Atomic radius trends on periodic table

WEBVTT
Kind: captions
Language: en

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Voiceover: Let's think a little bit about

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the notion of atomic size

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or atomic radius in this video.

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At first thought, you might
think well this might be

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a fairly straight-forward thing.

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If I'm trying to calculate the radius of

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some type of circular object

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I'm just thinking about
well what's the distance

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between the center of that circular object

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and the edge of it.

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So the length of this
line right over here.

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That would be the radius.

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And so a lot of people
when they conceptualize

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an atom they imagine a positive nucleus

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with the protons in the
center right over here

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then they imagine the
electrons on these fixed orbits

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around that nucleus

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so they might imagine some electrons

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in this orbit right over here,

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just kind of orbiting around

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and then there might be a few more

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on this orbit out here orbiting around,

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orbiting around out here.

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And you might say, "well okay,
that's easy to figure out

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the atomic radius.

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I just figure out the distance

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between the nucleus and
the outermost electron

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and we could call that the radius."

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That would work except for the fact

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that this is not the
right way to conceptualize

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how electrons or how they move

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or how they are distributed
around a nucleus.

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Electrons are not in
orbits the way that planets

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are in orbit around the sun

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and we've talked about
this in previous videos.

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They are in orbitals

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which are really just
probability distributions

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of where the electrons can be,

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but they're not that well defined.

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So, you might have an orbital,

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and I'm just showing you in 2 dimensions.

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It would actually be in 3 dimensions,

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where maybe there's a high probability

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that the electrons where I'm
drawing it in kind of this

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more shaded in green.

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But there's some probability
that the electrons

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are in this area right over here

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and some probability that the electrons

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are in this area over here,

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and let's say even a lower
probability that the electrons

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are over this, like this over here.

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And so you might say,

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well at a moment the electron's there.

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The outermost electron we'd say is there.

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You might say well that's the radius.

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But in the next moment,

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there's some probability
it might be likely

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that it ends up here.

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But there's some probability

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that it's going to be over there.

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Then the radius could be there.

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So electrons, these orbitals,

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these diffuse probability distributions,

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they don't have a hard edge,

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so how can you say

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what the size of an atom actually is?

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There's several techniques
for thinking about this.

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One technique for thinking about this

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is saying, okay, if you
have 2 of the same atom,

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that are- 2 atoms of the same element

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that are not connected to each other,

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that are not bonded to each other,

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that are not part of the same molecule,

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and you were able to determine somehow

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the closest that you could
get them to each other

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without them bonding.

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So, you would kind of see,

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what's the closest that they can,

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they can kind of get to each other?

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So let's say that's one of them

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and then this is the
other one right over here.

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And if you could figure out that distance,

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that closest, that minimum distance,

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without some type of, you know,

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really, I guess, strong
influence happening here,

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but just the minimum
distance that you might see

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between these 2 and then
you could take half of that.

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So that's one notion.

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That's actually called
the Van der Waals radius.

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Another way is well what
about if you have 2 atoms,

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2 atoms of the same element

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that are bonded to each other?

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They're bonded to each other
through a covalent bond.

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So a covalent bond, we've already-

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we've seen this in the past.

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The most famous of covalent bonds is well,

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a covalent bond you
essentially have 2 atoms.

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So that's the nucleus of one.

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That's the nucleus of the other.

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And they're sharing electrons.

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So their electron clouds actually,

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their electron clouds actually
overlap with each other,

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actually overlap with each other

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so the covalent bond,

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there the electrons in that bond

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could spend some of
their time on this atom

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and some of their time on
this atom right over here.

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And so when you have a
covalent bond like this,

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you can then find the distance

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between the 2 nuclei

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and take half of that and call that

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call that the atomic radius.

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So these are all different
ways of thinking about it.

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Now, with that out of the way,

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let's think about what
the trends for atomic size

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or atomic radii would be
in the periodic table.

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So the first thing to think about is

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what do you think will be
the trend for atomic radii

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as we move through a period.

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So let's say we're in the fourth period

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and we were to go from
potassium to krypton.

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What do you think is going
to be the trend here?

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And if you want to think
about the extremes,

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how do you think potassium
is going to compare

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to krypton in terms of atomic radius.

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I encourage you to pause this video

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and think about that on your own.

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Well, when you're in the fourth period,

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the outermost electrons

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are going to be in your fourth shell.

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Here, you're filling out 4S1, 4S2.

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Then you start back filling
into the 3D subshell

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and then you start filling
again in 4P1 and so forth.

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You start filling out the P subshell.

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So as you go from potassium to krypton,

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you're filling out that
outermost fourth shell.

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Now what's going on there?

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Well, when you're at potassium,

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you have 19- 1, 2, 3, 4,
5, 6, 7, 8, 9, 10, 11, 12,

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13, 14, 15, 16, 17, 18, 19.

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You have 19 protons

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and you have 19 electrons.

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Well I'll just draw those.

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1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,

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12, 13, 14, 15, 16, 17, 18,

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but you only have 1
electron in that outermost,

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in that fourth shell, so let's
just say that's that electron

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at a moment, just for visually.

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It doesn't necessarily have to be there

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but just to visualize that.

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So that 1 electron right over there,

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you have 19, yeah, you have 19 protons.

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So, you have some, I guess you could say

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Coulom force that is attracting it,

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that is keeping it there.

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But if you go to krypton,

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all of a sudden you have
much more positive charge

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in the nucleus.

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So you have 1, 2, 3, 4, 5, 6, 7, 8-

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I don't have to do them all.

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You have 36.

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You have a positive charge of 36.

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Let me write that, you have plus 36.

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Here you have plus 19.

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And you have 36 electrons,

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you have 36 electrons-

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I don't know, I've lost track of it,

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but in your outermost shell,

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in your fourth, you're
going to have the 2S

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and then you're going to have the 6P.

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So you have 8 in your outermost shell.

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So that'd be 1, 2, 3, 4, 5, 6, 7, 8.

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So one way to think about it,

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if you have more positive
charge in the center,

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and you have more negative
charge on that outer shell,

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so that's going to bring
that outer shell inward.

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It's going to have more

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I guess you could imagine one way,

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more Coulomb attraction right over there.

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And because of that,

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that outer most shell
is going to drawn in.

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Krypton is going to be smaller,

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is going to have a smaller
atomic radius than potassium.

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So the trend, as you go to the right

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is that you are getting,

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and the general trend I would say,

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is that you are getting smaller

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as you go to the right in a period.

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That's the reason why
the smallest atom of all,

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the element with the smallest atom

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is not hydrogen, it's helium.

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Helium is actually smaller than hydrogen,

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depending on how you,

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depending on what technique
you use to measure it.

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That's because, if we
take the simplest case,

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hydrogen, you have 1 proton in the nucleus

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and then you have 1
electron in that 1S shell,

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and in helium you have 2,

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2 protons in the nucleus

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and I'm not drawing the neutrons

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and obviously there's different isotopes,

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different numbers of neutrons,

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but you have 2 electrons now
in your outer most shell.

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So you have more, I guess you could say,

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you could have more
Coulomb attraction here.

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This is plus 2 and then these
2 combined are negative 2.

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They're going to be drawn inward.

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So, that's the trend
as we go to the right,

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as we go from the left to the right

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of the periodic table,
we're getting smaller.

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Now what do you think is going to happen

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as we go down the period table?

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As we go down the periodic
table in a given group?

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Well, as we go down a group,

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each new element down the group,

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we're adding, we're in a new period.

00:08:38.914 --> 00:08:40.211
We're adding a new shell.

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So you're adding more
and more and more shells.

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Here you have just the first shell,

00:08:43.173 --> 00:08:44.660
now the second shell and each shell

00:08:44.660 --> 00:08:46.903
is getting further and
further and further away.

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So as you go down the periodic table,

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you are getting, you are getting larger.

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You're having a larger atomic radius

00:08:54.746 --> 00:08:57.212
depending on how you are measuring it.

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So what's the general trend?

00:08:58.833 --> 00:09:00.606
Well if you get larger as you go down,

00:09:00.606 --> 00:09:03.453
that means you're getting
smaller as you go up.

00:09:03.453 --> 00:09:10.562
You get smaller, smaller as you go up.

00:09:10.562 --> 00:09:12.922
So, what are going to be,

00:09:12.922 --> 00:09:15.177
what's going to be the smallest ones?

00:09:15.177 --> 00:09:17.469
Well, we've already said
helium is the smallest.

00:09:17.469 --> 00:09:19.603
So what are going to
be some of the largest?

00:09:19.603 --> 00:09:21.306
What are going to be some
of the largest atoms?

00:09:21.306 --> 00:09:22.723
Well that's going to be the atoms

00:09:22.723 --> 00:09:24.305
down here at the bottom left.

00:09:24.305 --> 00:09:25.371
So, these are going to be large,

00:09:25.371 --> 00:09:26.754
these are going to be small.

00:09:26.754 --> 00:09:31.141
So, large over here, small over here

00:09:31.141 --> 00:09:32.010
and the general trend,

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as you go from the bottom
left to the top right

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you are getting, you are getting smaller.


Electronegativity

WEBVTT
Kind: captions
Language: en

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Voiceover: What I want to
talk about in this video

00:00:01.929 --> 00:00:05.717
are the notions of Electronegativity,

00:00:05.717 --> 00:00:13.071
electro, negati, negativity,

00:00:13.071 --> 00:00:15.692
and a closely, and a closely related

00:00:15.692 --> 00:00:22.003
idea of Electron Affinity,
electron affinity.

00:00:22.003 --> 00:00:24.405
And they're so closely
related that in general,

00:00:24.405 --> 00:00:27.328
if something has a high electronegativity,

00:00:27.328 --> 00:00:29.719
they have a high electron affinity,

00:00:29.719 --> 00:00:31.228
but what does this mean?

00:00:31.228 --> 00:00:34.351
Well, electron affinity
is how much does that atom

00:00:34.351 --> 00:00:37.705
attract electrons, how much
does it like electrons?

00:00:37.705 --> 00:00:41.667
Does it want, does it
maybe want more electrons?

00:00:41.667 --> 00:00:45.283
Electronegativity is a
little bit more specific.

00:00:45.283 --> 00:00:49.085
It's when that atom is
part of a covalent bond,

00:00:49.085 --> 00:00:53.333
when it is sharing
electrons with another atom,

00:00:53.333 --> 00:00:55.891
how likely is it or how badly does it want

00:00:55.891 --> 00:00:58.873
to hog the electrons
in that covalent bond?

00:00:58.873 --> 00:01:01.844
Now what do I mean by hogging electrons?

