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Radio-Active Dating. HALF LIFE. Recap of Atoms. Parts of an atoms Nucleus (middle of atom) PROTONS – positive charge NEUTRONS – no charge ELECTRONS (outside nucleus) Negative charge. Mass Number & Isotopes. Protons & Neutrons have a mass of 1 each
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Radio-Active Dating HALF LIFE
Recap of Atoms • Parts of an atoms • Nucleus (middle of atom) • PROTONS – positive charge • NEUTRONS – no charge • ELECTRONS (outside nucleus) • Negative charge
Mass Number & Isotopes • Protons & Neutrons have a mass of 1 each • Mass number = protons + neutrons • Some elements have atoms that have a different number of neutrons • ISOTOPES • This changes their mass
Radio-active Decay • Isotopes that have unstable nuceli undergo radio-active decay • Radioactive isotopes • This means they release particles or radiant energy or BOTH
Half-Life • TIME it takes for ½ the amount of a radioactive isotope to decay • Many half-lives are known and can be seconds to thousands of years
Carbon Isotopes • Our body has lots of carbon in it • Mostly Carbon-12 • Some Carbon-14 • Carbon-14 has a half-life of 5,715 years
Try it out • If our sample starts with 100 sample size of carbon-14 and it now has 25, how many half lives have gone by? How many years old is the sample? • 2 half lives • 11,430 years