Ionic, covalent, and metallic bonds | Chemical bonds | Chemistry | Khan Academy
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Ionic, covalent, and metallic bonds | Chemical bonds | Chemistry | Khan Academy


Everything we’ve been dealing
with so far has just been with the individual atoms,
but atoms bond. Or another way of saying it
is, they stick together. Because if atoms didn’t stick
together, then we’d all be essentially just a collection
of atoms and this video wouldn’t be being produced. So atoms stick together and
they form molecules. You take a bunch of
atoms together and they’ll stick together. And they’ll form molecules. And then obviously molecules
start building up and you get other structures. And if we started talking about
organic chemistry, you’d have a bunch of atoms, a lot of
carbons and hydrogens and other things, fitting
together and they’d be forming proteins. And then proteins would fit
together to form organic structures. And you fit enough of those
together, and you’ll eventually get someone recording
a YouTube video. So this is where
it all starts. Atoms bond. Or they stick together. And the purpose of this video
is to think about the different types of ways
that an atom can stick to another atom. So the first, and kind of the
most powerful way– or I think of it as the most powerful way–
is if you take an atom that really wants to give an
electron, and then you have another atom that really wants
to take an electron. Right? And we’ve talked about
this before. An atom that wants to give an
electron wants to give it because it’s trying to get into
a stable configuration in its outer shell. Everyone wants to look
like a noble gas. They’re all envious of the noble
gases, because the noble gases have eight electrons
in their outer shell. So who wants to give? Well if you look at the period
table, the people who want to give really badly– and we’ve
talked about this a good bit– are the alkali metals. These guys just really want
to offload an electron. And there are other people
who want to give them. But let’s take the
extreme example. So these guys really want
to offload an electron. And who wants to take
an electron? Well, the halogens. We’ve talked about it. These guys love taking
electrons. They’re not the only ones. But they have a very high
electronegativity. They really want to
take electrons. So if you put these around
each other, what happens? Let’s say, sodium
and chlorine. And let’s say we wanted to
flavor some of our food. So you have some sodium and
you have some chlorine. So sodium– let me draw its
valence shell– sodium’s valence shell looks like this. It’s got one electron sitting
there that it would really just like to get rid of. And then chlorine
looks like this. It has seven valence
electrons. One, two, three, four,
five, six, seven. So what happens is this
guy wants to escape. This little blue electron right
here really wants to escape the sodium
and essentially move into the chlorine. And obviously, it’s not
like a one-for-one. You’d have billions and
trillions of these atoms rolling around, and these
electrons jump off, then they go to one, then they
jump to another. But for the sake of our
purposes, let’s say we just have these two atoms. And what
you have is that that electron jumps off. And then if that electron
jumps off, what happens to sodium? Well then the sodium
has no electrons in its valence shell. Although it does. Now its valence shell is one
lower, but we can say it’s lost that one electron
that was out there. And now its atomic configuration
will look a lot like neon. Right? Sodium, you lose an electron,
now it looks a lot like neon, at least its electron
configuration. But now it has one fewer
electrons than protons. So now, it has a positive
charge. It was neutral back here. Right? Now it’s positive. And now, what does a
chlorine look like? And I’m kind of mixing up
notations, but that’s really just to give you the idea. So chlorine before had
seven electrons. One, two, three, four,
five, six, seven. That electron had jumped
onto the chlorine. So now it’s happy. It looks a lot like argon now. It has a completely filled
valence shell. And what’s the charge now? Well in has one more. Now it will have 18 electrons
instead of 17. Right? So what is its charge now? It has 17 protons,
18 electrons. It has a negative one charge. So I’ll just put a negative
up there. It has a negative charge now
because it got that electron from sodium. So now these guys are both
happy from an electron configuration point of view. They both have these stable
valence shells. But they’re attracted to
each other, right? Coulomb forces. Positive is attracted to
negative, negative is attracted to positive. And it can be very strong, this
electrostatic force, so they stick to each other. And so this force
of attraction, this is an ionic bond. So they essentially
will form NaCl. They’re not sharing electrons. This guy wanted the electrons so
badly, and this guy wanted to give them away so badly, he
just handed the electron over. But then he says, oh, by the
way, now that I handed you the electron, you’re negative,
I’m positive. I want to stick to you. And then we formed table
salt and we’re ready to season our food. Now that’s the situation where
one guy really wants to offload an electron, one guy
really wants to take it. What happens in the situation
where they’re both not as extreme in their views in
whether or not they want to give or take electrons? So let’s think of a few
other examples. The best example is
elemental oxygen. Right? Let’s see, elemental oxygen. So this right here
is an ionic bond. Not to jump back and forth,
but I’m not sure if I just mentioned that. Why is it called
an ionic bond? Because we formed ions. When we donated the electron
from sodium to chlorine, we formed an ion. The sodium, this became a
cation, because it’s positive. And this became an anion,
because it’s negative. And then they stuck
to each other, so this is an ionic bond. Fair enough. Now what happens, like I was
just starting to say, if we have two elements that aren’t
that different in how much they want electrons. Their electronegativity
is very similar. And the best example
of that is we had two of the same element. So let’s say I had oxygen. Let’s have one oxygen there. Let’s look at the periodic table