00:01:01.844 --> 00:01:03.820
So let me make, let me write this down.

00:01:03.820 --> 00:01:13.871
So how badly wants to hog,

00:01:13.871 --> 00:01:15.815
and this is an informal
definition clearly,

00:01:15.815 --> 00:01:18.803
hog electrons, keep the electrons,

00:01:18.803 --> 00:01:20.973
to spend more of their time closer to them

00:01:20.973 --> 00:01:23.572
then to the other party
in the covalent bond.

00:01:23.572 --> 00:01:28.258
And this is how, how
much they like electrons,

00:01:28.258 --> 00:01:32.732
or how much affinity they
have towards electrons.

00:01:32.732 --> 00:01:39.674
So how much they want electrons.

00:01:39.674 --> 00:01:41.043
And you can see that these are very,

00:01:41.043 --> 00:01:43.569
these are very related notions.

00:01:43.569 --> 00:01:45.510
This is within the context
of a covalent bond,

00:01:45.510 --> 00:01:47.732
how much electron affinity is there?

00:01:47.732 --> 00:01:50.104
Well this, you can think of it
as a slightly broader notion,

00:01:50.104 --> 00:01:54.052
but these two trends go absolutely
in line with each other.

00:01:54.052 --> 00:01:55.883
And to think about, to just think about

00:01:55.883 --> 00:01:58.075
electronegativity makes it
a little bit more tangible.

00:01:58.075 --> 00:01:59.833
Let's think about one of the most famous

00:01:59.833 --> 00:02:00.855
sets of covalent bonds,

00:02:00.855 --> 00:02:03.292
and that's what you see
in a water molecule.

00:02:03.292 --> 00:02:07.983
Water, as you probably know, is H two O,

00:02:07.983 --> 00:02:11.166
you have an oxygen atom,

00:02:11.166 --> 00:02:13.934
and you have two hydrogens.

00:02:13.934 --> 00:02:17.074
Each of the hydrogen's
have one valence electron,

00:02:17.074 --> 00:02:21.095
and the oxygen has, we see
here, at it's outermost shell,

00:02:21.095 --> 00:02:25.596
it has one, two, three, four,
five, six valence electrons.

00:02:25.596 --> 00:02:31.184
One, two, three, four,
five, six valence electrons.

00:02:31.184 --> 00:02:33.106
And so you can imagine,
hydrogen would be happy

00:02:33.106 --> 00:02:35.398
if it was able to somehow
pretend like it had another

00:02:35.398 --> 00:02:37.788
electron then it would have
an electron configuration

00:02:37.788 --> 00:02:41.218
a stable, first shell that
only requires two electrons,

00:02:41.218 --> 00:02:42.621
the rest of them require eight,

00:02:42.621 --> 00:02:45.214
hydrogen would feel, hey
I'm stable like helium

00:02:45.214 --> 00:02:46.787
if it could get another electron.

00:02:46.787 --> 00:02:49.288
And oxygen would feel,
hey I'm stable like neon

00:02:49.288 --> 00:02:51.159
if I could get two more electrons.

00:02:51.159 --> 00:02:53.759
And so what happens is they
share each other's electrons.

00:02:53.759 --> 00:02:57.642
This, this electron can
be shared in conjunction

00:02:57.642 --> 00:02:59.206
with this electron for this hydrogen.

00:02:59.206 --> 00:03:01.800
So that hydrogen can kind
of feel like it's using

00:03:01.800 --> 00:03:03.125
both and it gets more stable,

00:03:03.125 --> 00:03:04.676
it stabilizes the outer shell,

00:03:04.676 --> 00:03:06.301
or it stabilizes the hydrogen.

00:03:06.301 --> 00:03:08.027
And likewise, that electron could be,

00:03:08.027 --> 00:03:10.494
can be shared with the hydrogen,

00:03:10.494 --> 00:03:13.027
and the hydrogen can kind
of feel more like helium.

00:03:13.027 --> 00:03:14.465
And then this oxygen can feel like

00:03:14.465 --> 00:03:16.487
it's a quid pro quo,

00:03:16.487 --> 00:03:18.467
it's getting something in
exchange for something else.

00:03:18.467 --> 00:03:20.236
It's getting the electron, an electron,

00:03:20.236 --> 00:03:22.856
it's sharing an electron
from each of these hydrogens,

00:03:22.856 --> 00:03:26.646
and so it can feel like
it's, that it stabilizes it,

00:03:26.646 --> 00:03:30.261
similar to a, similar to a neon.

00:03:30.261 --> 00:03:32.447
But when you have these covalent bonds,

00:03:32.447 --> 00:03:34.193
only in the case where they are equally

00:03:34.193 --> 00:03:35.882
electronegative would you have a case

00:03:35.882 --> 00:03:37.203
where maybe they're sharing,

00:03:37.203 --> 00:03:38.482
and even there what happens

00:03:38.482 --> 00:03:40.361
in the rest of the molecule might matter,

00:03:40.361 --> 00:03:42.323
but when you have something like this,

00:03:42.323 --> 00:03:43.507
where you have oxygen and hydrogen,

00:03:43.507 --> 00:03:45.515
they don't have the
same electronegativity.

00:03:45.515 --> 00:03:49.756
Oxygen likes to hog electrons
more than hydrogen does.

00:03:49.756 --> 00:03:51.416
And so these electrons are not gonna spend

00:03:51.416 --> 00:03:52.617
an even amount of time.

00:03:52.617 --> 00:03:54.639
Here I did it kind of just drawing these,

00:03:54.639 --> 00:03:57.941
you know, these valence
electrons as these dots.

00:03:57.941 --> 00:03:59.490
But as we know, the electrons are in this

00:03:59.490 --> 00:04:03.575
kind of blur around, around the,

00:04:03.575 --> 00:04:06.665
around the actual nuclei,

00:04:06.665 --> 00:04:09.507
around the atoms that make up the atoms.

00:04:09.507 --> 00:04:11.971
And so, in this type of a covalent bond,

00:04:11.971 --> 00:04:15.459
the electrons, the two electrons
that this bond represents,

00:04:15.459 --> 00:04:18.316
are going to spend more
time around the oxygen

00:04:18.316 --> 00:04:20.829
then they are going to
spend around the hydrogen.

00:04:20.829 --> 00:04:23.564
And these, these two
electrons are gonna spend

00:04:23.564 --> 00:04:25.144
more time around the oxygen,

00:04:25.144 --> 00:04:27.425
then are going to spend
around the hydrogen.

00:04:27.425 --> 00:04:30.360
And we know that because
oxygen is more electronegative,

00:04:30.360 --> 00:04:31.773
and we'll talk about
the trends in a second.

00:04:31.773 --> 00:04:34.656
This is a really important
idea in chemistry,

00:04:34.656 --> 00:04:36.915
and especially later on as
you study organic chemistry.

00:04:36.915 --> 00:04:39.091
Because, because we know that

00:04:39.091 --> 00:04:40.407
oxygen is more electronegative,

00:04:40.407 --> 00:04:41.761
and the electrons spend more time

00:04:41.761 --> 00:04:44.377
around oxygen then around hydrogen,

00:04:44.377 --> 00:04:47.135
it creates a partial
negative charge on this side,

00:04:47.135 --> 00:04:50.517
and partial positive charges
on this side right over here,

00:04:50.517 --> 00:04:55.712
which is why water has many of
the properties that it does,

00:04:55.712 --> 00:04:59.292
and we go into much more in
depth in that in other videos.

00:04:59.292 --> 00:05:00.984
And also when you study organic chemistry,

00:05:00.984 --> 00:05:02.830
a lot of the likely reactions that are

00:05:02.830 --> 00:05:04.745
going to happen can be predicted,

00:05:04.745 --> 00:05:06.525
or a lot of the likely molecules that form

00:05:06.525 --> 00:05:09.833
can be predicted based
on elecronegativity.

00:05:09.833 --> 00:05:10.872
And especially when you start going

00:05:10.872 --> 00:05:12.404
into oxidation numbers
and things like that,

00:05:12.404 --> 00:05:15.436
electronegativity will tell you a lot.

00:05:15.436 --> 00:05:19.037
So now that we know what
electronegativity is,

00:05:19.037 --> 00:05:21.435
let's think a little bit about what is,

00:05:21.435 --> 00:05:24.062
as we go through, as we start,

00:05:24.062 --> 00:05:27.880
as we go through, as
we go through a period,

00:05:27.880 --> 00:05:29.687
as say as we start in group one,

00:05:29.687 --> 00:05:35.177
and we go to group, and
as we go all the way

00:05:35.177 --> 00:05:38.464
all the way to, let's say the halogens,

00:05:38.464 --> 00:05:42.700
all the way up to the yellow
column right over here,

00:05:42.700 --> 00:05:44.131
what do you think is going to be

00:05:44.131 --> 00:05:47.848
the trend for electronegativity?

00:05:47.848 --> 00:05:49.232
And once again, one way to think about it

00:05:49.232 --> 00:05:50.629
is to think about the extremes.

00:05:50.629 --> 00:05:53.965
Think about sodium, and
think about chlorine,

00:05:53.965 --> 00:05:54.935
and I encourage you to pause

00:05:54.935 --> 00:05:56.930
the video and think about that.

00:05:56.930 --> 00:05:58.624
Assuming you've had a go at it,

00:05:58.624 --> 00:06:01.293
and it's in some ways the same idea,

00:06:01.293 --> 00:06:03.537
or it's a similar idea
as ionization energy.

00:06:03.537 --> 00:06:06.451
Something like sodium
has only one electron

00:06:06.451 --> 00:06:07.785
in it's outer most shell.

00:06:07.785 --> 00:06:09.855
It'd be hard for it to
complete that shell,

00:06:09.855 --> 00:06:12.036
and so to get to a stable
state it's much easier

00:06:12.036 --> 00:06:15.706
for it to give away that
one electron that it has,

00:06:15.706 --> 00:06:18.688
so it can get to a stable
configuration like neon.

00:06:18.688 --> 00:06:22.625
So this one really wants
to give away an electron.

00:06:22.625 --> 00:06:24.668
And we saw in the video
on ionization energy,

00:06:24.668 --> 00:06:26.783
that's why this has a
low ionization energy,

00:06:26.783 --> 00:06:29.590
it doesn't take much
energy, in a gaseous state,

00:06:29.590 --> 00:06:32.196
to remove an electron from sodium.

00:06:32.196 --> 00:06:33.620
But chlorine is the opposite.

00:06:33.620 --> 00:06:35.708
It's only one away from
completing it's shell.

