- [Voiceover] So, let's talk a little bit about
a word you might have heard and that is Ion.
Let's talk about what it is and then we'll talk about
trends in the periodic table on,
on I guess how hard it is to make something an Ion.
In particular how hard it is
to make something a positive ion.
So, an ion is just an atom or a molecule
that has charge and it'll have charge if the
protons are not equal to the electrons.
Neutrons are obviously also constituent of atoms
but neutrons are neutral.
What you're gonna get your charge
from are your protons or electrons.
So, you're going to have a net charge.
If your number of, number of protons,
and this is for an atom or molecule.
A molecule's just a bunch of,
a bunch of atoms bonded together.
If the number of protons does not equal
the number of electrons.
And you can have positive ions if the protons are
more than the number of electrons, protons,
or positive electrons or negative.
And you can have negative ions if the number
of electrons are greater than the number of protons.
For example, for example, if you just had
Hydrogen in it's neutral state
has one proton and one electron,
but if you were to take one of those electrons away
then Hydrogen would have a positive charge
and essentially it would just be,
in its most common isotope it would just
be a proton by itself.
And so, when we talk about a positive ion like this
where our protons are more than our electrons,
the number of protons are more than the number of electrons,
we call these cations, cations.
Cation, once again, just another word positive ion.
Likewise, we can have negative ions.
So, say for example, Fluorine.
So, Fluorine gains an electron,
it's going to have a negative charge.
It's gonna have a negative charge of negative one,
and a negative ion we call an anion.
And the way that I remember this is
a kind of means the opposite or the negation of something.
So, this is a negative ion.
We've negating, you can somehow
think we are negating the ion.
So, with that out of the way,
let's think about how hard it will be ionize
different elements in the periodic table.
In particular, how hard it is to turn them into cations.
And to think about that, we'll introduce
an idea called ionization energy.
Ionization...
Ionization energy...
Energy...
And this is defined, this is defined as
the energy required, energy required
to remove an electron, to remove an electron.
So, it could've even been called cationization energy
because you really see energy required to remove
an electron and make the overall atom more positive.
So, let's think about the trends.
And we already have a little bit of background
on the different groups of the periodic table.
So, for example, if we were to focus on,
especially we could look at group one,
and we've already talked about how Hydrogen's
a bit of a special case in group one
but if we look at everything below Hydrogen.
If we look at the Alkali, if we look
at the Alkali metals here
we've already talked about the fact
that these are very willing to lose an electron.
Why? Because if they lose an electron
they get to the electron configuration
of the noble gas before it.
So, if Lithium loses an electron
then it has an outer shell electron configuration of Helium.
It has two outer electrons and that's kind of,
we typically talk about the Octet Rule
but if we're talking about characters like Lithium or Helium
they're happy with two 'cause you can
only put two electrons in that first shell.
But all the rest of 'em, Sodium, Potassium, etc., etc.,
if you take an electron away from them
then their outermost shell,
well, all of them in their outermost shell
they're going to have the electron configuration
of the noble gas before it
and for Sodium on down that outer shell
is going to have that perfect eight.
Lithium, if you remove an electron,
it would get to Helium and it would have
two electrons in its outer shell.
So, you can imagine that the ionization energy
right over here, the energy required to remove electrons
from your Alkali Metals is very low.
So, let me just write down this is...
So, when I say low, I'm talking about low ionization energy.
Low.
Now, what happens as we move to the right
of the periodic table?
In fact, let's go all the way
to the right on the periodic table.
Well, if we go here to the Noble Gases,
the Noble Gases we've already talked about.
They're very, very, very stable.
They don't want no one,
they don't want their electron configurations messed with.
So, it would be very hard...
Neon on down has their eight electrons
that (mumbling) Octet Rule.
Helium has two which is full for the first shell,
and so it's very hard to remove an electron from here,
and so it has a very high ionization energy.
Low energy, easy to remove electrons.
Or especially the first electron,
and then here you have a high ionization energy.
I know you have trouble seeing that H.
So, this is high, high ionization energy,
and that's the general trend across the periodic table.
As you go from left to right,
you go from low ionization energy to high ionization energy.
Now, what about trends up and down the periodic table?
Well, within any group, if we,
even if we look at the Alkali,
if we look at the Alkali Metals right over here,
if we're down at the bottom,
if we're looking at, if we're looking at,
say, Cesium right over here,
that electron in the, one, two, three, four, five, six,
in the sixth shell, that's going to be
further from that one electron
that Lithium has and its second shell.
So, it's going to be, it's going to be further away.
It's not going to be as closely bound to the nucleus,
I guess you could say.
So, this is going to be even,
that one electron's gonna even easier to remove
than the one electron in the outermost shell of Lithium.
So, this one has even lower, even lower,
even lower...
And that's even going to be true of the Noble Gases out here
that Xenon, that it's electrons in its outermost shell,
even though it has eight valence electrons,
they're further away from the nucleus,
and so they're a little, the energy required
to remove them is still going to be high
but it's going to be lower than the energy from,
from say Neon or Helium.
So, this is low.
So, once again, ionization energy low to high
as we go from left to right,
and low to high as we go from bottom to top.
Or we could say a general trend
that if we go from the bottom left to the top right
we go from low ionization energy,
very easy to remove an electron
from these characters right over here
to high ionization energy,
very hard to move, remove an electron
from these characters over here.
And you can see it if, you could see
in a trend of actual measured ionization energies
and I like to see charts like this because
it kind of show you where the periodic table came from
when people noticed these kind of periodic trends.
It's like, hey, it looks like
there's some common patterns here.
But on this one in particular we see on this axis
we have ionization energy and electron volts,
that's actually, it's literally a,
this is units of energy.
You could convert it to Joules if you like.
Then over here, we're increasing the atomic numbers.
So, we're (mumbling), we're starting with
Hydrogen then we go to Helium,
and we keep, and then we go,
go from Hydrogen to Helium to Lithium
and let me show you what's happening right over here.
So, you go to Hydrogen to Helium.
So, Helium here is very stable,
so it's very hard to remove an electron.
And then you go to Lithium.
Lithium, as we said, this is an Alkali metal.
You remove an electron, it gets to a stable state.
So, it takes very low energy to remove that electron.
And then as we go from left to right on the periodic table,
as we go from Alkali Metal to Noble Gases
we see that the ionization energy increases.
And there are these little dips here
which you could think about why these...
(mumbling) Or theorize why these dips are occurring,
what you see in this general trend
as we go from Alkali Metals to Noble Gases.
Alkali Metals to Noble Gases.
Now, one thing you might be saying is,
"Hey, look, you had from here to here,
"that's the same distance as here to here,
"but now we have a larger distance here.
"What's going on here?"
Well, we have to remember now we
have all of our D block elements.
So, now, once we get, once we get to the,
once we get over here we're now adding
all of the D block elements.
(mumbling) On the fourth period
and so we have those, we have those added here,
so you have D block elements, D block elements,
and then here you have you F and D block elements.
And so, you see the general trend
that your Alkali, your Alkali Metals
are very low ionization energy.
Your Noble Gases, very high ionization energy.
But as they get, as the atoms get larger and larger
the ionization energy goes lower and lower,
and sends something like Radon,
which even though it's Noble Gas
it's ionization energy because those outermost electrons
are further away from the nucleus
or they're quite far away from the nucleus,
that its ionization energy is actually,
its ionization energy is
actually less then that of Hydrogen.
Anyway, hope you found that interesting.