1. (7th) Chapter 8-3 Cornell Notes
Radioactive
Dating

2. Chapter 8-3 Key Questions
1. What happens during radioactive decay?
2. What can be learned from radioactive dating?

3. Chapter Key Terms
atom-
element-
radioactive decay-
half-life-

4. Chapter 8-3 Paragraph 1 rocks are matter;
atoms: tiny particles that make up matter;
element: when all particles the same type;
most elements stable but some unstable;
unstable elements = radioactive;
Radioactive decay: atoms of one unstable element break down into atoms of another element.

5. Chapter 8-3 Paragraph 2 radioactive elements found in igneous rock;
slowly decays over time;
changes into another element at steady rate;
rate of decay = “half-life” or the time it takes for ½ of the radioactive element to decay.

6. radioactive dating: used to determine absolute age;
potassium-40 commonly used;
potassium -40 decays into argon-40;
half-life = 1.3 billion years;
useful for very old rocks.
Chapter 8-3 Paragraph 3

7. Chapter 8-3 Paragraph 4 all plants/animals contain carbon;
carbon-14 useful dating radioactive element;
half-life of 5,370 years, can only date back to ~50,000 years.; .

8. difficult to date Earth, most early rocks destroyed/changed;
oldest rocks to date = 4.0 billion years;
moon rocks + meteorites used to date Earth;
radioactive dating moon = 4.6 billion years;
Earth inferred to be slightly older;
oldest living things = 3.5 billion years.
Chapter Paragraph 5