00:06:35.708 --> 00:06:37.580
The last thing it wants to
do is give away electron,

00:06:37.580 --> 00:06:40.682
it wants an electron really,
really, really, really badly

00:06:40.682 --> 00:06:42.937
so it can get to a configuration of argon,

00:06:42.937 --> 00:06:45.984
so it can complete its third shell.

00:06:45.984 --> 00:06:49.118
So the logic here is
that sodium wouldn't mind

00:06:49.118 --> 00:06:50.578
giving away an electron,

00:06:50.578 --> 00:06:52.880
while chlorine really
would love an electron.

00:06:52.880 --> 00:06:55.471
So chlorine is more
likely to hog electrons,

00:06:55.471 --> 00:06:59.727
while sodium is very
unlikely to hog electrons.

00:06:59.727 --> 00:07:00.953
So this trend right here,

00:07:00.953 --> 00:07:02.505
when you go from the left to the right,

00:07:02.505 --> 00:07:04.815
your electronegativity, let me write this,

00:07:04.815 --> 00:07:07.089
your getting more electronegative.

00:07:07.089 --> 00:07:13.811
More electro, electronegative, as you,

00:07:13.811 --> 00:07:16.623
as you go to the right.

00:07:16.623 --> 00:07:18.237
Now what do you think
the trend is going to be

00:07:18.237 --> 00:07:22.403
as you go down, as you go down in a group?

00:07:22.403 --> 00:07:25.774
What do you think the trend
is going to be as you go down?

00:07:25.774 --> 00:07:27.250
Well I'll give you a hint.

00:07:27.250 --> 00:07:31.246
Think about, think about
atomic radii, and given that,

00:07:31.246 --> 00:07:31.973
pause the video and think about

00:07:31.973 --> 00:07:32.896
what do you think the trend is?

00:07:32.896 --> 00:07:34.747
Are we gonna get more
or less electronegative

00:07:34.747 --> 00:07:36.871
as we move down?

00:07:36.871 --> 00:07:39.267
So once again I'm assuming
you've given a go at it,

00:07:39.267 --> 00:07:41.810
so as we know, from the
video on atomic radii,

00:07:41.810 --> 00:07:44.093
our atom is getting larger,
and larger, and larger,

00:07:44.093 --> 00:07:46.191
as we add more and more and more shells.

00:07:46.191 --> 00:07:50.838
And so cesium has one electron
in it's outer most shell,

00:07:50.838 --> 00:07:52.150
in the sixth shell,

00:07:52.150 --> 00:07:55.854
while, say, lithium has one electron.

00:07:55.854 --> 00:07:57.620
Everything here, all
the group one elements,

00:07:57.620 --> 00:07:59.471
have one electron in
it's outer most shell,

00:07:59.471 --> 00:08:01.746
but that fifty fifth electron,

00:08:01.746 --> 00:08:03.282
that one electron in the
outer most shell in cesium,

00:08:03.282 --> 00:08:05.810
is a lot further away then
the outer most electron

00:08:05.810 --> 00:08:08.334
in lithium or in hydrogen.

00:08:08.334 --> 00:08:12.156
And so because of that, it's, well one,

00:08:12.156 --> 00:08:14.460
there's more interference
between that electron and the

00:08:14.460 --> 00:08:16.792
nucleus from all the other
electrons in between them,

00:08:16.792 --> 00:08:18.403
and also it's just further away,

00:08:18.403 --> 00:08:20.513
so it's easier to kind of grab it off.

00:08:20.513 --> 00:08:24.780
So cesium is very likely to give up,

00:08:24.780 --> 00:08:27.698
it's very likely to give up electrons.

00:08:27.698 --> 00:08:30.752
It's much more likely to give
up electrons than hydrogen.

00:08:30.752 --> 00:08:33.159
So, as you go down a given group,

00:08:33.159 --> 00:08:39.045
you're becoming less, less
electronegative, electronegative.

00:08:39.045 --> 00:08:41.115
So what, what are, based on this,

00:08:41.115 --> 00:08:44.586
what are going to be
the most electronegative

00:08:44.586 --> 00:08:46.016
of all the atoms?

00:08:46.016 --> 00:08:47.467
Well they're going to be the ones

00:08:47.467 --> 00:08:50.447
that are in the top and the
right of the periodic table,

00:08:50.447 --> 00:08:52.478
they're going to be these right over here.

00:08:52.478 --> 00:08:54.634
These are going to be
the most electronegative,

00:08:54.634 --> 00:08:56.837
Sometimes we don't think as
much about the noble gases

00:08:56.837 --> 00:08:59.092
because they aren't, they
aren't really that reactive,

00:08:59.092 --> 00:09:01.133
they don't even form covalent bond,

00:09:01.133 --> 00:09:02.597
because they're just happy.

00:09:02.597 --> 00:09:03.896
While these characters up here,

00:09:03.896 --> 00:09:06.119
they sometimes will form covalent bonds,

00:09:06.119 --> 00:09:09.855
and when they do, they really
like to hog those electrons.

00:09:09.855 --> 00:09:11.524
Now what are the least electronegative,

00:09:11.524 --> 00:09:13.620
sometimes called very electropositive?

00:09:13.620 --> 00:09:15.570
Well these things down
here in the bottom left.

00:09:15.570 --> 00:09:18.328
These, over here, they have only,

00:09:18.328 --> 00:09:19.569
you know in the case of cesium,

00:09:19.569 --> 00:09:21.835
they have one electron to give away

00:09:21.835 --> 00:09:25.333
that would take them to a
stable state like, like xenon,

00:09:25.333 --> 00:09:27.510
or in the case of these group two elements

00:09:27.510 --> 00:09:28.525
they might have to give away two,

00:09:28.525 --> 00:09:29.547
but it's much easier to give away two

00:09:29.547 --> 00:09:31.813
then to gain a whole bunch of them.

00:09:31.813 --> 00:09:34.145
And they're big, they're big atoms.

00:09:34.145 --> 00:09:35.925
So those outer most electrons are getting

00:09:35.925 --> 00:09:39.448
less attracted to the positive nucleus.

00:09:39.448 --> 00:09:40.718
So the trend in the periodic table

00:09:40.718 --> 00:09:42.562
as you go from the bottom left,

00:09:42.562 --> 00:09:44.787
to the top right,

00:09:44.787 --> 00:09:48.787
you're getting more, more
electro, electronegative.


Metallic nature

WEBVTT
Kind: captions
Language: en

00:00:00.728 --> 00:00:01.789
Voiceover: What I want to do in this video

00:00:01.789 --> 00:00:04.439
is discuss what it means to be a metal,

00:00:04.439 --> 00:00:06.946
or metallic in nature.

00:00:06.946 --> 00:00:09.336
First, let's just think about the metals

00:00:09.336 --> 00:00:10.794
that we encounter in everyday life,

00:00:10.794 --> 00:00:12.247
or based on our experience
the things that we

00:00:12.247 --> 00:00:14.625
associate with being a metal.

00:00:14.625 --> 00:00:17.004
The elements that really
jump out at us as metals

00:00:17.004 --> 00:00:18.649
or we always refer to,
"Hey, that's a metal,

00:00:18.649 --> 00:00:23.421
"or that's metallic,"
are things like iron,

00:00:23.421 --> 00:00:31.699
or nickel, or copper, or silver, or gold,

00:00:31.699 --> 00:00:32.786
or aluminum, or at least for me,

00:00:32.786 --> 00:00:34.374
these are the ones that
immediately pop out.

00:00:34.374 --> 00:00:37.062
I've seen these things before,

00:00:37.062 --> 00:00:40.035
and they all feel like metals to me,

00:00:40.035 --> 00:00:43.158
but also think about what's
true about these things

00:00:43.158 --> 00:00:44.418
and as we'll see many other elements

00:00:44.418 --> 00:00:46.615
on the periodic table that give them

00:00:46.615 --> 00:00:47.660
this metallic nature.

00:00:47.660 --> 00:00:50.705
What do we associate with
having a metallic nature?

00:00:50.705 --> 00:00:53.842
One is that these things can be shiny.

00:00:53.842 --> 00:00:56.199
These things tend to be shiny.

00:00:56.199 --> 00:00:59.336
There's kind of a gloss
when light shines on it.

00:00:59.336 --> 00:01:00.691
They're not just kind of a matte color.

00:01:00.691 --> 00:01:02.942
They look metallic literally.

00:01:02.942 --> 00:01:04.296
That's sometimes a word
that's used for it.

00:01:04.296 --> 00:01:06.866
It has a metallic shininess to it.

00:01:06.866 --> 00:01:08.163
Another thing that we associate with it

00:01:08.163 --> 00:01:11.120
is that they tend to be fairly dense.

00:01:11.120 --> 00:01:13.168
If I take a metal, a block of a metal

00:01:13.168 --> 00:01:14.322
and if I drop it into water,

00:01:14.322 --> 00:01:16.519
I imagine that sinking, not floating

00:01:16.519 --> 00:01:18.283
on top of the water.

00:01:18.283 --> 00:01:20.617
We also imagine them having a very high

00:01:20.617 --> 00:01:23.003
melting point, that they tend to be solid

00:01:23.003 --> 00:01:24.512
at room temperature.

00:01:24.512 --> 00:01:28.937
Solid at room temperature.

00:01:28.937 --> 00:01:31.388
As we'll see, this is true of all metals

00:01:31.388 --> 00:01:34.322
except for one of them which is mercury

00:01:34.322 --> 00:01:36.447
which is shiny but at room temperature

00:01:36.447 --> 00:01:41.249
as you might be familiar
is in its liquid form.

00:01:41.249 --> 00:01:43.061
Now the other things that
I associate with a metal

00:01:43.061 --> 00:01:44.657
is that I can make things out of them.

00:01:44.657 --> 00:01:47.886
I can bend them and shape
them in different ways.

00:01:47.886 --> 00:01:48.933
I think of aluminum foil.

00:01:48.933 --> 00:01:49.652
I can bend it.

00:01:49.652 --> 00:01:51.536
It's not just going to crack.

00:01:51.536 --> 00:01:54.265
I can bend it and put it
into different shapes.

00:01:54.265 --> 00:01:56.229
Even things like iron it might take

00:01:56.229 --> 00:01:57.831
a lot of pressure to do it,

00:01:57.831 --> 00:01:59.959
but they're bendable, they're malleable,

00:01:59.959 --> 00:02:02.654
and definitely things like
gold and silver and copper

00:02:02.654 --> 00:02:05.550
you can actually mold into
different types of jewelry.

00:02:05.550 --> 00:02:07.169
If you put pressure on it,

00:02:07.169 --> 00:02:09.380
it's more likely to bend than crack

00:02:09.380 --> 00:02:10.971
and just kind of shear off.

