Half-Life and Radiometric Dating

In Chapter 12, the concept of half-life was used in connection with the time it took for reactants to change into products during a chemical reaction. Radioactive decay follows first order kinetics (Chapter 12). First order kinetics means that the decay rate 

One possible decay series for radium. Ra-226 is trausformed into stable Pb-206 through a series of alpha and beta emissions. Horizontal arrows represent beta emissions and diagonal arrows alpha emissions. 

At any given time, a parent nucleus may decay into a daughter. Although it cannot be known when any individual nucleus may decay into a daughter, the half-life can be used as a collective measure of the time it 

The amount of a radioactive substance is cut in half after each consecntive half-life. The amount of the original material remaining after n half-lives is ( /)  

The half-life of isotopes provides scientists with a nuclear clock that can be used to date objects. The concept is based on knowing the fraction of original material that is present in a sample. For instance, if half of the original isotope is present in the sample, then the sample s age is equivalent to the isotope s half-life. If one-fourth of the original material is present, then the sample s age is 2 half-lives. Because the use of radio-metric dating involves making accurate measurements of parent and daughter activities in the sample, it is assumed that parent 

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