Protons, neutrons, and electrons in atoms | Atomic structure | High school chemistry | Khan Academy

- [Instructor] Everything in
our world is made up of atoms.

Yep, everything.

From the air we breathe
to the water we drink,

even the materials inside our cellphones.

But what are atoms exactly?

What's inside of these atoms?

What makes an atom an atom?

Atoms are tiny particles that
are basic units of matter,

like building blocks.

But atoms themselves are made up

of even smaller subatomic particles,

called protons, neutrons, and electrons.

Let's take a look at
the simplified diagram

to learn more about
these subatomic particles

and the structure of an atom.

In the center of an atom,
we have the nucleus,

which is composed of protons and neutrons.

Outside the nucleus, we
have the electron cloud.

This is where electrons are
most likely to be found.

I've drawn the nucleus much
larger than it really is,

but an atom's electron cloud can be

100,000 times larger than its nucleus.

So the electron cloud actually makes up

most of the atom's volume.

Protons, neutrons, and electrons differ

in terms of their charge and mass.

Let's take a look at charge first.

Protons have a positive
charge of one plus,

and electrons have a
negative charge of one minus.

These charges are equal and opposite,

so when protons and electrons
are paired in atoms,

their charges cancel.

Neutrons have no charge,
which means they are neutral.

What about mass?

The unit we use to express the masses

of subatomic particles is
the unified atomic mass unit,

abbreviated as U.

Protons and neutrons have
a similar mass about one U.

In comparison, electrons have a mass

of about 0.0005 U,

which makes them roughly
2,000 times smaller

than either a proton or a neutron.

This means that nearly all the mass

of an atom resides in the nucleus,

and not in the electron cloud.

Atoms make up everything in our world,

even though the air we
breathe, the water we drink,

and the cellphones we use all look

really different from one another,

the atoms that make up these
things are all composed

of the same subatomic particles;

protons, neutrons, and electrons.