00:02:10.971 --> 00:02:15.463
So let's put malleability.
They're malleable.

00:02:16.162 --> 00:02:18.025
The other thing I associate with metals

00:02:18.025 --> 00:02:20.270
is that they conduct electricity well.

00:02:20.270 --> 00:02:24.027
Conduct electricity.

00:02:24.027 --> 00:02:26.244
A place that you'll see metal in your life

00:02:26.244 --> 00:02:27.640
is if you open up your electronics

00:02:27.640 --> 00:02:29.897
you'll see wires that might
be made out of copper,

00:02:29.897 --> 00:02:31.168
or you might have components that are made

00:02:31.168 --> 00:02:33.538
out of other metals like gold, or silver,

00:02:33.538 --> 00:02:35.689
or whatever else.

00:02:35.689 --> 00:02:38.506
Given that these are
some of the properties

00:02:38.506 --> 00:02:40.068
that we associate with metals,

00:02:40.068 --> 00:02:41.171
let's think about what's happening

00:02:41.171 --> 00:02:45.060
at the atomic level to give these elements

00:02:45.060 --> 00:02:47.531
these properties.

00:02:47.531 --> 00:02:48.816
The way I think about it let's just

00:02:48.816 --> 00:02:50.460
go with copper for a second.

00:02:50.460 --> 00:02:52.669
Let's just imagine a block of copper

00:02:52.669 --> 00:02:55.426
at the atomic level.

00:02:55.426 --> 00:02:57.030
Let's say this is one copper nucleus

00:02:57.030 --> 00:02:58.572
right over there,

00:02:58.572 --> 00:03:01.326
and it has its sea of electrons.

00:03:01.326 --> 00:03:05.135
It has its sea of electrons,

00:03:05.135 --> 00:03:06.380
or not its sea of electrons.

00:03:06.380 --> 00:03:08.673
It has all of its electrons
in their various orbitals.

00:03:08.673 --> 00:03:10.903
We'll talk about sea of
electrons in a second,

00:03:10.903 --> 00:03:12.951
but this is kind of its cloud of electrons

00:03:12.951 --> 00:03:14.056
I should say.

00:03:14.056 --> 00:03:15.747
So this is electron cloud.

00:03:15.747 --> 00:03:18.014
The electrons are just
jumping around in this cloud.

00:03:18.014 --> 00:03:20.493
It's really a probability density,

00:03:20.493 --> 00:03:22.141
or there's kind of a certain probability

00:03:22.141 --> 00:03:24.695
that could be at any point in that cloud.

00:03:24.695 --> 00:03:27.946
Let's imagine a big solid piece of copper.

00:03:27.946 --> 00:03:30.540
You would have a bunch of these.

00:03:30.540 --> 00:03:34.632
You would have a bunch
of these all together,

00:03:34.632 --> 00:03:37.820
all forming the solid.

00:03:37.820 --> 00:03:41.343
What allows metals to be malleable,

00:03:41.343 --> 00:03:44.980
to do things like conduct electricity

00:03:44.980 --> 00:03:47.259
which is the movement of electrons,

00:03:47.259 --> 00:03:50.208
is essentially that they're very willing

00:03:50.208 --> 00:03:52.127
to share electrons with each other.

00:03:52.127 --> 00:03:54.568
By sharing electrons, so you can imagine

00:03:54.568 --> 00:03:56.247
this is one copper atom
and that's another,

00:03:56.247 --> 00:03:58.297
let's say they're sharing some electrons,

00:03:58.297 --> 00:03:59.753
that's what allows the electricity

00:03:59.753 --> 00:04:01.825
or this flow of electrons to happen.

00:04:01.825 --> 00:04:04.417
If these electrons are loosely bound,

00:04:04.417 --> 00:04:06.922
then if you put a potential
difference of voltage,

00:04:06.922 --> 00:04:09.208
let's say that you put
a potential difference

00:04:09.208 --> 00:04:11.165
so that this side is more negative,

00:04:11.165 --> 00:04:13.193
and then this side is more positive,

00:04:13.193 --> 00:04:14.292
then the electrons are going to want

00:04:14.292 --> 00:04:15.773
to get away from the negative charge,

00:04:15.773 --> 00:04:18.019
and move towards the positive charge.

00:04:18.019 --> 00:04:19.892
If they're relatively freely bound,

00:04:19.892 --> 00:04:23.179
they can kind of move from one cloud

00:04:23.179 --> 00:04:24.204
to the next.

00:04:24.204 --> 00:04:26.035
You kind of end up having
what's often called

00:04:26.035 --> 00:04:27.880
a sea of electrons.

00:04:27.880 --> 00:04:29.413
Let me write that down.

00:04:29.413 --> 00:04:36.668
You have a sea of
electrons which would make

00:04:36.668 --> 00:04:37.992
this conductive and that's why you see

00:04:37.992 --> 00:04:40.941
so much wire made out of copper.

00:04:40.941 --> 00:04:42.470
The sea of electrons is also what

00:04:42.470 --> 00:04:44.077
makes it malleable.

00:04:44.077 --> 00:04:46.908
If someone on this side were to put

00:04:46.908 --> 00:04:47.889
a lot of pressure this way,

00:04:47.889 --> 00:04:50.306
and on that side put a
lot of pressure that way,

00:04:50.306 --> 00:04:52.789
things that are rigid
would just kind of crack

00:04:52.789 --> 00:04:56.220
and break, right, would
just break right over there,

00:04:56.220 --> 00:04:58.384
but because you have the sea of electrons

00:04:58.384 --> 00:04:59.573
it allows it to be malleable.

00:04:59.573 --> 00:05:01.512
This part might just
bend down a little bit,

00:05:01.512 --> 00:05:03.171
that part might bend up,

00:05:03.171 --> 00:05:05.183
but they're not going
to, the metallic bond

00:05:05.183 --> 00:05:07.137
is not going to break.

00:05:07.137 --> 00:05:08.932
Given that this metallic nature

00:05:08.932 --> 00:05:10.708
really comes from the willingness

00:05:10.708 --> 00:05:14.654
of these atoms to share
electrons with each other,

00:05:14.654 --> 00:05:16.590
to create the sea of electrons,

00:05:16.590 --> 00:05:18.756
I encourage you to pause this video

00:05:18.756 --> 00:05:22.465
and think about which atoms
on the periodic table,

00:05:22.465 --> 00:05:24.536
or which elements are
more likely to do that,

00:05:24.536 --> 00:05:27.747
to share electrons with
others and with each other.

00:05:27.747 --> 00:05:29.187
Really, this is the same principle

00:05:29.187 --> 00:05:31.199
that we thought about ionization energy,

00:05:31.199 --> 00:05:33.819
and electronegativity.

00:05:33.819 --> 00:05:36.259
So pause the video.

00:05:36.259 --> 00:05:39.661
I'm assuming you've had a go at it.

00:05:39.661 --> 00:05:42.939
So which elements are most likely

00:05:42.939 --> 00:05:44.718
to share electrons?

00:05:44.718 --> 00:05:47.268
We've already seen that
if we're on the left side

00:05:47.268 --> 00:05:48.895
of the periodic table of elements,

00:05:48.895 --> 00:05:50.660
Group One for example,

00:05:50.660 --> 00:05:53.365
they only have one valence electron.

00:05:53.365 --> 00:05:54.519
It would be very hard for them

00:05:54.519 --> 00:05:58.080
to get enough electrons to
complete that outer shell.

00:05:58.080 --> 00:06:00.097
If they get rid of that
one valence electron,

00:06:00.097 --> 00:06:02.826
they can go to a more stable state.

00:06:02.826 --> 00:06:05.744
They really want to give away electrons,

00:06:05.744 --> 00:06:07.634
and the ones over here, they're so close

00:06:07.634 --> 00:06:10.035
if we talk about the halogens,

00:06:10.035 --> 00:06:11.763
they're one electron away from completing

00:06:11.763 --> 00:06:12.844
their outer shell.

00:06:12.844 --> 00:06:14.617
They're greedy. They want
to hog these electrons.

00:06:14.617 --> 00:06:16.084
They tend to be electronegative.

00:06:16.084 --> 00:06:17.803
The noble gases, they're done.

00:06:17.803 --> 00:06:19.508
They definitely don't
want to share electrons

00:06:19.508 --> 00:06:20.222
with anyone.

00:06:20.222 --> 00:06:22.965
They're kind of in a very stable state.

00:06:22.965 --> 00:06:24.429
Now, the other thing
that we've talked about

00:06:24.429 --> 00:06:27.219
is as we go down a group,

00:06:27.219 --> 00:06:30.752
our atoms are getting larger,
and larger, and larger.

00:06:30.752 --> 00:06:33.226
So the outermost, that 55th electron

00:06:33.226 --> 00:06:35.950
in cesium is much more loosely bound

00:06:35.950 --> 00:06:38.637
because it's further away than say

00:06:38.637 --> 00:06:40.615
the third electron in lithium.

00:06:40.615 --> 00:06:42.312
So just as we saw as the elements

00:06:42.312 --> 00:06:46.090
in this bottom left have a
very low ionization energy.

00:06:46.090 --> 00:06:48.647
It doesn't take much energy to remove

00:06:48.647 --> 00:06:50.486
an electron from them,

00:06:50.486 --> 00:06:52.219
these are the ones that are most likely

00:06:52.219 --> 00:06:53.037
to share electrons,

00:06:53.037 --> 00:06:55.920
and these actually have the
highest metallic nature.

00:06:55.920 --> 00:07:05.112
So high metallic, high metallic nature.

00:07:05.112 --> 00:07:07.847
The ones on the top right,

00:07:07.847 --> 00:07:09.740
these are going to be the opposite.

00:07:09.740 --> 00:07:12.143
They're very unlikely to share electrons.

00:07:12.143 --> 00:07:14.058
They're very electronegative.

00:07:14.058 --> 00:07:16.558
They have a very high ionization energy.

00:07:16.558 --> 00:07:20.457
They have a low metallic nature.

00:07:20.457 --> 00:07:22.088
I could imagine some things are popping

00:07:22.088 --> 00:07:23.697
into your brain at this point.

00:07:23.697 --> 00:07:26.516
We started thinking of the elements

00:07:26.516 --> 00:07:30.784
that in our everyday life
we associate with metals,

00:07:30.784 --> 00:07:32.372
but what I'm saying is
that these things over

00:07:32.372 --> 00:07:34.330
have an even higher metallic nature,

00:07:34.330 --> 00:07:35.676
but what about something like calcium.

