The New Alison App has just launched Download Now
We'll email you at these times to remind you to study
You can set up to 7 reminders per week
We'll email you at these times to remind you to study
In the last video we talked about how every atom really
wants to have eight-- let me write that down-- eight
electrons in its outermost shell.
This is kind of the most stable configuration that an
electron can have. And given this fact that's been
determined just by observing the world, really, we can
start to figure out what's likely to happen in different
groups of the periodic table.
A group of a periodic table is just a column of
the periodic table.
Like this group, right here, and actually I'll start with
this group, because it's got a special name.
This group right here is called the noble gases.
And what's common when you go down a group in
the periodic table?
What's common about a column in the periodic table?
Well, in the last video we saw that every element in a column
has the same number of valence electrons.
Or it has the same number of electrons in
its outermost shell.
And we figured out what that was.
This column, right here, which we learned were the alkali
metals, this has one electron in its outermost shell.
And I made that one caveat that hydrogen isn't
necessarily considered an alkali metal.
One, it's usually not in metal form.
And it doesn't want to give away electrons as much as
other metals do.
When people talk about metal-like characteristics of
an element, they're really talking about how likely it is
to give away electron.
We'll talk about other characteristics of a metal,
especially the way that we perceive metals as being
shiny, and maybe they conduct electricity, and see how that
plays out in the periodic table.
But anyway, back to what I was talking about.
This column, right here, this is called the
alkaline earth metals.
So this is alkaline earth.
These all have two atoms in its outermost shell.
So remember, everyone wants to get to eight.
If these guys wanted to get to eight by adding electrons,
they would have a long way to go.
This way, we would have to add seven electrons.
They would have to add six electrons.
And who are they going to take it from?
Because these guys don't want to give away their electrons.
They're so close to getting to eight.
So it's much easier when you're on the left-hand side
of the periodic table to give away electrons.
In fact, when you only have one to give away-- especially
in the case of elements other than hydrogen-- when you only
have one to give away, it really wants to do that.
And because of that, these elements right here are very
seldom found in their elemental state.
When I say elemental state, it means there's nothing but
lithium there, there's nothing but sodium there, there's
nothing but potassium there.
They're very likely, if you find this, it's probably
already reacted with something.
Probably with something on this side of the periodic
table, because this wants to give away something really
bad, this wants to take something really bad.
So the reaction will probably happen.
These are still reactive.
The alkaline earth metals are still reactive, but not as
reactive as the alkali metals.
And that's because these guys are really close to getting to
the stable magic eight number.
These guys are a little bit further away.
So it takes a little bit more, I guess you could say, of a
push for them to give away two.
These guys only have to give away one.
And then we learned that this has two in
its outermost shell.
And then all of these elements, which are called the
transition metals, as you add electrons, they're just
backfilling the previous shell's d subshell.
So their outermost shell still has two.
It still has those.
If this is the fourth period, all of these elements'
outermost shell has 4s2.
And these elements are just backfilling their 3d
Or their 3d subshell.
These are 2's.
So these all have two outermost electrons.
So all of these, like the alkaline earth metals, need to
lose two electrons in order to, quote-unquote, be happy.
And the way I think about this, and this is really just
a way-- and it maybe it bears out in physical reality-- is
that these guys have kind of a deep bench of electrons.
That if they are able to shed some of these valence
electrons-- so if I write iron has two valence electrons like
that-- even if they shed these electrons, they kind of have a
reserve of electrons in the d subshell for
the previous shell.
So if it sheds its 4s2 electrons, it still has all
those 3d electrons that have a high energy state that can
maybe kind of replace them.
And I'll use everything in quotation marks, because these
are just ways for me to visualize things.
And the reason why I make that point is because metals are
just very giving with their electrons.
And these guys react.
They say, hey, take my electrons.
These guys say, take these two electrons.
And these guys, they start to say, especially as you fill
the d subshell, I've got these two electrons, and not only do
I have those two electrons, but I have more electrons
where-- well almost where-- that came from.
I have some in reserve in my d.
And what happens in these transition metals, and it
especially happens in the metals-- so these are the
metals right here, and these don't follow just a group, but
this is the metals, this color right here-- is that they have
so many electrons to hand off, not only do they have these
extra there, but they filled their d subshell, that they
can kind of, especially when they're in elemental form, and
when I say elemental form, this means that you just have
a big block of aluminum.
Aluminum hasn't reacted with anything like oxygen.
It's just a bunch of aluminum.
When you have a bunch of aluminum, what happens is you
have these metallic bonds where all of the aluminum
atoms say, you know what, I have all these extra, I have
definitely, in the case of aluminum, three electrons in
my outermost shell.
But I have all of these kind of backfilled electrons in my
I'm just going to share them with the other aluminum atoms.
