1. Radioactive Decay & C- 14 Dating Evolution Unit Chapter 14 p.382

2. How Radioactive Dating Works: All living organisms accumulate C-14 while they are aliveAll living organisms accumulate C-14 while they are alive Once the organism dies, it stops accumulating carbon and the C-14 it has slowly decays into N- 14 (nitrogen-14)Once the organism dies, it stops accumulating carbon and the C-14 it has slowly decays into N- 14 (nitrogen-14) We can measure the amount of C-14 left or N- 14 made to date any fossilWe can measure the amount of C-14 left or N- 14 made to date any fossil

3. Half-Life All fossils contain isotopes (different # neutrons) of elements that accumulated in the organisms when they were alive due to the atmosphere they lived in.All fossils contain isotopes (different # neutrons) of elements that accumulated in the organisms when they were alive due to the atmosphere they lived in. Half-life (for an isotope) is the # of years it takes for 50% (half) of the original sample to decay.Half-life (for an isotope) is the # of years it takes for 50% (half) of the original sample to decay.

4. Lets try a problem: A fossil was found in 1900. It contained.0625 g of C-14. The living organism contained 2 grams. How many years before 1900 did the organism die?A fossil was found in 1900. It contained.0625 g of C-14. The living organism contained 2 grams. How many years before 1900 did the organism die? 1.Step One: Figure out how many half lives there have been. 2 1.5.25.125.0625 2.Step Two: Count arrows=shows 5 half lives! 3.Step Three: Multiply # half lives by the time it takes for one half life to occur! 5(5,730)=28,650 years