# How is radioactive dating done

*02-Nov-2019 12:26*

They not only enjoyed this activity, but they really gained a better understanding of it as well.

Asked by: William Baker Carbon 14 (C14) is an isotope of carbon with 8 neutrons instead of the more common 6 neutrons.

And if you play with the exponential decay equations, you can come up with the nice formula (1/2)=(current decay rate)/(initial decay rate), where n is the number of half lives that have passed.

Voila, now you can tell how old a sample of organic matter is.

Once students are in their groups, with supplies, and general directions are given, they are on their own for doing their runs.

Students will record the number of M&Ms that are still "radioactive" (M side up) in their data table after each run, and set aside the "stable" (M side down) M&Ms.

Once all groups finish, each group records their info on the class decay table (on the board) and we calculate the averages of the class. Isotope Concepts: Students should begin to see the pattern that each time they dump out their M&Ms, about half become stable.

Once this info is calculated, students create a graph comparing the class average of parent isotopes to the number of half-lives. Students will be able to explain what a half-life of a rock is. Students will have a more in-depth understanding of what radioactive decay is. Students will understand how scientists use half-lives to date the age of rocks. Students then should be able to see the connection of the M&Ms and radioactive elements in rocks, and how scientists can determine the age of rocks by looking at the amount of radioactive material in the rock.

Adapted from: For Special Ed and ELL kids, you could give them a template of the data table/graph.So in the real world, looking at a sample like say a bone dug up by an archaeologist, how do we know how much carbon 14 we started with? This process is constantly occurring, and has been for a very long time, so there is a fairly constant ratio of carbon 14 atoms to carbon 12 atoms in the atmosphere.Now living plants 'breathe' CO indiscriminately (they don't care about isotopes one way or the other), and so (while they are living) they have the same ratio of carbon 14 in them as the atmosphere.It is unstable, and scientists know that it radioactively decays by electron emission to Nitrogen 14, with a half life of 5730 years.

This means that given a statistically large sample of carbon 14, we know that if we sit it in a box, go away, and come back in 5730 years, half of it will still be carbon 14, and the other half will have decayed.They will only re shake the radioactive M&Ms each time. Once they are finished with their 8 runs, they will record their data on the class data table (which can be on the board).