So you create this sea of aluminum atoms. And they're
attracted to each other.
Or you create this sea of aluminum electrons.
So you have a bunch of electrons sitting in between
the atoms, and since the atoms kind of donated these
electrons, they're attracted to them.
So the actual atoms-- so this would be an aluminum plus, and
maybe we would have donated three electrons.
But I'm not being exact here.
I want to just give you the sense of how things work.
And that's why metals conduct really well, because
electricity is just a bunch of electrons moving, and in order
to have electrons moving, you have to have surplus electrons
So elements right around this area are really good
In fact, silver is the best conductor.
Silver, right here, is the best conductor on the planet.
And the reason why that's not used for our wiring and copper
is because copper is easier to find than silver.
But silver is the best conductor.
And the way I think about it is that these-- once you've
filled an orbital, that orbital
becomes somewhat stable.
So all of these guys have filled their d orbital.
While these guys, their d orbital is not filled.
So they just have a lot of surplus electrons that are
really good for conduction.
Now, that's just an intuition.
I haven't done the experiment to prove that.
But it'll give you a sense of why things
conduct and all of that.
So these are the transition metals.
These are actually considered the metals.
But the reason why these are considered the transition
metals is because they're filling the d-block.
But transition metals kind of sound like not
as good as a metal.
But when I think of metals, iron is kind of the first
metal I always think of.
I definitely think of silver and copper and gold as metals.
So to call them transition metals is a little not fair.
I don't really consider aluminum more of a metal than,
let's say, iron is.
But in chemistry classification world, aluminum
is more of a metal.
These elements right here.
And I know I dropped off come from kind of the group notion.
But let me just actually write the valence electrons.
So these all have three valence electrons.
Four, five, six, seven.
So these all have three electrons in
its outermost shell.
It still seems easier for them to give them away than to take
them, but maybe now, in certain cases, there could be,
especially in the case of, let's say, boron, there could
be a situation where it maybe could gain five electrons,
although that seems hard.
It's much easier to give away three and that's why a lot of
the, quote-unquote, official metals
show up in this category.
And as you can see, as you go down the periodic table you
can kind of have metals that have more and
more valence electrons.
So for, let's say, lead.
It's still a metal, even though it has
four valence electrons.
And that's because the atom is so big, its radius is so large
that the outermost shell is so far away from the nucleus,
that those electrons are easier to take off.
So for example, as you go down, carbon, those electrons
are very close to the nucleus.
So they're very hard to take off.
So carbon would probably more likely gain electrons from
somebody else to get to eight.
While these guys' valence electrons are so far away from
the nucleus that they're more likely to kind of want to get
rid of them to get to eight and get back to an electron
configuration of, let's say, xenon.
And you go and then these guys are the nonmetals.
They're likely to probably gain
electrons in most reactions.
And then this yellow category that I said was highly
reactive, especially highly reactive with the alkali
metals over here, these are called halogens.
And you've probably heard the word before.
That's no mistake there to call them halogen lamps.
That's not a random choice of words.
Maybe I'll do a video on halogen lamps in the future.
And then finally, we're at the noble gases.
What's interesting about the noble gases?
Well they have eight electrons in their
outermost shell, right?
Except for helium.
Helium has two, right?
Helium's electron configuration is 1s2.
But all of these other guys, this guy's electron
configuration is 1s2.
This is neon.
1s2, 2s2, 2p6.
So he has eight electrons in his outermost shell.
So he's happy.
Argon, same thing.
The outermost shell will look like 3s2, 3p6.
Krypton will have in its outermost shell
will be 3s2, 3p6.
It will also have some 3d electrons around as it
backfilled back here.
But all of these have eight in its outermost shell, so
They have no incentive to react.
They're kind of like, hey, all of you other elements, just,
you know, you guys can do all that crazy reactions that
you've got to do, but we're happy.
And we don't want to give or take electrons.
And because of that these guys are highly, highly unreactive.
Very, very unreactive.
And you know, back in the day, when they used to make these
kind of zeppelins, these big blimps-- the Hindenburg is a
famous example-- they used hydrogen.
And obviously hydrogen is a pretty reactive substance.
It's actually very combustible and that's why it blows up
very fast. And that's why now, clowns or children's balloon
manufacturers, they instead would prefer to use helium.
Because helium is a noble gas and it's very unreactive.
And it's very unlikely to explode at a
child's birthday party.
But anyway, I think I'm done now with this video.
And in the next video we'll talk a little bit more about
trends across the periodic table.
Log in to save your progress and obtain a certificate in Alison’s free Chemistry - Atoms, Elements and the Periodic Table online course
Sign up to save your progress and obtain a certificate in Alison’s free Chemistry - Atoms, Elements and the Periodic Table online course
Please enter you email address and we will mail you a link to reset your password.