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Absolute Ages of Rocks Sci. 3.3 Absolute age: • Age in years Question 1 Nucleus (center) of atom: • Protons, + charge • Neutrons, No charge (Neutral) • Electrons, - charge outside nucleus eP H eN P P e- N He Draw these e- e- PN NPN P e- Li Question 2 2a. Which subatomic particle is not found in the nucleus? P. n. e 2b. A neutron has a _____ charge. Positive, negative, no charge eP eN P P e- N H He 1P 2P e- PN NPN P e- Number of protons: • Determines identity of element e- Li 3P Question 3 3a. If a He atom lost a proton, it would become what element? H, Li, C, O 3b. If a He atom gained a proton, it would become what kind of atom? H, Li, C, O Number of neutrons: • Determines which form (isotope) of element Carbon 12 Carbon 14 6P 6N 6P 8N 12C 14C Nitrogen 14 7P 7N 14N Potassium 40 Sodium 23 19 P 21 N 11 P 12 N 40K 23Na Argon 40 18 P 22 N 40Ar Hydrogen 2 Nitrogen 15 1P 1N 7P 8N 2H 15N Phosphorus 28 15 P 13 N 28P Question 4 4a. How many neutrons does the isotope 14C have? 6, 7, 8, 14 4b. How many neutrons does the isotope 13C have? 6, 7, 8, 13 Some isotopes are unstable • Radioactive decay Parent material 14C Daughter material 14N e- Question 5 5a. All carbon atoms have __ protons. 6, 7, 8, 14 5b. All nitrogen atoms have __ protons. 6, 7, 8, 14 Half-life: • Time it takes for half of atoms to decay • Ex:14C = 5730 years (235U=700 m.y., 238U=4.5 b.y.) Question 6 6a. If an organism had 100g of 14C when it died around 11,500 years ago (2 half-lives), how much 14C would it have today? 200, 50, 25g, 15g 6b. If an organism had 120g of 14C when it died around 17,000 years ago (3 half-lives), how much 14C would it have today? 360, 60, 30g, 15g Radiometric dating: • Calculating age based on half-life • ratio of parent material to daughter material Question 7 Radiocarbon dating: • • • • For dating dead things good to 75k years ago For original remains only (dinos 65mil ) Shroud of Turin Question 8 8a. Would radiocarbon dating be useful for dating the exact age of the earth (~4.6 billion years)? Y/N 8b. Would radiocarbon dating be useful for dating a trace fossil that is around 50k years old? Y/N Earth’s age • ~4.5 bil. years • Oldest rocks ~3.9 bil Question 9 9a. The earth is approximately how old? 4.5 bil, 4.5 mil, 4.5 thousand 9b. When the earth first formed, its surface: was molten rock, lacked liquid water, did not have an atmosphere, all of the above uniformitarianism: • Processes that change the earth today, are the same that changed it in the past Question 10 10a. The processes that shape the earth’s surface generally work: very slowly, very quickly 10b. Which process forms new elements? uniformitarianism, superposition, permineralization, radioactive decay