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In the last video we talked about how every atom really

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wants to have eight-- let me write that down-- eight

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electrons in its outermost shell.

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This is kind of the most stable configuration than an

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electron can have. And given this fact that's been

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determined just by observing the world, really, we can

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start to figure out what's likely to happen in different

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groups of the periodic table.

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A group of a periodic table is just a column of

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the periodic table.

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Like this group, right here, and actually I'll start with

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this group, because it's got a special name.

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This group right here is called the noble gases.

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And what's common when you go down a group in

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the periodic table?

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What's common about a column in the periodic table?

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Well, in the last video we saw that every element in a column

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has the same number of valence electrons.

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Or it has the same number of electrons in

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its outermost shell.

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And we figured out what that was.

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This column, right here, which we learned were the alkali

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metals, this has one electron in its outermost shell.

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And I made that one caveat that hydrogen isn't

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necessarily considered an alkali metal.

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One, it's usually not in metal form.

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And it doesn't want to give away electrons as much as

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other metals do.

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When people talk about metal-like characteristics of

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an element, they're really talking about how likely it is

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to give away electron.

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We'll talk about other characteristics of a metal,

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especially the way that we perceive metals as being

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shiny, and maybe they conduct electricity, and see how that

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plays out in the periodic table.

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But anyway, back to what I was talking about.

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This column, right here, this is called the

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alkaline earth metals.

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So this is alkaline earth.

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These all have two atoms in its outermost shell.

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So remember, everyone wants to get to eight.

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If these guys wanted to get to eight by adding electrons,

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they would have a long way to go.

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This way, we would have to add seven electrons.

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They would have to add six electrons.

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And who are they going to take it from?

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Because these guys don't want to give away their electrons.

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They're so close to getting to eight.

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So it's much easier when you're on the left-hand side

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of the periodic table to give away electrons.

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In fact, when you only have one to give away-- especially

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in the case of elements other than hydrogen-- when you only

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have one to give away, it really wants to do that.

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And because of that, these elements right here are very

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seldom found in their elemental state.

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When I say elemental state, it means there's nothing but

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lithium there, there's nothing but sodium there, there's

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nothing but potassium there.

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They're very likely, if you find this, it's probably

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already reacted with something.

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Probably with something on this side of the periodic

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table, because this wants to give away something really

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bad, this wants to take something really bad.

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So the reaction will probably happen.

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These are still reactive.

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The alkaline earth metals are still reactive, but not as

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reactive as the alkali metals.

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And that's because these guys are really close to getting to

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the stable magic eight number.

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These guys are a little bit further away.

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So it takes a little bit more, I guess you could say, of a

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push for them to give away two.

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These guys only have to give away one.

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And then we learned that this has two in

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its outermost shell.

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And then all of these elements, which are called the

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transition metals, as you add electrons, they're just

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backfilling the previous shell's d subshell.

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Right?

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So their outermost shell still has two.

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It still has those.

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If this is the fourth period, all of these elements'

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outermost shell has 4s2.

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And these elements are just backfilling their 3d

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suborbital.

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Or their 3d subshell.

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These are 2's.

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So these all have two outermost electrons.

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So all of these, like the alkaline earth metals, need to

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lose two electrons in order to, quote-unquote, be happy.

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And the way I think about this, and this is really just

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a way-- and it maybe it bears out in physical reality-- is

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that these guys have kind of a deep bench of electrons.

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That if they are able to shed some of these valence

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electrons-- so if I write iron has two valence electrons like

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that-- even if they shed these electrons, they kind of have a

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reserve of electrons in the d subshell for

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the previous shell.

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So if it sheds its 4s2 electrons, it still has all

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those 3d electrons that have a high energy state that can

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maybe kind of replace them.

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And I'll use everything in quotation marks, because these

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are just ways for me to visualize things.

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And the reason why I make that point is because metals are

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just very giving with their electrons.

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And these guys react.

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They say, hey, take my electrons.

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These guys say, take these two electrons.

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And these guys, they start to say, especially as you fill

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the d subshell, I've got these two electrons, and not only do

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I have those two electrons, but I have more electrons

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where-- well almost where-- that came from.

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I have some in reserve in my d.

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And what happens in these transition metals, and it

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especially happens in the metals-- so these are the

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metals right here, and these don't follow just a group, but

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this is the metals, this color right here-- is that they have

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so many electrons to hand off, not only do they have these

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extra there, but they filled their d subshell, that they

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can kind of, especially when they're in elemental form, and

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when I say elemental form, this means that you just have

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a big block of aluminum.

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Aluminum hasn't reacted with anything like oxygen.

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It's just a bunch of aluminum.

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Right?

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When you have a bunch of aluminum, what happens is you

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have these metallic bonds where all of the aluminum

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atoms say, you know what, I have all these extra, I have

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definitely, in the case of aluminum, three electrons in

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my outermost shell.

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But I have all of these kind of backfilled electrons in my

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d suborbital.