00:07:35.676 --> 00:07:37.940
Every day what I imagined
when I typically,

00:07:37.940 --> 00:07:39.834
or when a lot of people imagine calcium,

00:07:39.834 --> 00:07:41.406
they think of kind of a chalky,

00:07:41.406 --> 00:07:43.957
a white chalky substance, very rigid,

00:07:43.957 --> 00:07:46.364
not very malleable, not very good,

00:07:46.364 --> 00:07:47.831
not very shiny, not very good

00:07:47.831 --> 00:07:48.879
at conducting electricity.

00:07:48.879 --> 00:07:50.266
Based on what I just told you,

00:07:50.266 --> 00:07:52.220
this would have a higher metallic nature

00:07:52.220 --> 00:07:54.379
than something like aluminum.

00:07:54.379 --> 00:07:55.181
What you have to remind yourself

00:07:55.181 --> 00:07:57.738
is that what you see is
not actually pure calcium,

00:07:57.738 --> 00:07:59.356
that kind of chalky thing.

00:07:59.356 --> 00:08:01.024
That's calcium carbonate.

00:08:01.024 --> 00:08:02.758
Pure calcium, actually, this is actually

00:08:02.758 --> 00:08:04.798
a picture of pure calcium.

00:08:04.798 --> 00:08:09.287
It is shiny. It does have
these metallic properties.

00:08:09.287 --> 00:08:11.889
The general trend here
is that all of these,

00:08:11.889 --> 00:08:13.926
these are very high in metallic nature,

00:08:13.926 --> 00:08:15.491
and these are very low metallic nature

00:08:15.491 --> 00:08:16.759
which also makes you probably realize

00:08:16.759 --> 00:08:19.151
while most of the periodic table

00:08:19.151 --> 00:08:20.993
is a metal of some form.

00:08:20.993 --> 00:08:22.778
If aluminum is a metal,

00:08:22.778 --> 00:08:24.748
and all of these things have a higher,

00:08:24.748 --> 00:08:27.780
have a higher metallic nature
than all of this stuff,

00:08:27.780 --> 00:08:29.484
all of this stuff are metals,

00:08:29.484 --> 00:08:30.516
and that is the case.

00:08:30.516 --> 00:08:32.026
The S block, the D block, the F block,

00:08:34.655 --> 00:08:36.397
these are all metals.

00:08:36.397 --> 00:08:39.475
Then a good chunk of the P block,

00:08:39.475 --> 00:08:41.157
a good chunk of the P block

00:08:41.157 --> 00:08:43.816
are considered metals,
and then these are kind of

00:08:43.816 --> 00:08:46.661
sometimes referred to as metalloids,

00:08:46.661 --> 00:08:50.333
Only this section of the periodic table

00:08:50.333 --> 00:08:51.885
is not considered a metal.

00:08:51.885 --> 00:08:52.599
That makes sense.

00:08:52.599 --> 00:08:53.803
Nobel gases, they are gases.

00:08:53.803 --> 00:08:55.104
They don't, they're not very reactive.

00:08:55.104 --> 00:08:57.240
they don't bond so they don't form

00:08:57.240 --> 00:08:58.783
kind of a structure that can even do

00:08:58.783 --> 00:09:00.155
this type of thing.

00:09:00.155 --> 00:09:02.344
These other ones over here even carbon

00:09:02.344 --> 00:09:05.168
when it is formed a lattice,

00:09:05.168 --> 00:09:07.908
it does not conduct electricity well.

00:09:07.908 --> 00:09:11.260
It tends to not be so malleable

00:09:11.260 --> 00:09:12.987
if you think about
something like a diamond,

00:09:12.987 --> 00:09:14.785
or if you think about, well, a diamond

00:09:14.785 --> 00:09:16.648
might be the best example of that.

00:09:16.648 --> 00:09:18.352
Anyway, hopefully this gives you a sense

00:09:18.352 --> 00:09:21.205
of metallic nature and the trends

00:09:21.205 --> 00:09:22.255
in the periodic table.

00:09:22.255 --> 00:09:25.171
High metallic nature, and
as you go to the top right,

00:09:25.171 --> 23:59:59.999
lower and lower metallic nature.


ATP hydrolysis mechanism

WEBVTT
Kind: captions
Language: en

00:00:00.367 --> 00:00:05.366
Sal: In the previous video we
talked about how an ATP molecule

00:00:05.366 --> 00:00:09.900
can, in the presence of water,
hydrolysis will take place,

00:00:09.900 --> 00:00:12.833
and one of the phosphoryl
groups could be plunked off,

00:00:12.833 --> 00:00:15.567
and how that would release
energy because these electrons

00:00:15.567 --> 00:00:18.269
are going to be able to go
into a lower energy state.

00:00:21.160 --> 00:00:24.634
You could imagine that this
was already not that stable

00:00:24.634 --> 00:00:28.233
of a bond, that all these
negative charges wanted to get

00:00:28.233 --> 00:00:30.766
away from each other, and
once this is plunked off,

00:00:30.766 --> 00:00:32.300
then of course when they get into a more

00:00:32.300 --> 00:00:34.766
comfortable state energy is released.

00:00:34.766 --> 00:00:37.100
But you might say, "I want
more. I want to actually see

00:00:37.100 --> 00:00:41.863
"the mechanism by which the
hydrolysis takes place."

00:00:41.863 --> 00:00:44.367
That's what I'm going to do in this video.

00:00:44.367 --> 00:00:46.833
Let's start with our ATP molecule,

00:00:46.833 --> 00:00:50.867
and let's throw some water in there, H2O.

00:00:50.900 --> 00:00:53.801
Let's say this is water right here,

00:00:53.833 --> 00:00:56.033
oxygen with two hydrogens.

00:00:56.033 --> 00:00:59.366
I'll do the two pairs
of oxygen that aren't in

00:00:59.366 --> 00:01:04.100
bonds right over here,
in the outermost shell.

00:01:04.100 --> 00:01:08.469
Actually let me draw one more
water molecule right over here.

00:01:08.469 --> 00:01:09.701
There's multiple way that you could

00:01:09.701 --> 00:01:13.200
actually depict this right over here.

00:01:13.384 --> 00:01:16.402
Let's say that one of these,

00:01:16.402 --> 00:01:18.300
let's say this water molecule right here,

00:01:18.300 --> 00:01:22.967
and obviously no chemical
reaction happens this cleanly.

00:01:22.967 --> 00:01:24.500
This is showing how it
could happen if they just

00:01:24.500 --> 00:01:27.100
bump into each other
in the exact right way.

00:01:27.100 --> 00:01:29.766
This has got this pair of electrons.

00:01:29.766 --> 00:01:31.966
Let's say this pair of
electrons is essentially

00:01:31.966 --> 00:01:35.700
given by this oxygen to
this hydrogen proton.

00:01:35.700 --> 00:01:38.700
We could draw it like this right there.

00:01:38.700 --> 00:01:42.433
It nabs just the hydrogen, then
both of these electrons that

00:01:42.433 --> 00:01:45.966
are in this pair, that are
in this bond I should say,

00:01:45.966 --> 00:01:50.833
go back to the oxygen to form,
essentially you could think

00:01:50.833 --> 00:01:53.900
of this as a pair of electrons
attached to that oxygen.

00:01:53.900 --> 00:01:58.367
Then that gives the oxygen
license to allow these

00:01:58.367 --> 00:02:04.167
two electrons to form a
bond with the phosphorous.

00:02:04.167 --> 00:02:07.233
The phosphorous isn't in
the mood to form six bonds,

00:02:07.233 --> 00:02:09.115
it's already got five, and this is

00:02:09.115 --> 00:02:11.100
a fairly uncomfortable situation for it.

00:02:11.100 --> 00:02:15.034
That allows these two electrons
right over here to go,

00:02:15.034 --> 00:02:19.866
these two electrons to go to
this oxygen, just like that.

00:02:19.900 --> 00:02:24.634
As a result of everything
I've just depicted

00:02:24.634 --> 00:02:27.366
happening, what does it look like?

00:02:27.366 --> 00:02:29.499
Let me draw a little arrow here.

00:02:29.499 --> 00:02:34.100
Now you're going to have
your adenosine diphosphate.

00:02:34.100 --> 00:02:35.961
Let me put it over here.

00:02:35.961 --> 00:02:40.192
And just to be clear,
this thing has now gained,

00:02:40.853 --> 00:02:43.100
this oxygen right over here,
one way you can think about it,

00:02:43.100 --> 00:02:47.033
it was party to a bond so it
was sharing two electrons.

00:02:47.033 --> 00:02:49.766
Now it's getting both of the electrons,

00:02:49.766 --> 00:02:52.567
so now it's going to
have a negative charge.

00:02:52.567 --> 00:02:55.700
It had half of-- Actually it
had a little bit more than half,

00:02:55.700 --> 00:02:59.366
it's more electronegative
than the phosphorous.

00:02:59.366 --> 00:03:02.767
Now it's going to get both of them.

00:03:02.767 --> 00:03:05.166
Now this is going to
have a negative charge.

00:03:05.166 --> 00:03:08.033
This is the adenosine diphosphate.

00:03:08.033 --> 00:03:12.033
This phosphoryl group over
here, let me just redraw it.

00:03:13.201 --> 00:03:15.033
It's going to look like this.

00:03:15.033 --> 00:03:17.366
Double bond to that oxygen.

00:03:17.366 --> 00:03:22.433
You have this oxygen right
over here. That's there.

00:03:22.433 --> 00:03:24.700
You have that oxygen right over there.

00:03:24.700 --> 00:03:28.766
And of course the water, the
water molecule, or I guess

00:03:28.766 --> 00:03:33.166
now it's just going to be
an OH group, is going to be,

00:03:33.166 --> 00:03:37.701
it has ... Let me see if I can
make the colors interesting.

00:03:37.701 --> 00:03:41.966
These two electrons have now
formed a bond and you have

00:03:41.966 --> 00:03:46.834
the oxygen and of course
this hydrogen here.

00:03:46.834 --> 00:03:49.033
I haven't draw in any other oxygens but

00:03:49.033 --> 00:03:51.767
this thing still has two lone pairs.

00:03:51.767 --> 00:03:54.566
And of course you have this character

00:03:54.566 --> 00:03:58.766
right over here, who gained a proton.

00:04:00.073 --> 00:04:02.033
This one you can depict like this.

00:04:02.033 --> 00:04:05.500
It's oxygen, hydrogen, hydrogen.

00:04:05.500 --> 00:04:07.900
It had one lone pair, but now it gave half

00:04:07.900 --> 00:04:11.233
of this lone pair to form
a bond with that hydrogen,

00:04:11.233 --> 00:04:14.300
and hydrogen without an
electron is just a proton.

