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Aim : How can the decay of an organism tell us its age?

Aim : How can the decay of an organism tell us its age?. Do Now : Think about this… If you were standing 10 feet from the wall, and I asked you to walk half the distance to the wall, how close would you be? If I asked you to repeat this process, would you ever reach the wall?.

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Aim : How can the decay of an organism tell us its age?

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  1. Aim: How can the decay of an organism tell us its age? Do Now: Think about this… If you were standing 10 feet from the wall, and I asked you to walk half the distance to the wall, how close would you be? If I asked you to repeat this process, would you ever reach the wall?

  2. Basic Atomic Structure DO NOT COPY • Electrons – Orbit the nucleus (negative electrical charges). • Atomic number is the number of protons in the atom’s nucleus.  Mass number is the number of protons plus neutrons in an atom’s nucleus.

  3. I. Isotopes - the unstable form of an element. - The atoms have the same number of protons and different number of neutrons.

  4. DO NOT COPY EXAMPLE Stable Element, Carbon-12: -6 Protons -6 Neutrons Unstable Element (Isotope), Carbon-14: -6 Protons -8 Neutrons

  5. II. Radioactivityrefers to energy and particles emitted from unstable isotopes. This is known as radioactive decay (Isotope)

  6. III. Absolute Age : (Radioactive dating) - Using precise numbers to tell when an organism lived or an event occurred. - This can be done by using radioactive isotopes. cover of your ESRT.

  7. IV. Radioactive Decay • Continues at a regular rate (not affected by outside factors). • The first isotope is called the parent nuclei. (unstable) • When it decays, it turns into the daughter nuclei. (stable isotope)

  8. A. Half – Life: - time required for half of the atoms in a sample of radioactive element to decay. **The parent nuclei (Red) changes to the daughter nuclei (Blue)

  9. V. Dating with Carbon-14 • Used to date most recent organic material. (organisms and plants) • Shortest half-life. • Found in people

  10. Examples: Use your ESRT How many years will it take for two half-lives to pass of C14? What % of C14 will remain at this point? Which isotope has the longest half life? What is it? 11,400 yrs 25% C14 will remain Rubidium-87 (87Rb)

  11. Example 1: Use your ESRT If you can see in a rock sample there is 1/4 C14 and 3/4 N14, the sample must have gone through how many half-lives? Two half-lives. How old is this sample? 11,400 yrs old.

  12. EXAMPLE A student found a fossil and by looking at the radioactive decay of C14 she found there to be 1/16th of C14 remaining in the fossil. How many half lives has this sample gone through? The sample has gone through 4 half-lives

  13. Half-Life % Parent Remaining Number of years 0 1/1 0 1 1/2 5,700 2 1/4 11,400 3 1/8 17,100 4 1/16 22,800

  14. Closure: Obtain the worksheet form the back, we are going to work on it together.

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