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I'm just going to share them with the other aluminum atoms.

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So you create this sea of aluminum atoms. And they're

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attracted to each other.

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Or you create this sea of aluminum electrons.

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So you have a bunch of electrons sitting in between

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the atoms, and since the atoms kind of donated these

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electrons, they're attracted to them.

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Right?

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So the actual atoms-- so this would be an aluminum plus, and

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maybe we would have donated three electrons.

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But I'm not being exact here.

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I want to just give you the sense of how things work.

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And that's why metals conduct really well, because

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electricity is just a bunch of electrons moving, and in order

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to have electrons moving, you have to have surplus electrons

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lying around.

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So elements right around this area are really good

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conductors.

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In fact, silver is the best conductor.

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Silver, right here, is the best conductor on the planet.

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And the reason why that's not used for our wiring and copper

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is because copper is easier to find than silver.

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But silver is the best conductor.

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And the way I think about it is that these-- once you've

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filled an orbital, that orbital

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becomes somewhat stable.

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So all of these guys have filled their d orbital.

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While these guys, their d orbital is not filled.

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So they just have a lot of surplus electrons that are

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really good for conduction.

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Now, that's just an intuition.

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I haven't done the experiment to prove that.

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But it'll give you a sense of why things

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conduct and all of that.

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So these are the transition metals.

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These are actually considered the metals.

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But the reason why these are considered the transition

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metals is because they're filling the d-block.

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But transition metals kind of sound like not

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as good as a metal.

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But when I think of metals, iron is kind of the first

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metal I always think of.

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I definitely think of silver and copper and gold as metals.

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So to call them transition metals is a little not fair.

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I don't really consider aluminum more of a metal than,

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let's say, iron is.

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But in chemistry classification world, aluminum

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is more of a metal.

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These elements right here.

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And I know I dropped off come from kind of the group notion.

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But let me just actually write the valence electrons.

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So these all have three valence electrons.

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Four, five, six, seven.

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So these all have three electrons in

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its outermost shell.

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It still seems easier for them to give them away than to take

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them, but maybe now, in certain cases, there could be,

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especially in the case of, let's say, boron, there could

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be a situation where it maybe could gain five electrons,

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although that seems hard.

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It's much easier to give away three and that's why a lot of

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the, quote-unquote, official metals

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show up in this category.

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And as you can see, as you go down the periodic table you

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can kind of have metals that have more and

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more valence electrons.

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So for, let's say, lead.

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It's still a metal, even though it has

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four valence electrons.

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And that's because the atom is so big, its radius is so large

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that the outermost shell is so far away from the nucleus,

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that those electrons are easier to take off.

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So for example, as you go down, carbon, those electrons

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are very close to the nucleus.

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So they're very hard to take off.

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So carbon would probably more likely gain electrons from

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somebody else to get to eight.

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While these guys' valence electrons are so far away from

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the nucleus that they're more likely to kind of want to get

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rid of them to get to eight and get back to an electron

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configuration of, let's say, xenon.

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And you go and then these guys are the nonmetals.

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Right?

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They're likely to probably gain

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electrons in most reactions.

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And then this yellow category that I said was highly

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reactive, especially highly reactive with the alkali

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metals over here, these are called halogens.

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And you've probably heard the word before.

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Halogen lamps.

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That's no mistake there to call them halogen lamps.

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That's not a random choice of words.

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Maybe I'll do a video on halogen lamps in the future.

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And then finally, we're at the noble gases.

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What's interesting about the noble gases?

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Well they have eight electrons in their

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outermost shell, right?

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Except for helium.

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Helium has two, right?

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Helium's electron configuration is 1s2.

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But all of these other guys, this guy's electron

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configuration is 1s2.

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This is neon.

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1s2, 2s2, 2p6.

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So he has eight electrons in his outermost shell.

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So he's happy.

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Argon, same thing.

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The outermost shell will look like 3s2, 3p6.

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Krypton will have in its outermost shell

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will be 3s2, 3p6.

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It will also have some 3d electrons around as it

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backfilled back here.

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But all of these have eight in its outermost shell, so

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they're happy.

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They have no incentive to react.

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They're kind of like, hey, all of you other elements, just,

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you know, you guys can do all that crazy reactions that

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you've got to do, but we're happy.

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And we don't want to give or take electrons.

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And because of that these guys are highly, highly unreactive.

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Very, very unreactive.

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And you know, back in the day, when they used to make these

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kind of zeppelins, these big blimps-- the Hindenburg is a

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famous example-- they used hydrogen.

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And obviously hydrogen is a pretty reactive substance.

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It's actually very combustible and that's why it blows up

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very fast. And that's why now, clowns or children's balloon

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manufacturers, they instead would prefer to use helium.

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Because helium is a noble gas and it's very unreactive.

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And it's very unlikely to explode at a

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child's birthday party.

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But anyway, I think I'm done now with this video.

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And in the next video we'll talk a little bit more about

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trends across the periodic table.