00:04:14.300 --> 00:04:17.300
Actually let me draw it like
this just so you can see it.

00:04:17.300 --> 00:04:21.300
These two are now the
two electrons in this

00:04:21.300 --> 00:04:28.633
bond with this, with this hydrogen proton.

00:04:28.633 --> 00:04:31.433
This right over here, this
is a positively charged,

00:04:31.433 --> 00:04:35.766
this is a positively charged
molecule right over here.

00:04:35.766 --> 00:04:38.100
And you can imagine
maybe this thing breaks

00:04:38.100 --> 00:04:39.900
off and it could be viewed as a proton,

00:04:39.900 --> 00:04:42.966
or you could view this as a
positive charged molecule,

00:04:42.966 --> 00:04:46.033
but either way this is the
reaction that we just depicted.

00:04:46.033 --> 00:04:50.566
You have ATP being,
hydrolysis takes place.

00:04:50.566 --> 00:04:55.100
You're left with ADP, you're
left with a phosphate,

00:04:55.100 --> 00:04:57.767
a released phosphate molecule,

00:04:57.767 --> 00:04:59.833
and then you're left
with a positive charge.

00:04:59.833 --> 00:05:01.500
You could either view this
as kind of a proton or the

00:05:01.500 --> 00:05:07.501
proton attaches and forms a
hydronium ion right over here.

00:05:07.501 --> 00:05:10.367
And of course in the process
of doing all of this,

00:05:10.367 --> 00:05:14.700
as these electrons got
into a more comfortable

00:05:14.700 --> 00:05:17.300
situation just sitting
right over here and allowing

00:05:17.300 --> 00:05:23.133
this thing to break
off, it releases energy.

00:05:23.376 --> 00:05:29.300
It releases, it releases energy,
which is in most biological

00:05:29.300 --> 00:05:34.201
systems the whole point of
having the ATP molecules around.


ATP: Adenosine triphosphate

WEBVTT
Kind: captions
Language: en

00:00:00.566 --> 00:00:06.433
Sal: ATP or adenosine triposphate
is often referred to as

00:00:06.433 --> 00:00:11.567
the currency of energy, or
the energy store, adenosine,

00:00:11.567 --> 00:00:16.233
the energy store in biological systems.

00:00:16.233 --> 00:00:18.900
What I want to do in this video is get

00:00:18.900 --> 00:00:21.966
a better appreciation of why that is.

00:00:21.966 --> 00:00:24.633
Adenosine triposphate.

00:00:24.633 --> 00:00:28.833
At first this seems like
a fairly complicated term,

00:00:28.833 --> 00:00:31.300
adenosine triphosphate, and
even when we look at its

00:00:31.300 --> 00:00:34.434
molecular structure it seems
quite involved, but if we break

00:00:34.434 --> 00:00:36.634
it down into its constituent
parts it becomes a little bit

00:00:36.634 --> 00:00:40.566
more understandable and we'll
begin to appreciate why,

00:00:40.566 --> 00:00:45.000
how it is a store of energy
in biological systems.

00:00:45.033 --> 00:00:47.900
The first part is to break
down this molecule between

00:00:47.900 --> 00:00:49.767
the part that is adenosine
and the part that

00:00:49.767 --> 00:00:53.366
is the triphosphates, or
the three phosphoryl groups.

00:00:54.304 --> 00:00:57.033
The adenosine is this
part of the molecule,

00:00:57.033 --> 00:00:59.167
let me do it in that same color.

00:00:59.167 --> 00:01:02.966
This part right over here is adenosine,

00:01:02.966 --> 00:01:06.233
and it's an adenine connected to a ribose

00:01:06.233 --> 00:01:10.500
right over there, that's
the adenosine part.

00:01:10.500 --> 00:01:12.833
And then you have three phosphoryl groups,

00:01:12.833 --> 00:01:16.166
and when they break off they
can turn into a phosphate.

00:01:17.704 --> 00:01:22.500
The triphosphate part
you have, triphosphate,

00:01:22.500 --> 00:01:27.767
you have one phosphoryl
group, two phosphoryl groups,

00:01:27.767 --> 00:01:32.233
two phosphoryl groups and
three phosphoryl groups.

00:01:32.233 --> 00:01:35.966
One way that you can conceptualize
this molecule which will

00:01:35.966 --> 00:01:39.233
make it a little bit easier
to understand how it's a store

00:01:39.233 --> 00:01:44.366
of energy in biological systems
is to represent this whole

00:01:44.366 --> 00:01:47.967
adenosine group, let's just
represent that as an A.

00:01:47.967 --> 00:01:50.100
Actually let's make that an Ad.

00:01:50.100 --> 00:01:51.900
Then let's just show it bonded to

00:01:51.900 --> 00:01:54.300
the three phosphoryl groups.

00:01:55.883 --> 00:01:59.033
I'll make those with a P
and a circle around it.

00:01:59.033 --> 00:02:02.166
You can do it like that,
or sometimes you'll see it

00:02:02.166 --> 00:02:04.100
actually depicted, instead
of just drawing these

00:02:04.100 --> 00:02:07.100
straight horizontal lines
you'll see it depicted

00:02:07.100 --> 00:02:09.766
with essentially higher energy bonds.

00:02:09.766 --> 00:02:12.900
You'll see something like that to show

00:02:12.900 --> 00:02:15.367
that these bonds have a lot of energy.

00:02:15.367 --> 00:02:22.700
But I'll just do it this way
for the sake of this video.

00:02:22.700 --> 00:02:25.500
These are high energy bonds.

00:02:25.500 --> 00:02:26.833
What does that mean, what does that

00:02:26.833 --> 00:02:29.833
mean that these are high energy bonds?

00:02:29.833 --> 00:02:33.100
It means that the electrons
in this bond are in a

00:02:33.100 --> 00:02:36.700
high energy state, and if
somehow this bond could be

00:02:36.700 --> 00:02:39.633
broken these electrons are
going to go into a more

00:02:39.633 --> 00:02:42.834
comfortable state, into
a lower energy state.

00:02:42.834 --> 00:02:45.500
As they go from a higher
energy state into a lower, more

00:02:45.500 --> 00:02:49.166
comfortable energy state they
are going to release energy.

00:02:49.166 --> 00:02:52.433
One way to think about it
is if I'm in a plane and

00:02:52.433 --> 00:02:55.233
I'm about to jump out I'm
at a high energy state,

00:02:55.233 --> 00:02:56.700
I have a high potential energy.

00:02:56.700 --> 00:02:57.967
I just have to do a
little thing and I'm going

00:02:57.967 --> 00:03:00.633
to fall through, I'm going to fall down,

00:03:00.633 --> 00:03:03.566
and as I fall down I can release energy.

00:03:03.566 --> 00:03:06.500
There will be friction
with the air, or eventually

00:03:06.500 --> 00:03:10.766
when I hit the ground
that will release energy.

00:03:10.766 --> 00:03:13.101
I can compress a spring
or I can move a turbine,

00:03:13.101 --> 00:03:14.501
or who knows what I can do.

00:03:14.501 --> 00:03:16.233
But then when I'm sitting on my couch

00:03:16.233 --> 00:03:18.367
I'm in a low energy, I'm comfortable.

00:03:18.367 --> 00:03:23.966
It's not obvious how I could
go to a lower energy state.

00:03:23.966 --> 00:03:26.166
I guess I could fall asleep
or something like that.

00:03:26.166 --> 00:03:29.167
These metaphors break down at some point.

00:03:29.167 --> 00:03:31.900
That's one way to think
about what's going on here.

00:03:31.900 --> 00:03:35.501
The electrons in this bond,
if you can give them just

00:03:35.501 --> 00:03:39.301
the right circumstances they
can come out of that bond

00:03:39.301 --> 00:03:43.301
and go into a lower energy
state and release energy.

00:03:44.146 --> 00:03:46.166
One way to think about it, you start

00:03:46.166 --> 00:03:50.834
with ATP, adenosine triphosphate.

00:03:51.371 --> 00:03:56.833
And one possibility, you put
it in the presence of water and

00:03:56.833 --> 00:04:00.033
then hydrolysis will take
place, and what you're going to

00:04:00.033 --> 00:04:03.766
end up with is one of these things
are going to be essentially,

00:04:03.766 --> 00:04:05.967
one of these phosphoryl
groups are going to be

00:04:05.967 --> 00:04:10.700
popped off and turn into
a phosphate molecule.

00:04:10.700 --> 00:04:14.966
You're going to have
adenosine, since you don't

00:04:14.966 --> 00:04:16.633
have three phosphoryl
groups anymore, you're only

00:04:16.633 --> 00:04:18.966
going to have two phosphoryl
groups, you're going to

00:04:18.966 --> 00:04:24.233
have adenosine diphosphate,
often known as ADP.

00:04:24.233 --> 00:04:25.166
Let me write this down.

00:04:25.166 --> 00:04:29.741
This is ATP, this is ATP right over here.

00:04:29.741 --> 00:04:34.966
And this right over
here is ADP, di for two,

00:04:34.966 --> 00:04:38.700
two phosphoryl groups,
adenosine diphosphate.

00:04:38.700 --> 00:04:43.034
Then this one got plucked
off, this one gets plucked

00:04:43.034 --> 00:04:49.367
off or it pops off and it's
now bonded to the oxygen

00:04:49.367 --> 00:04:53.073
and one of the hydrogens
from the water molecule.

00:04:53.473 --> 00:04:56.366
Then you can have another hydrogen proton.

00:04:56.366 --> 00:04:59.433
The really important part of
this I have not drawn yet,

00:04:59.433 --> 00:05:01.100
the really important part of it,

00:05:01.100 --> 00:05:07.366
as the electrons in this
bond right over here go into

00:05:07.366 --> 00:05:12.033
a lower energy state they
are going to release energy.

00:05:12.033 --> 00:05:16.233
So plus, plus energy.

00:05:16.233 --> 00:05:18.767
Here, this side of the reaction,

00:05:18.767 --> 00:05:23.566
energy released, energy released.

00:05:24.581 --> 00:05:26.300
And this side of the interaction

00:05:26.300 --> 00:05:29.900
you see energy, energy stored.

00:05:29.900 --> 00:05:32.366
As you study biochemistry
you will see time and time

00:05:32.366 --> 00:05:37.233
again energy being used in
order to go from ADP and

00:05:37.233 --> 00:05:40.300
a phosphate to ATP, so
that stores the energy.

00:05:40.300 --> 00:05:41.966
You'll see that in things
like photosynthesis

00:05:41.966 --> 00:05:44.166
where you use light energy to essentially,

00:05:44.166 --> 00:05:47.900
eventually get to a point
where this P is put back on,

00:05:47.900 --> 00:05:52.367
using energy putting this P
back on to the ADP to get ATP.