to make sure that we’re not– oxygen has six valence
electrons, right? One, two, three, four, five,
six valence electrons. Right? It’s 2s2, 2p4. So on the second shell
it has six electrons. So oxygen has one, two, three,
four, five, six. And then let’s say we
have another oxygen. It has one, two, three, four,
five, six electrons. Now both of these oxygen
atoms would love to have eight electrons. They’d be stable. They could start pretending
like they’re a noble gas. But clearly, they don’t
have eight electrons. And let’s say in this, all they
have around each other is other oxygen atoms. So what
they can do is say, this oxygen goes to that oxygen, and
says, hey, why don’t we share some electrons and then
we can both pretend that we have eight electrons. And this guy says,
oh, sure enough. So we can just bring
him over here. And I’ll just write
him in blue. Oxygen doesn’t necessarily
have to change colors. I’m joking. So I’m just going to draw this
guy over on this side just so you recognize that this is
different than this guy. And then they share
these electrons. So they share these electrons. And we could do it by
drawing a line here. So they’re sharing two
pairs of electrons. So this guy right here, he had
six electrons, but he can kind of pretend that he has this
electron and that electron. So he has eight in his
valence shell. And this guy, he’s going
to do the same thing. He has one, two, three, four,
five, six, but he also can kind of pretend that
these guys are also in his valence shell. So he’s happy. And this notion, where you’re
actually sharing electrons, where these electrons are going
to go and both electron probability distribution clouds
of both atoms. This is called a covalent bond. And this is typical when
you’re dealing with two elements that aren’t very
different in terms of their electronegativity or their
desire to attract electrons. Now, when we talked about
ionization energy, I think, we talked about when oxygen
and water bond, right? And oxygen– oxygen, we’ve
drawn that– is six. Not oxygen. Water. Oxygen and hydrogen to form
water, and hydrogen looks something like this. Right? You have a hydrogen
atom there. You have a hydrogen
atom there. They said, hey, why don’t
we get together. Let’s share some atoms. And the
hydrogen atoms say, oh, OK, let’s share some atoms.
Let me rewrite this oxygen like this, so it becomes clear
that we’re sharing. So if I rewrite this
oxygen like this. I essentially split up
one of these pairs. And these hydrogens come along
and they share one hydrogen there, one hydrogen there. This guy can pretend like he
has his first shell filled, because you can only
put two there. That’s where the eight
rule breaks down in the first shell. This guy can pretend, too. And now oxygen can pretend like
he’s got eight electrons in his valence shell. And everyone’s happy. So this is also a
covalent bond. Another way we could have
written this, and I think I did this in the last
video, I could have written it like this. Where the implication of this
line, each of these lines involve two electrons. These are equivalent
statements. But in this situation,
oxygen is more electronegative than hydrogen. It wants to get the electrons
more than hydrogen. So in this situation, the
electrons are going to spend more time around oxygen than
they will around hydrogen. So hydrogen will experience, I
guess you could call it, a partial positive charge on this
side of the molecule, while the oxygen side will
experience a partial negative. I’m going to draw it
real small, because it’s a partial negative. This is called a polar
covalent bond. Because it’s still covalent. We’re sharing electrons. But it’s polar, because the
electrons are getting pulled to spend most of their time
at one side of the atom. And since that is the case, the
molecule as a whole, the collection of atoms, is going
to have polarity. One side of the molecule is
going to be more negative than the other side, which will be
more positive because the electrons are spending more
time on that side. Now the last bond we can talk
about, and I’ve touched on this a little bit, is
the metallic bond. I was in a metallic bond in
high school, but anyway, that’s a subject for
another video. But with metals, you can’t
really draw the electron structure there. But what happens with, let’s
say we have iron, right? And you have just a bunch
of neutral iron atoms sitting around. And we established the one
commonality of metals, what makes something metallic or have
metallic characteristics is that they have a bunch of
electrons in their outer orbital that they’re
very giving. They’re very happy to share. So if you put a bunch of these
guys together, what happens is they share their electrons. So they all become positive. They’re very communal
this way. The metallic atoms. And then
their electrons kind of just form this sea out here. But they all share. E minus. E minus. E minus. E minus. And because their electrons are
all on the sea and they’ve kind of gotten this positive
charge, they’re attracted to the sea that they’ve created. They’re attracted to their
shared electron pool that all of the atoms have donated to. And this is essentially what
allows, well definitely, metals to be conductive, because
you have this pool of electrons that are very
easy to move around. And also it’s what makes
them malleable. Because even if you
have visually– it’s a little intuitive. There’s nothing exact here. But you can kind
of move these. You can imagine that this is
kind of a big pudding of electrons or big glue
of electrons. And you can move, you can bend
the rod or flatten the rod without having it break
or get brittle. While if you’re talking about
salts that have a very strong but rigid bond, if you were to
try to bend a bar of salt, the bond will just be broken. There’s no, kind of, squishy
electron mush that you can kind of bend around
and play with. Anyway, so those are
the three bonds. And hopefully that gives
you a little intuition. And this is super useful,
because in the rest of chemistry, everything we do will
essentially involve some combination of these bonds. And we’ll start talking about
what these bonds mean in terms of the temperature at which they
boil, or the properties of the molecules themselves. Anyway, see you in
the next video.

