2. Radioactivity• The spontaneous decay of certain unstable atomic nuclei.
3. Half- life• The time required for one half of the atoms of a radioactive substance to decay
4. Radiometric dating• The procedure of calculating the absolute ages of rocks and minerals that contain radioactive isotopes.
5. Radiocarbon dating• Method for determining age by comparing the amount of carbon-14 to the amount of carbon-12 in a sample
6. Key Concept• When nuclei are unstable, they spontaneously break apart, or decay, in a process called radioactivity.
7. Key Concept• A half-life is the amount of time necessary for one half of the nuclei in a sample to decay to its stable isotope.
8. Key Concept• Each radioactive isotope has been decaying at a constant rate since the formation of the rocks in which it occurs
9. Key Concept• As the uranium decays, atoms of the daughter product are formed, and measurable amounts of lead eventually accumulate.
10. Key Concept• An accurate radiometric date can be obtained only if the mineral remained in a closed system during the entire period since its formation.
11. Key Concept• When an organism dies, the amount of carbon-14 gradually decreases as it decays. By comparing the ration of carbon- 14 to carbon- 12 in a sample, radio0carbon dates can be determined.