Atoms | Middle school chemistry | Khan Academy

- [Narrator] You're walking on the street

and suddenly you find a piece of gold,

you pick it up and you get super curious.

You have a lot of questions in your mind.

One of the questions is,

what happens if you were to break it?

I mean, surely you can't
break it with your own hands

but hey, when has that stopped you

from imagining things, right?

So what happens if you break this?

Well, you get two pieces of
gold and then you wonder,

well, what if you break it even further?

You get even more smaller pieces.

And what if you break it even further?

We get even more smaller pieces.

And now you start wondering,
"Hey, can I keep doing that?"

Can I keep breaking this
piece of gold forever?

That's what we we're gonna
talk about in this video.

This was a question

that many ancient philosophers
from India, Greece, Roman,

probably many more, pondered upon.

They wondered, if you take any element,

remember what elements are?

These are roughly about
100 building blocks

that make up all the
matter in the universe

gold is an example of them.

So they wondered, if you take any element,

could you keep breaking them down forever?

And a lot of them thought,
that maybe the answer is no.

Maybe you can't keep breaking it forever.

Maybe eventually, you will get

one last smallest piece of that element,

a smallest piece of gold, for example,

which you cannot break any further.

A lot of people believed in this idea,

and the Greeks actually named
this smallest piece, the atom.

The word atom literally means uncuttable

because they believe that you
cannot break this even more.

Now, for a long time,

many people didn't believe in this idea.

So for centuries, the idea
of atom was suppressed

until it was revived back by
scientists like John Dalton.

And today we have plenty of
evidence that they do exist.

So, what exactly are atoms?

Well, think of atoms as the
smallest piece of an element

that has all the
properties of that element.

It is literally the building
block of the element itself.

For example, what's a gold atom?

Gold atoms are the
smallest pieces of gold,

which has all the properties of gold.

They're the building blocks of gold.

What's a carbon atom?

Well, they are the
smallest pieces of carbon

They're the building blocks of carbon.

They have all the properties of carbon.

And just to give you another
example, what's mercury atom?

They're the smallest pieces of mercury.

They have all the properties
of the element mercury

and so on and so forth.

Now, one question you could be having is,

do atoms look like tiny balls?

And the answer is no, it's
just a representation.

In reality, atoms are so incredibly tiny,

we can't even see them with microscopes.

So how tiny are they you ask?

Well, their size is
incredibly hard to comprehend.

So here's a way to think
about it, how many gold atoms

do you think you will find
in a typical gold ring?

Well, it's not millions, not
billions, it's sextillions

that's one followed by 21 zeros,

that many atoms you'll
probably find in a gold ring.

And just to get a sense of this number

scientists estimate that
that is roughly about

the total number of stars
in the observable universe.

Let that sink in. That's
how small atoms are.

So long story short, almost
all the matter in the universe,

from the microbes to dogs and cats,

to mountains to planets and stars,

and almost everything that
you see in this universe,

they're all fundamentally
made of elements.

These are the building blocks

of all the matter in the universe.

We have about 100 of them.

But what are elements
fundamentally made of?

Elements like gold or any
other element for that matter

they are fundamentally made of atoms.

They are the smallest
pieces of the elements,

the building blocks of the elements

that contain all the
properties of that element.