It's a Date! Exploring Radioactive Dating

Today we will be exploring radioactive dating.

Radioactive dating is a type of absolute dating - it can help us figure out when a rock formed. It is especially useful in igneous rocks.

Rocks are made up of minerals which are made of elements. Some of these elements are radioactive. If an element is radioactive, it lets off radiation, which is a type of energy, as it decays/breaks down.

Please take the following notes (only the italics) in your science notebook:

Radioactive Dating

A. Atomic structure of an element:
     Elements are made up of three types of particles:
     1. protons: these are found in the element's nucleus and have a positive (+) charge
     2. neutrons: these are found in the element's nucleus and have no charge
     3. electrons: these are found in the element's electron cloud and have a negative (-) charge

B. Many elements have isotopes

    1. Isotopes have the same number of protons, but a different number of neutrons

    2. Sometimes even if an element is not radioactive, it's isotopes may be radioactive

    3. Carbon (C) has a radioactive isotope, C-14, that decays to C-12 which is stable. Carbon is found

     only in living or once living things

C. The nuclei of radioactive elements and isotopes decay...

    1. ....to stable daughter products (Uranium (U) to lead (Pb))

    2. ....at a defined rate called a half-life

        a. half-life (t1/2): the amount of time it takes for half the nuclei of a radioactive sample to break

       down/decay to a stable daughter product

       b. t1/2 of Uranium-235: 703.8 million years (my)

       c. t1/2 of Carbon-14: 5,730 years

1) When you finish copying the notes, write your name and your partner's name on a sheet of notebook paper.
2) Ask me for a problem and work on it. Write the problem number and answer on your answer sheet.
3) When you finish, ask me to check your answer.
4) Get a new card.
5) At the end of the period, turn in your sheet. You do not need to do every problem. You do need to work efficiently for the entire period or you will lose points.

If you finish early, work on your project or Geologic Time Scale Walk questions.

Thanks!
Ms. Nickel