Those are just one part of the story, however. This piece will give a general overview of isotopes and how we use them to get meaningful data! To start off — an element on the periodic table contains protons, neutrons, and electrons, and is defined by the number of protons it has.
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An isotope of an element has the same number of protons, but can vary in its number of neutrons. For example, the element oxygen has 8 protons, but can have 8, 9, or 10 neutrons; therefore, oxygen has 3 isotopes. When we describe oxygen isotopes, we refer to them as oxygen 16, 17, and 18 8 protons plus however many neutrons. Now that we know how an isotope is defined, how do we use them?
It depends on what information we want. Isotopes can be broken into two primary categories: Stable isotopes are just as they sound - very stable!
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They do not undergo any type of decay to other elements. Radiogenic isotopes DO undergo decay, and this is where you may have heard of terms like half-lives and radioactivity. Now back to the original question — what the heck do we use these for? 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.
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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.
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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.
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. When rocks, including fossils, are created, potassium 40 K becomes trapped inside and slowly decays into argon 40 Ar.
Because the half-life of 40 K is 1. Unfortunately, radiocarbon dating and related techniques are not perfect.
For example, archaeologists must take the marine reservoir effect into account. However, oceans are so deep that the 14 C from the atmosphere takes a very long time to reach the bottom. Any location in the ocean that is deeper than 10 metres has 14 C levels that can be up to years older than on the surface.
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This means is that when humans and animals whose diets are rich in seafood will have 14 C levels that provide older radiocarbon dates. Archaeologists take the marine reservoir effect into account by making small corrections to test results. When his skeleton was discovered in , radiocarbon dating suggested it had been buried sometime between and However, other tests showed that the skeleton contained high levels of marine protein. After taking the marine reservoir effect into account, radiocarbon dating actually pointed to a burial date between and These corrected results supported the theory that the skeleton belonged to Richard III.
Since it was first used at the end of the s, radiocarbon dating has remained one of the most important tools used by archaeologists.
Although it is only one of many different dating methods, it is commonly used to determine the age of artifacts because most archaeological sites contain organic materials. Radiocarbon dating can help understand technological advances, determine when a group of people moved to a certain region, or even identify a famous king. From revolution to convention: Registration of subscription required to view full text. Teaching radioisotope dating using the geology of the Hawaiian islands Timothy J.