- [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.