Speaker 1: Welcome to brain Stuff production of I Heart Radio. Hey,
Speaker 1: brain Stuff, Laurin bobble bomb. Here. Atoms are the building
Speaker 1: blocks of matter. Anything that has mass and occupies space
Speaker 1: by having volume is made up of these we things
Speaker 1: that goes for the air you breathe, the water you drink,
Speaker 1: and your body itself. Isotopes are a vital concept in
Speaker 1: the study of atoms and how they work. Chemists, physicists,
Speaker 1: and geologists use them to make sense of our world.
Speaker 1: But before we can explain what isotopes are or why
Speaker 1: they're so important, we'll need to take a step back
Speaker 1: and look at atoms as a whole. As you probably know,
Speaker 1: atoms have three main components, two of which reside in
Speaker 1: the atoms nucleus, located at the center of the atom.
Speaker 1: The nucleus is a tightly packed cluster of particles. Some
Speaker 1: of those particles are protons, which have positive electrical charges.
Speaker 1: It's well documented that opposite charges attract, while similarly charged
Speaker 1: bodies tend to repel one another. I think about the
Speaker 1: ends of two magnets. So here's a question. How can
Speaker 1: two or more protons with their positive charges come exist
Speaker 1: in the same nucleus? Shouldn't they be pushing each other away.
Speaker 1: That's where another type of particle comes in, neutrons. Neutrons
Speaker 1: are subatomic particles that share nuclei with protons, but neutrons
Speaker 1: don't possess an electrical charge. True to their name, neutrons
Speaker 1: are neutral, being neither positively nor negatively charged. It's an
Speaker 1: important attribute. By virtue of their neutrality, neutrons can stop
Speaker 1: protons from driving one another clear out of the nucleus.
Speaker 1: Orbiting the nucleus are the third main component of atoms, electrons,
Speaker 1: which are ultra light particles with negative charges. Electrons facilitate
Speaker 1: chemical bonding, and their movements can produce a little thing
Speaker 1: called electricity. But protons are no less important for one thing,
Speaker 1: they help scientists tell the elements apart. You might have
Speaker 1: noticed that in most versions of the periodic table, each
Speaker 1: square has a little number printed in its upper right
Speaker 1: hand corner. That figure is known as the atomic number.
Speaker 1: It tells the reader how many protons are in the
Speaker 1: atomic nucleus of a given element. For example, Oxygen's atomic
Speaker 1: number is eight. Every oxygen atom in the universe has
Speaker 1: a nucleus with exactly eight protons, no more, no less.
Speaker 1: Without this very specific arrangement of particles, oxygen wouldn't be oxygen.
Speaker 1: Each elements atomic number, including oxygen's, is totally unique, and
Speaker 1: it's a defining trait. No other element has eight protons
Speaker 1: per nucleus. By counting the protons, you can identify an atom.
Speaker 1: Just as oxygen atoms will always have eight protons, nitrogen
Speaker 1: atoms invariably come with seven. It's that simple neutrons do
Speaker 1: not follow suit the nucleus, and an oxygen atom is
Speaker 1: guaranteed to harbor eight protons as we've established, However, it
Speaker 1: might also contain anywhere from four to twenty neutrons. Isotopes
Speaker 1: are variants of the same chemical element that have different
Speaker 1: numbers of neutrons. Now, each isotope is named on the
Speaker 1: basis its mass number, which is the total combined number
Speaker 1: of neutrons and protons in an atom. For example, one
Speaker 1: of the better known oxygen isotopes is called oxygen eighteen
Speaker 1: because it's got the standard eight protons plus ten neutrons.
Speaker 1: A related isotope, oxygen seventeen, has one fewer neutron in
Speaker 1: the nucleus. Some combinations of subatomic particles are stronger than others.
