WEBVTT - How Do Isotopes Work?

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<v Speaker 1>Welcome to brain Stuff production of I Heart Radio. Hey,

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<v Speaker 1>brain Stuff, Laurin bobble bomb. Here. Atoms are the building

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<v Speaker 1>blocks of matter. Anything that has mass and occupies space

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<v Speaker 1>by having volume is made up of these we things

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<v Speaker 1>that goes for the air you breathe, the water you drink,

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<v Speaker 1>and your body itself. Isotopes are a vital concept in

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<v Speaker 1>the study of atoms and how they work. Chemists, physicists,

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<v Speaker 1>and geologists use them to make sense of our world.

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<v Speaker 1>But before we can explain what isotopes are or why

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<v Speaker 1>they're so important, we'll need to take a step back

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<v Speaker 1>and look at atoms as a whole. As you probably know,

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<v Speaker 1>atoms have three main components, two of which reside in

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<v Speaker 1>the atoms nucleus, located at the center of the atom.

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<v Speaker 1>The nucleus is a tightly packed cluster of particles. Some

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<v Speaker 1>of those particles are protons, which have positive electrical charges.

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<v Speaker 1>It's well documented that opposite charges attract, while similarly charged

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<v Speaker 1>bodies tend to repel one another. I think about the

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<v Speaker 1>ends of two magnets. So here's a question. How can

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<v Speaker 1>two or more protons with their positive charges come exist

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<v Speaker 1>in the same nucleus? Shouldn't they be pushing each other away.

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<v Speaker 1>That's where another type of particle comes in, neutrons. Neutrons

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<v Speaker 1>are subatomic particles that share nuclei with protons, but neutrons

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<v Speaker 1>don't possess an electrical charge. True to their name, neutrons

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<v Speaker 1>are neutral, being neither positively nor negatively charged. It's an

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<v Speaker 1>important attribute. By virtue of their neutrality, neutrons can stop

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<v Speaker 1>protons from driving one another clear out of the nucleus.

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<v Speaker 1>Orbiting the nucleus are the third main component of atoms, electrons,

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<v Speaker 1>which are ultra light particles with negative charges. Electrons facilitate

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<v Speaker 1>chemical bonding, and their movements can produce a little thing

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<v Speaker 1>called electricity. But protons are no less important for one thing,

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<v Speaker 1>they help scientists tell the elements apart. You might have

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<v Speaker 1>noticed that in most versions of the periodic table, each

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<v Speaker 1>square has a little number printed in its upper right

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<v Speaker 1>hand corner. That figure is known as the atomic number.

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<v Speaker 1>It tells the reader how many protons are in the

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<v Speaker 1>atomic nucleus of a given element. For example, Oxygen's atomic

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<v Speaker 1>number is eight. Every oxygen atom in the universe has

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<v Speaker 1>a nucleus with exactly eight protons, no more, no less.

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<v Speaker 1>Without this very specific arrangement of particles, oxygen wouldn't be oxygen.

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<v Speaker 1>Each elements atomic number, including oxygen's, is totally unique, and

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<v Speaker 1>it's a defining trait. No other element has eight protons

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<v Speaker 1>per nucleus. By counting the protons, you can identify an atom.

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<v Speaker 1>Just as oxygen atoms will always have eight protons, nitrogen

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<v Speaker 1>atoms invariably come with seven. It's that simple neutrons do

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<v Speaker 1>not follow suit the nucleus, and an oxygen atom is

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<v Speaker 1>guaranteed to harbor eight protons as we've established, However, it

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<v Speaker 1>might also contain anywhere from four to twenty neutrons. Isotopes

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<v Speaker 1>are variants of the same chemical element that have different

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<v Speaker 1>numbers of neutrons. Now, each isotope is named on the

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<v Speaker 1>basis its mass number, which is the total combined number

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<v Speaker 1>of neutrons and protons in an atom. For example, one

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<v Speaker 1>of the better known oxygen isotopes is called oxygen eighteen

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<v Speaker 1>because it's got the standard eight protons plus ten neutrons.

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<v Speaker 1>A related isotope, oxygen seventeen, has one fewer neutron in

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<v Speaker 1>the nucleus. Some combinations of subatomic particles are stronger than others.

