Carbon-14

**Daniel Rodríguez/****IB Chem-1**
**  Carbon-14   ** It is a species of carbon that contains 6 protons and 8 neutrons. It is mainly used for archaeological dating of living beings. Since all living beings contain carbon, then if the half life of carbon-14 is known, it is possible to find out the real (at least approximate) age of a certain fossil. So what really happens is that each living being has a more or less definite ratio of Carbon-12 to Carbon-14. Then this is how the original amount of Carbon-14 is calculated, and then it is compared to the current amount and based on calculations involving the half life of an isotope (the amount it takes for a sample of a certain isotope to lose half of its mass). Since Carbon-12 is a very stable isotope, then the parameters for the ratio can be kept the same throughout all the calculations. It is important to remember that:  · The half life of Carbon-14 is approximately 5700 years (±40).  · The ratio of Carbon-14 to Carbon-12 is around 1 to 1.4x10-12 grams.  · It is only precise for the numbers that range between 1,000 and 1,000,000 years, because less than a 1000 not much would have decayed and more than 1,000,000, the sample of C-14 would be so insignificant that it would not be precise at all.  · The resulting mass in a radioactive decay can be calculated using the geometric series: mi · (0.5) (number of years/half life of the isotope) For example: Some years ago, there was a certain animal whose amount of carbon-12 is 1.4x1012 grams (and therefore, using the ration it is going to have 1 gram of Carbon-14 by the time it dies). This animal’s fossil was found last month and now it was reported that it only had 0.25 grams of C-14 left. How many years does this fossil have? mi · (0.5) (number of years/half life of the isotope)=0.25 g   1 · (0.5) (number of years/5700)=0.25 g    log0.5(0.5) (number of years/5700)= log0.5(0.25) number of years/5700= log0.5(0.25) number of years= log0.5(0.25) · 5700 number of years= 11,400 References:  · [|www.physlink.com]  · [|www.ndt-ed.org]  · [|www.chemistry.about.com]