About James Carlton

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100 thoughts on “Ionic, covalent, and metallic bonds | Chemical bonds | Chemistry | Khan Academy

  1. Khan academy has raised my grades from 60% to 70% and some 80% I'm going into grade 11 and this summer, I'll be taking notes on math, English, film, and other classes that I could master from khan academy. you explain it better than any teacher ever could. Praise the lord for Sal Khan, thank you so much for teaching us in a better way and now we can feel less stressed through school, because you have saved us, the students that were close to failing, are passing with 80% or 90% as of right now. Keep up the great work and never give up!

  2. You said the Na will have one less electron and proton after sharing with Cl. But Protons will remain the same no matter what the reaction. Could you care to explain if protons are also shared or remain same ?

  3. If oxygen naturally forms a covalent bond with itself, how do any oxygen atoms end up bonded with anything else but themselves?

  4. i wouldn't mind some advertisements in the videos. You deserve to get rich of these very useful videos (I did donate by the way via khanacademy.org).

  5. How can you tell just by looking at the amount of valence electrons two atoms have to whether or not they would bond covalently or ionicly? I can easily draw a diagram for the sodium where it looks like they are sharing a pair of electrons and vice versa for the covalent bond drawings.

  6. 9:36 “…. and everyone is happy!” Idk why but that made the lil atoms sound cute LOL XD ps dude ur explanation are so clear to me. I kno im a bit of rookie in this particular area but I understand certain patterns in this existence which things must rely and must be relative to one another by bonds and equal balances that may span into different dimensional perspectives creating new unknown to us more complex material !! But seems like a lot of structural, electric energized balances have a key role to get the ball rolling. And like creating new sub dispersed branches and they within them! Well how I see it I atleast lol idk 😅😭🤣 thanks so much man you rock!! Looking forward to more vids ! 👊😎

  7. The interesting case is hydrogen chloride which in certain cases forms an ionic bond tyat is essentially a compond of ionised chlorine coupled with asingle ffree proton!

  8. Thanks for the video !
    Too bad you don't explain that ionic vs covalent is not black and white, that the contribution to the forces are always part ionic and part covalent, depending on the electronegativity difference !

  9. Amazingly Taught! taking summer class for chemistry so kind of preparing myself before I hit the road. 
    Thank you!

  10. Now please explain what a James Bond is.

    Let me guess. Two Oxygen atoms bound to 7…not sure what those are.

  11. omg, I'm glad I found this… my chemistry teacher is a VERY VERY religious person and preaches all the time… it would've been really great to hear if she wasn't a homophobic, sexist, and tends to insult other religions all the time…

  12. It s weird.
    It is repetitive sometime there s subtitles,
    other time there no subtitle on Youtube.
    Does anyone know how to solve on the phone?

  13. it is amazing how many bad teachers exist in the system, I wonder if anyone ever did a study on how poorly people with phd teaches in collages and universities. its shocking. but real

  14. I can't stand your voice and the way you repeat phrases or words like 6 times before completing the sentence. Srry Sal, I like your Math guy's voice tho.

  15. Who could have thought teachings this easy and entertaining way! Sal did! Now so many of others are following his path and making our life easy. Can not thank you enough, khan!

  16. In the first intro i don't understand when i listen and watch i really understand and now i get it how they form. but i need to learn more, also i learn your video more thank you keep it up .^_^

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