How is carbon dating done?
In this section we will explore the use of carbon dating to determine the age of fossil While 12C is the most abundant carbon isotope, there is a close to constant decay to calculate the amount of carbon at any given time using the equation. Dating a Fossil - Carbon dating compares the ratio of carbon to carbon atoms in an A formula to calculate how old a sample is by carbon dating is: . Radiocarbon dating is a method for determining the age of an object containing organic . In nature, carbon exists as two stable, nonradioactive isotopes: carbon (12 .. C remaining in the sample), the carbon-dating equation allows the.
How is carbon dating done?
BioMath: Carbon Dating
William Baker Answer Carbon 14 C14 is an isotope of carbon with 8 neutrons instead of the more common 6 neutrons. It is unstable, and scientists know that it radioactively decays by electron emission to Nitrogen 14, with a half life of 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 years, half of it will still be carbon 14, and the other half will have decayed.
Or in other words, if we have a box, and we don't know how old it is but we know it started with carbon 14 atoms, and we open it and find only 50 carbon 14 atoms and some other stuff, we could say, 'Aha! It must be 1 carbon 14 half-life or years old. 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?
That's actually kind of cool.
It's a semi-long story, so bear with me. In the atmosphere, cosmic rays smash into normal carbon 12 atoms in atmospheric carbon dioxideand create carbon 14 isotopes. 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.
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.
How is carbon dating done?
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.
- Radiocarbon dating
- How Carbon-14 Dating Works
- Carbon 14 dating 1
Like we had for nitrogen, we had seven protons. 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.
Carbon 14 Dating Calculator
So let me make it clear. So it bumps off one of the protons. So instead of seven protons we now have six protons.
But this number 14 doesn't go down to 13 because it replaces it with itself. So this still stays at And now since it only has six protons, this is no longer nitrogen, by definition.
This is now carbon. And that proton that was bumped off just kind of gets emitted. So then let me just do that in another color.
And a proton that's just flying around, you could call that hydrogen 1. And it can gain an electron some ways. If it doesn't gain an electron, it's just a hydrogen ion, a positive ion, either way, or a hydrogen nucleus. But this process-- and once again, it's not a typical process, but it happens every now and then-- this is how carbon forms.
So this right here is carbon You can essentially view it as a nitrogen where one of the protons is replaced with a neutron. And what's interesting about this is this is constantly being formed in our atmosphere, not in huge quantities, but in reasonable quantities. So let me write this down. And let me be very clear. Let's look at the periodic table over here. So carbon by definition has six protons, but the typical isotope, the most common isotope of carbon is carbon So carbon is the most common.
So most of the carbon in your body is carbon But what's interesting is that a small fraction of carbon forms, and then this carbon can then also combine with oxygen to form carbon dioxide.
And then that carbon dioxide gets absorbed into the rest of the atmosphere, into our oceans. It can be fixed by plants. When people talk about carbon fixation, they're really talking about using mainly light energy from the sun to take gaseous carbon and turn it into actual kind of organic tissue. And so this carbon, it's constantly being formed.
It makes its way into oceans-- it's already in the air, but it completely mixes through the whole atmosphere-- and the air. And then it makes its way into plants.Radiocarbon Dating
And plants are really just made out of that fixed carbon, that carbon that was taken in gaseous form and put into, I guess you could say, into kind of a solid form, put it into a living form. That's what wood pretty much is. It gets put into plants, and then it gets put into the things that eat the plants. So that could be us.
Now why is this even interesting? I've just explained a mechanism where some of our body, even though carbon is the most common isotope, some of our body, while we're living, gets made up of this carbon thing.
Well, the interesting thing is the only time you can take in this carbon is while you're alive, while you're eating new things. Because as soon as you die and you get buried under the ground, there's no way for the carbon to become part of your tissue anymore because you're not eating anything with new carbon And what's interesting here is once you die, you're not going to get any new carbon And that carbon that you did have at you're death is going to decay via beta decay-- and we learned about this-- back into nitrogen So kind of this process reverses.