Radioactive Dating pp 282-284

Earth Estimated age to be around 4.6 billion years Took about 1.5 billion years for swirling gases to form the planet How do we know this? Radioactive Dating

Radioactive decay Atomic nuclei release ½ of its radioactive energy every so many years (based on element) and leaves behind a different isotope That energy can be released as a neutron, proton, or electron EX. C14 (unstable) changes to C12 (stable)

Half-Life how long it takes to reduce the sample size by ½ Can measure the amount of the “new” isotope to determine age Isotope used must be appropriate to time window

3 x 1.3 billion years = 3.9 billion years The half life for Potassium-40 is about 1.3 billion years. If you are left with 1/8 of the sample, how much time has passed? 1 2 3 half lives 1  1/2  1/4  1/8 3 x 1.3 billion years = 3.9 billion years