The uncertain location of electrons - George Zaidan and Charles Morton

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The tiny atoms that make up our world are made up of even tinier protons, neutrons and electrons. Though the number of protons determine an atom's identity, it's the electrons -- specifically, their exact location outside the nucleus -- that particularly perplex scientists. George Zaidan and Charles Morton show how to make an educated guess of where those itty-bitty freewheeling electrons might be.

Lesson by George Zaidan and Charles Morton, animation by Karrot Animation.

You probably know that all stuff
is made up of atoms

and that an atom

is a really, really, really,
really tiny particle.

Every atom has a core,

which is made up of at least one

positively charged particle

called a proton,

and in most cases,

some number of neutral
particles called neutrons.

That core is surrounded

by negatively charged
particles called electrons.

The identity of an atom is determined

only by the number
of protons in its nucleus.

Hydrogen is hydrogen because it
has just one proton,

carbon is carbon because it has six,

gold is gold because it has 79,

and so on.

Indulge me in a momentary tangent.

How do we know about atomic structure?

We can't see protons,
neutrons, or electrons.

So, we do a bunch of experiments

and develop a model
for what we think is there.

Then we do some more experiments

and see if they agree with the model.

If they do, great.

If they don't, it might
be time for a new model.

We've had lots of very
different models for atoms

since Democritus in 400 BC,

and there will almost certainly

be many more to come.

Okay, tangent over.

The cores of atoms tend to stick together,

but electrons are free to move,

and this is why chemists love electrons.

If we could marry them,

we probably would.

But electrons are weird.

They appear to behave either as particles,

like little baseballs,

or as waves, like water waves,

depending on the experiment
that we perform.

One of the weirdest things about electrons

is that we can't exactly
say where they are.

It's not that we don't have the equipment,

it's that this uncertainty

is part of our model of the electron.

So, we can't pinpoint them, fine.

But we can say
there's a certain probability

of finding an electron in a given space

around the nucleus.

And that means that we can
ask the following question:

If we drew a shape around the nucleus

such that we would be 95% sure

of finding a given electron
within that shape,

what would it look like?

Here are a few of these shapes.

Chemists call them orbitals,

and what each one looks like

depends on, among other things,

how much energy it has.

The more energy an orbital has,

the farther most of its density is

from the nucleus.

By they way, why did we pick 95%

and not 100%?

Well, that's another quirk

of our model of the electron.

Past a certain distance from the nucleus,

the probability of finding an electron

starts to decrease

more or less exponentially,

which means that while it
will approach zero,

it'll never actually hit zero.

So, in every atom,

there is some small,
but non-zero, probability

that for a very, very
short period of time,

one of its electrons

is at the other end of the known universe.

But mostly electrons stay
close to their nucleus

as clouds of negative charged density

that shift and move with time.

How electrons from one atom

interact with electrons from another

determines almost everything.

Atoms can give up their electrons,

surrendering them to other atoms,

or they can share electrons.

And the dynamics of this social network

are what make chemistry interesting.

From plain old rocks

to the beautiful complexity of life,

the nature of everything we see,

hear,

smell, taste, touch, and even feel

is determined at the atomic level.