The Carbon Cycle Madison County Schools：碳循环麦迪逊县的学校

1、all living things contain carbon, some of it is carbon-14 carbon-14 is radioactive (unstable)it decays into nitrogen by beta decayc-14 half-life is 5730 years14014617cencosmic rays from space are always hitting the upper atmosphere of the earth, which is mostly nitrogenthe rays produce high energy n

2、eutrons which can blast into n-14 atoms (atomic # 7) the neutrons can knock out and replace a nitrogen proton:pc-14n-14nneutron hits nitrogen atom (7 protons + 7 neutrons) neutron sticks & proton gets knocked out, creating an atom of carbon-14 (6 protons and 8 neutrons)c-14 mixes with the rest o

3、f the carbon in the atmospherecosmic rays keep hitting more c-14 gets madec-14 (6p + 8n) is unstable and eventually beta decays back into n-14 (7p + 7n)pc-14n-14n plants take in co2 from the atmosphere - including a little bit of c-14 thats mixed in plants build the carbon into starch (food) - inclu

4、ding that bit of c-14 - you know whats next:plants herbivores carnivores almost all living things ultimately get their carbon from the air! continuous cycle ensures that all living organisms have a steady ratio of c-14 to c-12 in their bodies same ratio as in the air until they die! stop living, and

5、 c-14 is no longer replenished beta decay continually decreases c-14 no new c-14 coming in & c-12 is stablethe cycle if we compare c-14:c-12 ratio in a fossil with ratio in a living sample estimate how many half-lives passed. carbon dating the half life of c-14 is: 5730 years after about 9 half

6、lives c-14 gets extremely difficult to detect, even with high tech. equipment thats 51,570 years old so, c-14 is limited to dating formerly living artifacts that are less than 50,000 years old. half-life graph of carbon-14 bones of dead lizard have 1/16th amount of carbon-14 that living reptiles do now. how old is “lizzie”?answer: 1/16 = ()x = x x x = ()44 half- lives have passed since she died so bones are 5730yrs x 4 = 22,920 years old! scientists can choose radioactive elements that have longer half lives than c-14 age of some rocks can be det