C-14 is another radioactive isotope that decays to C-12. Because of its short half-life, the number of C-14 isotopes in a sample is negligible after about 50,000 years, making it impossible to use for dating older samples. in Earth-Space Science from West Chester University of Pennsylvania.C-14 is used often in dating artifacts from humans. Fiore taught high school science for 7 years and offered several teacher workshops to regarding education techniques.U-235 decays to Pb-207 with a half-life of 704 million years.Due to its long half-life, U-235 is the best isotope for radioactive dating, particularly of older fossils and rocks. The half-life of C-14, however, is only 5,730 years.
A particular isotope of a particular element is called a nuclide. That is, at some point in time, an atom of such a nuclide will undergo radioactive decay and spontaneously transform into a different nuclide.
For all other nuclides, the proportion of the original nuclide to its decay products changes in a predictable way as the original nuclide decays over time.