00:05:52.367 --> 00:05:57.233
Then you'll see when biological
systems need to use energy

00:05:57.233 --> 00:06:01.300
that they'll use the ATP
and essentially hydrolysis

00:06:01.300 --> 00:06:03.234
will take place and they'll
release that energy.

00:06:03.234 --> 00:06:05.701
Sometimes that energy could
be used just to generate heat,

00:06:05.701 --> 00:06:08.234
and sometimes it can be
used to actually forward

00:06:08.234 --> 00:06:12.366
some other reaction or
change the confirmation of

00:06:12.366 --> 00:06:17.829
a protein somehow,
whatever might be the case.


Sn1 reactions introduction

WEBVTT
Kind: captions
Language: en

00:00:00.967 --> 00:00:02.545
Voiceover: So what do we have right here?

00:00:02.545 --> 00:00:05.907
Well this is just a water molecule.

00:00:05.907 --> 00:00:07.335
And this right over here, let's see,

00:00:07.335 --> 00:00:11.846
we have 1, 2, 3 carbons in our backbone

00:00:11.846 --> 00:00:15.431
so this would be meth eth propane.

00:00:15.431 --> 00:00:16.887
We all have single bonds right here,

00:00:16.887 --> 00:00:18.672
so this is propane.

00:00:18.672 --> 00:00:19.932
Let me write that out.

00:00:19.932 --> 00:00:23.973
This is, give myself some space, propane.

00:00:23.973 --> 00:00:25.671
And then on the number 2 carbon,

00:00:25.671 --> 00:00:28.570
I have both a methyl
group and a bromo group

00:00:28.570 --> 00:00:31.732
and bromo comes before
methyl in alphabetical order.

00:00:31.732 --> 00:00:34.938
So I could write this as 2 bromo,

00:00:34.938 --> 00:00:38.441
2 bromo, 2 methyl,

00:00:38.441 --> 00:00:45.519
2 methyl, methyl propane.

00:00:45.519 --> 00:00:48.051
So that's this molecule that
we have right over here.

00:00:48.051 --> 00:00:49.250
Now what we're going to imagine,

00:00:49.250 --> 00:00:50.444
it's sitting in some water

00:00:50.444 --> 00:00:53.320
and I have 1 water molecule
drawn right over here.

00:00:53.320 --> 00:00:56.339
Let's imagine that we have
this bromine right over here.

00:00:56.339 --> 00:00:57.649
It's pretty neutral.

00:00:57.649 --> 00:00:58.667
And it's neutral because it has-

00:00:58.667 --> 00:01:02.049
or it is neutral because
it has 7 valence electrons.

00:01:02.049 --> 00:01:04.685
1, 2, or you could say- or
it has the charge equivalent

00:01:04.685 --> 00:01:06.701
as 1, 2, 3, 4, 5, 6.

00:01:06.701 --> 00:01:08.599
And then it has half of this bond

00:01:08.599 --> 00:01:10.685
that's composed of 2 electrons.

00:01:10.685 --> 00:01:14.301
So that's what's keeping
this neutral right over here.

00:01:14.301 --> 00:01:16.574
But we do know that bromine,

00:01:16.574 --> 00:01:20.172
well you know, it's not
completely unstable.

00:01:20.172 --> 00:01:22.458
If it were to take an electron,

00:01:22.458 --> 00:01:24.552
because that would get it
to 8 valence electrons,

00:01:24.552 --> 00:01:26.963
we know that it's more
electro-negative than carbon

00:01:26.963 --> 00:01:28.487
which means that if it's sharing a bond,

00:01:28.487 --> 00:01:32.576
it's more likely to take the
entire bond than carbon is.

00:01:32.576 --> 00:01:34.602
So let's imagine a scenario.

00:01:34.602 --> 00:01:36.952
Let's imagine a scenario where bromine

00:01:36.952 --> 00:01:41.058
takes these 2 carbons in
this bond right over here.

00:01:41.058 --> 00:01:43.984
And this isn't going to be a
super fast thing that happens

00:01:43.984 --> 00:01:45.710
because this molecule right over here,

00:01:45.710 --> 00:01:47.454
the 2 bromo 2 methyl propane

00:01:47.454 --> 00:01:48.823
is actually reasonably stable,

00:01:48.823 --> 00:01:50.028
so I'm not saying that this is

00:01:50.028 --> 00:01:51.123
going to just happen automatically.

00:01:51.123 --> 00:01:52.498
It's going to happen super fast,

00:01:52.498 --> 00:01:53.997
but it could happen.

00:01:53.997 --> 00:01:56.022
And so to show that this isn't going to be

00:01:56.022 --> 00:01:58.098
you know, only one-way reaction,

00:01:58.098 --> 00:02:00.067
I'll show that it's an equilibrium.

00:02:00.067 --> 00:02:03.410
So the equilibrium, I'll
draw 2 arrows like that.

00:02:03.410 --> 00:02:06.390
So, once this happens, the bromine

00:02:06.390 --> 00:02:08.495
would turn into a bromide anion.

00:02:08.495 --> 00:02:10.564
So let me draw that right over here.

00:02:10.564 --> 00:02:12.506
So the bromide anion.

00:02:12.506 --> 00:02:16.466
So it's going to have 1, 2, 3, 4, 5, 6,

00:02:16.466 --> 00:02:19.611
and then both electrons
from that shared bond.

00:02:19.611 --> 00:02:22.692
Both electrons from that shared bond.

00:02:22.692 --> 00:02:26.972
It now has a negative 1 charge.

00:02:26.972 --> 00:02:28.114
Now if that happened,

00:02:28.114 --> 00:02:30.452
what would happen to this leftover,

00:02:30.452 --> 00:02:32.198
to I guess what's now going to be

00:02:32.198 --> 00:02:35.649
the thing that bromine

00:02:35.649 --> 00:02:37.659
was connected to I guess you could say.

00:02:37.659 --> 00:02:39.200
Let's draw that.

00:02:39.200 --> 00:02:42.857
So we have this carbon,
our number 2 carbon.

00:02:42.857 --> 00:02:45.890
We have CH3 right over there.

00:02:45.890 --> 00:02:49.153
Then we go back to a CH3

00:02:49.153 --> 00:02:51.586
and then we had this blue methyl group.

00:02:51.586 --> 00:02:53.815
So, I'll add this blue
methyl group right over here

00:02:53.815 --> 00:02:54.871
and the way I'm drawing it,

00:02:54.871 --> 00:02:57.187
it kind of pops out of the page.

00:02:57.187 --> 00:03:00.178
My best attempt to draw it
popping out of the page.

00:03:00.178 --> 00:03:05.034
So this is it popping out of the page.

00:03:05.034 --> 00:03:07.784
And now, what's its charge going to be?

00:03:07.784 --> 00:03:10.041
Well it just gave up half of this bond,

00:03:10.041 --> 00:03:12.890
the equivalent of an electron's charge.

00:03:12.890 --> 00:03:15.071
So it just gave up, you
can kind of think of it,

00:03:15.071 --> 00:03:16.641
as giving up an electron,

00:03:16.641 --> 00:03:19.840
so this is going to
have a positive charge.

00:03:19.840 --> 00:03:22.880
This is going to have a positive charge.

00:03:22.880 --> 00:03:25.137
A positive charged carbon like this,

00:03:25.137 --> 00:03:27.658
we would call this a carbocation.

00:03:27.658 --> 00:03:34.405
So this right over here is a
carbocation, positive charge.

00:03:34.405 --> 00:03:37.939
And the reason why this is
not a crazy thing to happen

00:03:37.939 --> 00:03:39.842
is that this is a tertiary carbon,

00:03:39.842 --> 00:03:42.126
which means that it is
connected to 3 other carbons.

00:03:42.126 --> 00:03:43.612
1, 2, 3.

00:03:43.612 --> 00:03:45.777
A tertiary carbon, one
way to think about it,

00:03:45.777 --> 00:03:49.646
is that this positive
charge can kind of be shared

00:03:49.646 --> 00:03:51.764
with its brothers a little bit more.

00:03:51.764 --> 00:03:55.025
So tertiary, a tertiary
carbocation is more stable

00:03:55.025 --> 00:03:56.435
than a secondary and definitely

00:03:56.435 --> 00:03:57.942
more stable than a primary.

00:03:57.942 --> 00:03:58.796
A secondary would be

00:03:58.796 --> 00:04:00.284
if it was only connected to 2 carbons,

00:04:00.284 --> 00:04:02.245
but this is tertiary so
let me write this down.

00:04:02.245 --> 00:04:04.983
This is a tertiary carbocation.

00:04:04.983 --> 00:04:08.618
This carbon is connected
to 3 other carbons.

00:04:08.618 --> 00:04:10.631
That's where the tertiary comes from.

00:04:10.631 --> 00:04:12.918
So once again, it can happen.

00:04:12.918 --> 00:04:14.164
I'm not saying that this reaction's

00:04:14.164 --> 00:04:16.043
just going to go super
fast in that direction.

00:04:16.043 --> 00:04:18.345
That's why we did these equilibriums.

00:04:18.345 --> 00:04:20.917
These equilibrium arrows.

00:04:20.917 --> 00:04:23.494
Now let's bring this oxygen into play.

00:04:23.494 --> 00:04:26.481
So let's bring- now let's bring-

00:04:26.481 --> 00:04:30.595
sorry not the oxygen, let's
bring this water into play.

00:04:30.595 --> 00:04:33.476
So this water, as you can
imagine, the water's neutral

00:04:33.476 --> 00:04:36.794
and it seems pretty
reasonable in this state,

00:04:36.794 --> 00:04:41.051
but the oxygen end of the water does have

00:04:41.051 --> 00:04:42.800
a partial negative charge.

00:04:42.800 --> 00:04:44.411
We've seen in the past.

00:04:44.411 --> 00:04:47.944
We've seen in the past that

00:04:47.944 --> 00:04:49.057
because oxygen is

00:04:49.057 --> 00:04:51.072
a lot more electronegative
than the hydrogens,

00:04:51.072 --> 00:04:52.561
that you have a partial negative side

00:04:52.561 --> 00:04:54.242
on the side of the oxygens

00:04:54.242 --> 00:04:56.445
and you have a partial positive charge

00:04:56.445 --> 00:04:59.820
on the side of the hydrogens.

00:04:59.820 --> 00:05:01.683
On the side of the hydrogens.

00:05:01.683 --> 00:05:04.044
And so you have this positive carbocation.

00:05:04.044 --> 00:05:05.847
This has a partially negative charge.

