November 3,2011

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# November 3,2011 - PowerPoint PPT Presentation

November 3,2011. Objective: Determine half life of pennies. Agenda: Notes Fossils Lab : Radioactive Decay Review for test. WHAT IS RADIOACTIVE DATING?. Most elements exist in several forms. These are isotopes. Example: Carbon. Radioactive decay. Same atomic # = same # of protons.

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Presentation Transcript

Objective:Determine half life of pennies

• Agenda:
• Notes
• Fossils
• Review for test

• Same atomic # = same # of protons.
• Different atomic mass = different # of neutrons.
• The nucleus contains protons and neutrons, which is most of the mass.
• Some atoms have an unstable nucleus.
• These elements can turn into other elements.
• This is called radioactive decay.
Half-life
• The half-life of an isotope is the amount of time it takes for exactly half of the atoms to decay. At the end of one half-life, half of the original atoms will have decayed.
• 1st half-life 1/2 of original left
• 2nd half-life 1/4 of original left
• 3rd half-life 1/8 of original left
• 4th half-life 1/16 of original left
• Half-lives can be used to estimate the age of rocks. We usually need to use isotopes with long half-lives because rocks can be billions of years old.

Carbon -14 has a short half-life of 5700 years.

Uranium-238has an extremely long half-life of 4.5 billion years.

Potassium-40has a half-life of 1.25 million years.

Westmoreland State Park

http://www.fossilguy.com/sites/potomac/

Fossil observations
• Draw 7 fossils
• Observation
• Inference