I'm going to take you on a tour of an atom so that you can see how tiny and empty it is.
The Great Pyramid of Giza is estimated to have a mass of about 5.2 billion kilograms. If we were
to squeeze all of the empty space out of it and just have the subatomic particles close together,
it would be about the size of a single grain of rice. If we were to scale an atom up to the size
of this baseball this is what it would look like: Nothing. Because atoms are mostly empty space and
even at this scale the subatomic particles are too small to see. Instead, let's scale the nucleus up
to be the size of this baseball. This particular nucleus contains six protons and six neutrons,
making it a carbon-12 nucleus. It is extremely dense. It contains about 99.97% of the entire
mass of our atom. If this baseball had the same density as a nucleus, its mass would be 6.64
times 10 to the 13th kilograms. That's the mass of about 12,700 Great Pyramids of Giza.
There are six electrons zooming around out there somewhere in orbitals that make up the remaining
0.03% of the mass. Let's go find them. Electrons don't orbit the nucleus the same way that planets
orbit around the sun. The subatomic particles in a stable nucleus usually stick together but
the electrons are free to move. We're uncertain of their locations but what about probable locations?
If we could draw a shape around the nucleus that a given electron spends 90 percent of its time in,
what would it look like? These shapes are called atomic orbitals and here are a few of them.
An atomic orbital is a region of space with a high probability of having electrons in it. They come
in different shapes and sizes but our carbon atom only has s and p orbitals. Why did we pick 90%
and not 100%? Well, beyond these 90% boundaries the probability of finding an electron gets
exponentially lower as we get farther away, but it never goes to zero. It is possible that for
an extremely small period of time the electron will be on the opposite side of the universe
compared to the atom it's orbiting. I can't ride my bike that far so you're getting a 90% boundary.
I've done my math based on an atom of carbon-12. We're increasing the radius by a factor of 1.49
times 10 to the 13th power. We're only looking for the first two electrons right now you are not
going to like how we'll know when we found them. I'll get to that a little later. Electrons move
at about 2.2 million meters per second. That's fast enough to orbit the Earth in 18 seconds.
There's a lot of debate among physicists about how to measure the size of electrons,
but they're difficult or impossible to see even at this scale. I've now biked 1.27 kilometers from
our nucleus. This particular distance from the nucleus is a node. A node is a region with zero
probability of housing electrons, which makes this a good safe place to slow down and talk.
So far, I've biked from the nucleus along a radius of the 1s orbital. This is our first and smallest
s orbital. This orbital is spherical, centered on our baseball back at the start and home to
two electrons. Those two electrons spend 90% of their time in this sphere. Let's go look for
the next batch of electrons while I tell you how we were able to notice the first two electrons.
Beta radiation actually consists of electrons. Finding these electrons will result in symptoms
of beta radiation exposure: Within hours, we'd have symptoms that are a lot like a sunburn.
Then there's a latent stage where no injury is evident, but a few days or weeks later,
illness can start to manifest. The basal layer of skin that was damaged originally
is repopulated through the division of surviving cells. This stage begins with
the same sunburn-like symptoms as earlier, but it can get worse depending on the dose of radiation.
You could just have increased pigmentation and dry skin or you could have damage to the blood
vessels that leads to pain, a bluish color to the skin, and eventually necrosis, meaning death
of body tissue. Years later you could still be dealing with problems like pain and skin cancer.
This was all on a normal size scale, where beta radiation can't penetrate to our internal organs.
If the electron penetration depth scales up in this imaginary huge atom that we're touring,
we'd be in a lot more trouble. At this scale, electrons can penetrate into our internal organs
and cause these health effects throughout our bodies, not just on our skin.
I'm now 2.54 kilometers from the nucleus and this is another node. The region that
we just passed through was the valence shell of the carbon atom and that's where most of
the chemistry occurs. The valence shell of any atom is the outermost shell of electrons and
most chemistry occurs there because it's the most easily accessible to the outside world.
There were two more electrons in a spherical 2s orbital that we just passed through. I'm also
potentially near the outer bounds of a 2p orbital containing 1 electron. The p orbitals are dumbbell
shaped, not spherical, so at this distance from the nucleus I'm at the tip of a 2p orbital. p
orbitals come in groups of 3, each 90 degrees from each other, but they are not all filled in
this carbon atom. As for the last electron, I would have needed to travel this same distance
from the nucleus but in a different direction. It would have been in a different 2p orbital. Now,
I'm going to travel all around the world using the magic of edi-//-agic of editing to show you
the scale of this carbon atom in famous locations: from a baseball diamond in Central Park, New York
to the top of Mount Fuji, which I totally climbed just for the purpose of this video
to the Colosseum in Rome.
To show you just how tiny atoms are: If we were to take the width of a human hair and
scale it up by the same factor that we've been using, its diameter would be the size
of -- not the moon -- but the moon's orbit around the Earth. And a penny would scale up
to the size of the Earth's orbit around the Sun. So the next time you touch basically anything,
remember that it's mostly empty and its atoms are tiny. Thanks for watching Chemistry in a
Nutshell. If you feel that I've earned it, please like this video and subscribe to my channel.