Speaker 1: Scientists classify oxygen seventeen and eighteen as stable isotopes. In
Speaker 1: a stable isotope, the forces exerted by the protons and
Speaker 1: neutrons hold each other together permanently, keeping the nucleus intact
Speaker 1: on the flip side. The nuclei in radioactive isotopes, also
Speaker 1: called radio isotopes, are unstable and will decay over time.
Speaker 1: These things have a protons neutron ratio that's fundamentally unsustainable
Speaker 1: in the long run. Nobody wants to stay in that predicament. Hence,
Speaker 1: radioactive isotopes will shed some subatomic particles and release energy
Speaker 1: while they're at it until they've converted themselves into nice
Speaker 1: stable isotopes. So oxygen eighteen is stable, but oxygen nineteen
Speaker 1: is not. The latter will inevitably break down and fast
Speaker 1: within twenty six point eight eight seconds of its creation.
Speaker 1: Any given sample of oxygen nineteen is guaranteed to lose
Speaker 1: half of its atoms to the ravages of decay. That
Speaker 1: means of oxygen nineteen has a half life of twenty
Speaker 1: six point eight eight seconds. A half life is the
Speaker 1: amount of time it takes of an isotope sample to decay.
Speaker 1: Remember this concept, we're going to connect it to paleontology
Speaker 1: in just a minute. But before we talk about fossil science,
Speaker 1: there's an important point that needs to be made. Unlike oxygen,
Speaker 1: some elements do not have any stable isotopes whatsoever. Consider
Speaker 1: uranium in the natural world. There are three isotopes of
Speaker 1: this heavy metal, and they're all radioactive. With the atomic
Speaker 1: nuclei in a constant state of decay. Eventually a chunk
Speaker 1: of uranium will turn into it altogether different element. Don't
Speaker 1: bother trying to watch the transition in real time, though
Speaker 1: the process unfolds very very slowly. Uranium two thirty eight,
Speaker 1: the elements most common isotope, has a half life of
Speaker 1: about four point five billion years. Gradually it will become
Speaker 1: lead to OH six, which is stable. Likewise, uranium two
Speaker 1: thirty five, with its seven hundred and four million year
Speaker 1: half life, transitions into lead to OH seven, another stable isotope.
Speaker 1: Two geologists, this is really useful information. Let's say somebody
Speaker 1: finds a slab of rock whose zircon crystals contain a
Speaker 1: mixture of uranium two thirty five and lead to OH seven.
Speaker 1: The ratio of those two atoms can help scientists determine
Speaker 1: the rocks age. Here's how Let's say the lead atoms
Speaker 1: vastly outnumber their uranium counterparts. In that case, you know
Speaker 1: you're looking at a pretty old rock. After all, the
Speaker 1: uraniums had plenty of time to start transforming itself into lead.
Speaker 1: On the other hand, if the opposite is true, and
Speaker 1: the uranium atoms are more common, then the rock must
Speaker 1: be on the younger side. The technique we've just described
Speaker 1: is called radiometric dating. That's the act of using the
Speaker 1: well documented decay rates of unstable isotopes to estimate the
Speaker 1: age of rock samples and geologic formations. A Paleontologists have
Speaker 1: harnessed the strategy to determine how much time has elapsed
Speaker 1: since a particular fossil was deposited, though it's not always
Speaker 1: possible to date the specimen directly. You don't need to
Speaker 1: be a prehistory buff to appreciate isotopes. Medical practitioners use
Speaker 1: some of the radioactive varieties to monitor blood flow, study
Speaker 1: bone growth, and even fight cancer. Radio Isotopes have also
Speaker 1: been used to give farmers insights into soil quality. So
Speaker 1: there you have it. Something as seemingly abstract as the
Speaker 1: variability of neutrons affects everything from cancer treatment to the
Speaker 1: mysteries of deep time. Science is awesome. Today's episode was
Speaker 1: written by Mark Mancini and produced by Tyler Clang. Brain
Speaker 1: Stuff is a production of iHeart Radio's How Stuff Works.
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