test the predictions of current theories c. to explain recently observed phenomena d. to test the conclusions of prior investigations