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

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

Chapter 8-3 Key Terms atom- element- radioactive decay- half-life-

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.

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.

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

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.; .

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 8-3 Paragraph 5