>> Welcome to the video lecture on the electrons.
Atoms and Elements, Part 2B.
We are going to take and build off of the nucleus,
and look at what's going
on around the nucleus with the electrons.
Let's get started.
Alright, so as we remember, right?
When we look at the macroscopic level,
we can say that matter is anything with mass and volume.
And that's why density's such a big deal.
And now that we've studied the nucleus,
we realize that the protons and the neutrons
in the nucleus are what create the mass of matter.
And so this is all at the atomic level.
And now what we're going to learn is
so where does the volume of matter come from?
Well, it comes from the electrons, right?
Because those are outside the nucleus.
Okay, and so this volume, right?
This is what creates atomic size.
Alright. So what else do we know about electrons?
Well, we know that opposites attract.
So the negative charge on the electrons, right?
Is attracted to the positive charge of the nucleus.
Which of course is the protons.
So that's what holds the atom together.
This electrostatic attraction, right?
But at the same time, we know that electrons repel each other.
Alright? And we also know that electrons are constantly moving.
And that's what gives the illusion
of a solid aspect to matter.
Because essentially we've learned
that matter is hollow, right?
The nucleus is the size of a grape.
The electrons are up to a mile away.
So most of an atom is empty space.
But it feels -- right?
The counter feels hard because electrons move constantly.
Alrighty. So we have this attraction and repulsion.
So we can think of electronic structure
as basically a peace agreement between electrons.
They want to share the nucleus, so they're willing
to hang out with each other.
Over time, we've learned that electrons travel mathematically
in these defined regions.
And there's a lot of calculous
and advanced mathematics that goes into that.
The good news is we don't really have
to worry too much about that.
We can focus on the highest order, which is the shells.
And so since our goal is biochemistry,
the shell model is enough for us.
If you've taken chemistry before,
or you go on to take other chemistry courses,
then you'll learn about subshells and orbitals.
But for our course, we don't really need those to get
to the biochemistry that's most relevant to our future.
Alrighty. So this N, right?
I think it's pretty logical, right?
As N increases -- as the value of N goes up --
the electron energy also increases.
So we have a direct relationship there.
And if as we -- electrons have more energy,
that means they are moving more in a bigger space,
we get a larger atomic size.
So fortunately, everything's a direct relationship.
So let's look at three atoms.
Right? So here's our buddy hydrogen.
And we know it has one proton.
There's the nuclear charge.
Here's our buddy helium.
Two protons.
And then lithium with three protons, alright?
And because the atoms are neutral, we know that the number
of protons is going to equal the number of electrons,
because these are neutral atoms.
Okay, so since hydrogen has one proton,
there's its one electron floating around.
Right there.
And then helium would have the two electrons.
And then finally, lithium has the three electrons.
And now we get into the whole idea of the shells, right?
The first shell has room for the first two electrons,
and then it's full.
So then, for example, with lithium,
the third electron then goes into a larger shell, right?
Higher number of N, right?
More energy; bigger size.
Alright. So let's keep going.
Alrighty. So quite logically then, right?
As the shell number goes up, the more electrons can be held.
And there is enough medical algorithm --
I don't think it's worth memorizing.
We're just kind of building your knowledge here.
And we're really going to focus
in this course on the second shell.
And so let's work through the algorithm, right?
And so the algorithm has a 2 for everybody, right?
There's the 2 and then here's our N squared.
So 1 squared, right?
So as we saw on the previous page, right?
That first shell could only hold two electrons.
When we get to the second shell, we can get 8.
And then this is a big deal, right?
Because 8's the octet.
And that's going to be a focus of our course.
And so that's the main reason for going
through the algorithm is to see where we come up with the 8.
Just to finish the pattern here, right?
The third shell can hold 18.
We would look a little bit here
because of phosphorous and sulfur.
Those are our third shell elements.
But here, carbon, nitrogen, oxygen will be our second shell.
And of course our buddy -- oops rolling pins --
hydrogen is a first shell.
Okay. And then last but not least,
just to finish out the pattern.
If we had elements that had electrons in the fourth shell,
that shell can hold 32 electrons.
Okay. So because the electrons are in different shells,
they are not all created equal.
This is a really important concept.
The valance electrons, those are the outermost electrons.
These are the electrons that can be gained, lost, or shared.
As we continue through the course,
we will see that when they're gained or lost, right?
This is when ions form.
And if they're shared, right?
Then that -- this would be a covalent bond.
All right?
So this is building up for us.
And then the core electrons,
these are the innermost electrons.
These are the inner electrons.
And these are pretty boring.
They are tightly held by that positively charged nucleus.
So they don't get to go anywhere.
They live a pretty boring life on the chemical level
because they're trapped.
So the emphasis on our course will be up here
at these valence electrons.
This is where chemistry happens.
So let's put this altogether with a lithium atom.
And make sure that we understand all the terms
and how everything works together.
So here we go.
We've got the whole thing.
Alright. So it's a lithium atom.
Alright? So what do we know about lithium?
Right, it has three protons.
So it's going to have three electrons.
So here, right?
This would be our N = 1 shell, right?
With two electrons.
And then there is our N = 2 shell.
And it only has one electron.
And then of course here is our nucleus.
Alright? So to make sure that we understand the vocabulary,
right?
So how many electrons are in the valence shell, right?
So valence is outermost.
So there's only one electron in the valence shell.
How many inner shell or core electrons do we have?
There's our two right there.
Alright? And then just to kind of loop back through some
of our atomic structure, right?
Protons. Three neutrons, right?
There's our mass number, right?
That 6 is the protons plus the neutrons.
So 6 - 3 tells us that we would have 3 neutrons.
So making sure that we're clear here, right?
So here's our valence.
And here's our core.
And then there's our nucleus
with three protons and three neutrons.
Alrighty. So that wraps up our introduction to electrons.
This would be a great time to go ahead
and work those post-video practice problems
to reinforce your understanding.