November 3,2011. Objective: Determine half life of pennies. Agenda: Notes Fossils Lab : Radioactive Decay Review for test. WHAT IS RADIOACTIVE DATING?. Most elements exist in several forms. These are isotopes. Example: Carbon. Radioactive decay. Same atomic # = same # of protons.
Carbon -14 has a short half-life of 5700 years.
Uranium-238has an extremely long half-life of 4.5 billion years.
Potassium-40has a half-life of 1.25 million years.