1. Absolute Dating It’s a decaying relationship.

2. Radioactivity Henri Becquerel discovered radioactivity in 1895. Until then there was no way of finding the absolute age of a rock or fossil.

3. Elements Elements are composed of atoms. Atoms are composed of 3 different kinds of particles: protons (+), neutrons (0) and electrons(-). Protons and neutrons are found in the nucleus, electrons in the space around the nucleus.

4. Isotopes An isotope of an element differs in the number of neutrons in the nucleus. Some isotopes are unstable and undergo radioactive decay. During the decay process they are transformed into more stable elements.

5. Half-life Each radioisotope has a predictable constant rate of decay. This means that over a given period of time a fraction of the atoms in a sample will disintegrate. The length of time needed for half of the sample to disintegrate is called the half-life.

6. The decay process is not changed by different temperatures or pressure. Half-lives of radioactive isotopes vary from a fraction of a second to billions of years. Ex. Iodine-131, half-life 8 days. The original element is called the parent isotope and the product of decay is called the daughter isotope.

9. Carbon-14 Important to scientists studying recent artifacts. Can be used only with organic remains. Has a half-life of 5,700 years. Only useful with artifacts up to 50,000 years old.

10. Isotope Half-life Polonium-2140.164 second Oxygen-152 minutes Bismuth-21260.5 minutes Sodium-2415 hours Iodine-1318 days Phosphorus-3214.3 days Cobalt-605.3 years Carbon-145,730 years Plutonium-23924,110 years Uranium-2384.5 billion years