Carbon dating tutorial

Carbon 14 dating 1. Carbon 14 dating 2. Atomic number, atomic mass, and isotopes.

Radiometric dating

Video transcript What I want to do in this video is kind of introduce you to the idea of, one, how carbon comes about, and how it gets into all living things. And then either later in this video or in future videos we'll talk about how it's actually used to date things, how we use it actually figure out that that bone is 12, years old, or that person died 18, years ago, whatever it might be.

So let me draw the Earth. So let me just draw the surface of the Earth like that. It's just a little section of the surface of the Earth. And then we have the atmosphere of the Earth. I'll draw that in yellow. So then you have the Earth's atmosphere right over here. Let me write that down, atmosphere. And I'll write nitrogen.

Radiocarbon Calibration

Its symbol is just N. And it has seven protons, and it also has seven neutrons. So it has an atomic mass of roughly Then this is the most typical isotope of nitrogen. And we talk about the word isotope in the chemistry playlist. An isotope, the protons define what element it is. But this number up here can change depending on the number of neutrons you have.


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So the different versions of a given element, those are each called isotopes. I just view in my head as versions of an element.

So anyway, we have our atmosphere, and then coming from our sun, we have what's commonly called cosmic rays, but they're actually not rays. You can view them as just single protons, which is the same thing as a hydrogen nucleus. They can also be alpha particles, which is the same thing as a helium nucleus. And there's even a few electrons. And they're going to come in, and they're going to bump into things in our atmosphere, and they're actually going to form neutrons. So they're actually going to form neutrons.

And we'll show a neutron with a lowercase n, and a 1 for its mass number. And we don't write anything, because it has no protons down here. Like we had for nitrogen, we had seven protons.

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Carbon 14 dating 1 (video) | Khan Academy

So it's not really an element. It is a subatomic particle. But you have these neutrons form. And every now and then-- and let's just be clear-- this isn't like a typical reaction. But every now and then one of those neutrons will bump into one of the nitrogen's in just the right way so that it bumps off one of the protons in the nitrogen and essentially replaces that proton with itself.

So let me make it clear. For example, the radioactive isotope potassium decays to argon with a half life of 1. Other isotopes commonly used for dating include uranium half-life of 4. Problem 1- Calculate the amount of 14 C remaining in a sample. Problem 2- Calculate the age of a fossil.

How Carbon-14 is Incorporated Into Living Things

Problem 3- Calculate the initial amount of 14 C in a fossil. Problem 4 - Calculate the age of a fossil. Problem 5- Calculate the amount of 14 C remaining after a given time has passed. Decay of radioactive isotopes Radioactive isotopes, such as 14 C, decay exponentially. Modeling the decay of 14 C. Thus, we can write: Radiocarbon dating compares the present ratio of carbon to carbon to determine how long ago the living thing died.

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Carbon 14 C is produced in the atmosphere by the interaction of neutrons 1 n produced by cosmic rays with the stable isotope of nitrogen, nitrogen 14 N:. The carbon atoms produced are then incorporated into carbon dioxide CO 2 molecules to produce 14 CO 2 molecules which mix with the most common 12 CO 2 molecules in the atmosphere. The 14 CO 2 enters plant tissue as a result of photosynthesis or absorption through the roots.

The amount of 14 C produced in the atmosphere is balanced by the continual nuclear decay radioactive decay of 14 C to produce 14 N and a beta-particle:. Play the game now! When a plant or animal dies it stops taking in carbon and radioactive decay begins to decrease the amount of carbon in the tissues. The age of the plant or animal specimen containing carbon, such as wood, bones, plant remains, is determined by measuring the ratio of carbon to carbon The half-life of carbon is only years.

Because of this relatively short half-life, carbon can only be used to date specimens up to about 45, years old. After this the amount of carbon present in the sample is too small to be measured precisely. Carbon can not be used to measure the age of very young specimens as the difference between the amount of carbon and carbon will not be sufficient to be detected.