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<v Speaker 1>Scientists classify oxygen seventeen and eighteen as stable isotopes. In

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<v Speaker 1>a stable isotope, the forces exerted by the protons and

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<v Speaker 1>neutrons hold each other together permanently, keeping the nucleus intact

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<v Speaker 1>on the flip side. The nuclei in radioactive isotopes, also

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<v Speaker 1>called radio isotopes, are unstable and will decay over time.

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<v Speaker 1>These things have a protons neutron ratio that's fundamentally unsustainable

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<v Speaker 1>in the long run. Nobody wants to stay in that predicament. Hence,

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<v Speaker 1>radioactive isotopes will shed some subatomic particles and release energy

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<v Speaker 1>while they're at it until they've converted themselves into nice

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<v Speaker 1>stable isotopes. So oxygen eighteen is stable, but oxygen nineteen

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<v Speaker 1>is not. The latter will inevitably break down and fast

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<v Speaker 1>within twenty six point eight eight seconds of its creation.

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<v Speaker 1>Any given sample of oxygen nineteen is guaranteed to lose

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<v Speaker 1>half of its atoms to the ravages of decay. That

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<v Speaker 1>means of oxygen nineteen has a half life of twenty

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<v Speaker 1>six point eight eight seconds. A half life is the

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<v Speaker 1>amount of time it takes of an isotope sample to decay.

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<v Speaker 1>Remember this concept, we're going to connect it to paleontology

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<v Speaker 1>in just a minute. But before we talk about fossil science,

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<v Speaker 1>there's an important point that needs to be made. Unlike oxygen,

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<v Speaker 1>some elements do not have any stable isotopes whatsoever. Consider

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<v Speaker 1>uranium in the natural world. There are three isotopes of

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<v Speaker 1>this heavy metal, and they're all radioactive. With the atomic

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<v Speaker 1>nuclei in a constant state of decay. Eventually a chunk

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<v Speaker 1>of uranium will turn into it altogether different element. Don't

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<v Speaker 1>bother trying to watch the transition in real time, though

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<v Speaker 1>the process unfolds very very slowly. Uranium two thirty eight,

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<v Speaker 1>the elements most common isotope, has a half life of

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<v Speaker 1>about four point five billion years. Gradually it will become

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<v Speaker 1>lead to OH six, which is stable. Likewise, uranium two

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<v Speaker 1>thirty five, with its seven hundred and four million year

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<v Speaker 1>half life, transitions into lead to OH seven, another stable isotope.

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<v Speaker 1>Two geologists, this is really useful information. Let's say somebody

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<v Speaker 1>finds a slab of rock whose zircon crystals contain a

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<v Speaker 1>mixture of uranium two thirty five and lead to OH seven.

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<v Speaker 1>The ratio of those two atoms can help scientists determine

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<v Speaker 1>the rocks age. Here's how Let's say the lead atoms

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<v Speaker 1>vastly outnumber their uranium counterparts. In that case, you know

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<v Speaker 1>you're looking at a pretty old rock. After all, the

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<v Speaker 1>uraniums had plenty of time to start transforming itself into lead.

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<v Speaker 1>On the other hand, if the opposite is true, and

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<v Speaker 1>the uranium atoms are more common, then the rock must

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<v Speaker 1>be on the younger side. The technique we've just described

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<v Speaker 1>is called radiometric dating. That's the act of using the

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<v Speaker 1>well documented decay rates of unstable isotopes to estimate the

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<v Speaker 1>age of rock samples and geologic formations. A Paleontologists have

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<v Speaker 1>harnessed the strategy to determine how much time has elapsed

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<v Speaker 1>since a particular fossil was deposited, though it's not always

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<v Speaker 1>possible to date the specimen directly. You don't need to

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<v Speaker 1>be a prehistory buff to appreciate isotopes. Medical practitioners use

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<v Speaker 1>some of the radioactive varieties to monitor blood flow, study

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<v Speaker 1>bone growth, and even fight cancer. Radio Isotopes have also

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<v Speaker 1>been used to give farmers insights into soil quality. So

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<v Speaker 1>there you have it. Something as seemingly abstract as the

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<v Speaker 1>variability of neutrons affects everything from cancer treatment to the

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<v Speaker 1>mysteries of deep time. Science is awesome. Today's episode was

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<v Speaker 1>written by Mark Mancini and produced by Tyler Clang. Brain

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<v Speaker 1>Stuff is a production of iHeart Radio's How Stuff Works.

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<v Speaker 1>For more on this and lots of other stable topics,

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<v Speaker 1>visit our home planet has Stuff Works dot com. And

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