Absolute Dating

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Absolute Dating

• Chapter 3, Sec.3

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Process to find the approximate age of rocks or
fossils
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Atoms

• Smallest part of matter
• Made of protons, neutrons, electrons
• Center called the nucleus

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• Everything is made of atoms

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• Protons, neutrons in nucleus
• Electrons move around nucleus

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• Every element has a diff. of protons

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Isotopes

• Atoms of the same element with different of
  neutrons

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Radioactive Decay

• Most atoms are stable
• Some are unstable and breakdown or decay
  (radioactive)

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• High energy particles are given off
• Can damage cells, organs, etc..
• X-rays, gamma rays, electrons, protons, neutrons

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• Decay occurs at a constant rate called half-life

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Half-life

• The time it takes for one-half of a sample to
  decay

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Problem

• I start with 10 grams of a sample
• Its half-life is 20 years
• After 20 years, how much left?
• After 40 years, how much left

5 grams
2.5 grams
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Some unstable isotopes decay into stable isotopes
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3 radioactive dating methods

• Uranium-Lead Method
• Potassium-Argon Method
• Carbon-14 Method