00:05:05.847 --> 00:05:08.565
So you can imagine that this molecule

00:05:08.565 --> 00:05:11.995
might be attracted to this nucleus.

00:05:11.995 --> 00:05:13.748
Now it's not going to be super attracted

00:05:13.748 --> 00:05:15.811
the way that an hydroxide anion would.

00:05:15.811 --> 00:05:18.232
A hydroxide anion has
a full negative charge.

00:05:18.232 --> 00:05:20.189
This only has a little
partial negative charge.

00:05:20.189 --> 00:05:21.720
But it could still be
attracted to something

00:05:21.720 --> 00:05:23.676
very positive like this.

00:05:23.676 --> 00:05:26.344
So in this situation, the water molecule

00:05:26.344 --> 00:05:28.876
is a weak nucleophile.

00:05:28.876 --> 00:05:32.038
So this is a weak nucleophile.

00:05:32.038 --> 00:05:34.686
Not as strong as a hydroxide anion

00:05:34.686 --> 00:05:35.900
that has a full negative charge,

00:05:35.900 --> 00:05:37.528
but if it sees something
positive like this

00:05:37.528 --> 00:05:39.111
and it bumps in the right way,

00:05:39.111 --> 00:05:41.789
you could imagine that one of these pairs

00:05:41.789 --> 00:05:45.632
of this oxygen would then go-

00:05:45.632 --> 00:05:48.772
one of these pairs on
this oxygen would then go

00:05:48.772 --> 00:05:52.727
and essentially form a
bond with this carbon,

00:05:52.727 --> 00:05:58.257
making this carbon
right over here neutral.

00:05:58.257 --> 00:05:59.284
So what is that going to look like?

00:05:59.284 --> 00:06:01.303
And this might happen,
this would happen faster

00:06:01.303 --> 00:06:03.307
so I'm not going to do
this as an equilibrium.

00:06:03.307 --> 00:06:06.489
This could happen like this.

00:06:06.489 --> 00:06:10.308
And let me- let me just
copy and paste the bromine

00:06:10.308 --> 00:06:13.183
so I don't have to redraw the whole thing.

00:06:13.183 --> 00:06:17.313
So, let me copy and let me paste it

00:06:17.313 --> 00:06:19.930
so that's our bromine right over there.

00:06:19.930 --> 00:06:21.580
Draw it right there.

00:06:21.580 --> 00:06:24.606
Actually let me erase that little smudge

00:06:24.606 --> 00:06:27.049
and make sure it still
has a negative charge.

00:06:27.049 --> 00:06:30.093
So, negative charge.

00:06:30.093 --> 00:06:31.376
It's a bromide anion.

00:06:31.376 --> 00:06:34.056
Now let me draw everything else.

00:06:34.056 --> 00:06:36.881
So I have this carbon,

00:06:36.881 --> 00:06:38.547
this carbon, let me
scroll down a little bit

00:06:38.547 --> 00:06:39.722
so I have some space.

00:06:39.722 --> 00:06:41.672
Carbon, I have the carbon in the back.

00:06:41.672 --> 00:06:43.091
CH3.

00:06:43.091 --> 00:06:44.497
I have the carbon on top.

00:06:44.497 --> 00:06:46.316
CH3.

00:06:46.316 --> 00:06:48.266
I have the carbon in front.

00:06:48.266 --> 00:06:51.968
I have the carbon in front like that.

00:06:51.968 --> 00:06:53.775
CH3.

00:06:53.775 --> 00:06:55.339
And now my oxygen,

00:06:55.339 --> 00:06:57.477
or I should say this
molecule right over here,

00:06:57.477 --> 00:07:00.496
the water molecule has
attached to the carbon.

00:07:00.496 --> 00:07:03.644
So these 2 electrons,

00:07:03.644 --> 00:07:05.785
you could say they've attacked the carbon.

00:07:05.785 --> 00:07:08.702
They now form a bond with the carbon.

00:07:08.702 --> 00:07:11.180
So these are those 2 electrons

00:07:11.180 --> 00:07:12.899
in this covalent bond.

00:07:12.899 --> 00:07:14.779
And now let's draw the rest of this.

00:07:14.779 --> 00:07:16.714
So you have the oxygen.

00:07:16.714 --> 00:07:18.532
You have these 2
electrons right over here.

00:07:18.532 --> 00:07:20.153
These 2 valence electrons.

00:07:20.153 --> 00:07:24.948
Then you have 1 hydrogen
and then another hydrogen.

00:07:24.948 --> 00:07:27.961
Now what is going to be the charge,

00:07:27.961 --> 00:07:29.348
what is going to be the charge

00:07:29.348 --> 00:07:31.089
right over here on the oxygen?

00:07:31.089 --> 00:07:33.946
Well it was, it had a
partial negative charge

00:07:33.946 --> 00:07:35.527
because it's more electronegative

00:07:35.527 --> 00:07:39.056
but it just gave, it just gave the

00:07:39.056 --> 00:07:40.841
essentially half of a bond,

00:07:40.841 --> 00:07:41.808
half of a pair.

00:07:41.808 --> 00:07:44.674
It's now sharing a pair with this carbon.

00:07:44.674 --> 00:07:46.985
So it's equivalent to
giving up 1 electron's

00:07:46.985 --> 00:07:48.941
equivalent of charge so you would now say

00:07:48.941 --> 00:07:52.762
that this thing right now has a positive,

00:07:52.762 --> 00:07:54.374
a positive charge.

00:07:54.374 --> 00:07:56.259
So you could imagine,

00:07:56.259 --> 00:07:57.437
you could imagine,

00:07:57.437 --> 00:08:00.084
maybe another water molecule comes along

00:08:00.084 --> 00:08:01.816
maybe another water molecule comes along.

00:08:01.816 --> 00:08:04.480
Let me draw a water
molecule right over here.

00:08:04.480 --> 00:08:05.424
We're sitting in water

00:08:05.424 --> 00:08:07.610
so there's plenty of water molecules.

00:08:07.610 --> 00:08:11.576
So another water molecule might come along

00:08:11.576 --> 00:08:14.646
and say, okay well this
thing right over here

00:08:14.646 --> 00:08:20.123
is positive but the oxygen
is hogging these bonds

00:08:20.123 --> 00:08:21.531
a little bit more than the hydrogen,

00:08:21.531 --> 00:08:24.064
especially now that it's become positive.

00:08:24.064 --> 00:08:28.529
So this might give its
pair to a hydrogen proton

00:08:28.529 --> 00:08:30.169
and then this hydrogen-

00:08:30.169 --> 00:08:31.741
and then this bond with the hydrogen

00:08:31.741 --> 00:08:36.152
will go entirely, entirely to the oxygen.

00:08:36.152 --> 00:08:38.376
Let me draw that in a different color.

00:08:38.376 --> 00:08:41.402
So this bond, this bond right over here,

00:08:41.402 --> 00:08:44.561
goes entirely, goes
entirely to the oxygen.

00:08:44.561 --> 00:08:47.020
Electronegativity means
that if this is more

00:08:47.020 --> 00:08:48.869
electronegative than that
then if a bond breaks

00:08:48.869 --> 00:08:52.447
that pair is more likely to
go to the more electronegative

00:08:52.447 --> 00:08:55.602
the more electronegative molecule.

00:08:55.602 --> 00:08:58.419
Or I should say the more
electronegative atom.

00:08:58.419 --> 00:09:01.391
So what will this look like
when all is said and done?

00:09:01.391 --> 00:09:04.394
So let's draw an arrow like this.

00:09:04.394 --> 00:09:07.598
So let me draw my main molecule.

00:09:07.598 --> 00:09:09.361
So I have the carbon.

00:09:09.361 --> 00:09:12.574
It had bonded to another
carbon right up there,

00:09:12.574 --> 00:09:15.693
which bonded to another
carbon right over there.

00:09:15.693 --> 00:09:18.293
We have our carbon in front.

00:09:18.293 --> 00:09:21.405
We have our carbon in
front just like that.

00:09:21.405 --> 00:09:24.373
We have the bond with our oxygen.

00:09:24.373 --> 00:09:28.894
So we have our bond with
our oxygen right over there.

00:09:28.894 --> 00:09:30.525
So that's our oxygen.

00:09:30.525 --> 00:09:32.878
We have this bond with a hydrogen.

00:09:32.878 --> 00:09:34.410
This bond with a hydrogen.

00:09:34.410 --> 00:09:38.861
We have this pair and now
it has gained this pair.

00:09:38.861 --> 00:09:42.066
It has gained this pair
that was with that hydrogen.

00:09:42.066 --> 00:09:45.108
So just like this, this is now neutral.

00:09:45.108 --> 00:09:46.508
It went from being positive.

00:09:46.508 --> 00:09:49.160
Over here it only had half of this bond

00:09:49.160 --> 00:09:52.076
so it's kind of the equivalent
of 1 electron charge.

00:09:52.076 --> 00:09:53.767
Now it has the whole bond.

00:09:53.767 --> 00:09:55.067
So now it has the equivalent,

00:09:55.067 --> 00:09:56.944
it literally has both electrons.

00:09:56.944 --> 00:09:59.563
Now this thing is neutral

00:09:59.563 --> 00:10:01.579
and now this molecule right over here

00:10:01.579 --> 00:10:04.081
becomes a hydronium cation.

00:10:04.081 --> 00:10:05.634
Let me draw that.

00:10:05.634 --> 00:10:07.535
So this water, let me see.

00:10:07.535 --> 00:10:09.727
That's the 2 hydrogens right over there.

00:10:09.727 --> 00:10:12.512
This is that pair that is on top

00:10:12.512 --> 00:10:18.223
and now it is sharing this pair

00:10:18.223 --> 00:10:20.531
with the hydrogen
essentially with a proton.

00:10:20.531 --> 00:10:24.637
So with the hydrogen, with
this hydrogen right over here.

00:10:24.637 --> 00:10:27.746
With this hydrogen right over here

00:10:27.746 --> 00:10:30.065
and now this will have a positive charge.

00:10:30.065 --> 00:10:33.303
This is a hydronium, this
is a hydronium cation.

00:10:33.303 --> 00:10:35.233
Maybe this bumps into
another water molecule

00:10:35.233 --> 00:10:36.333
and does the same thing with it

00:10:36.333 --> 00:10:38.793
and it just keeps going on and on and on.

00:10:38.793 --> 00:10:41.598
And of course, we can't forget,

00:10:41.598 --> 00:10:45.776
we can't forget our bromide anion friend.

00:10:45.776 --> 00:10:48.946
So there's our bromide anion friend.

00:10:48.946 --> 00:10:50.923
We've got a negative
charge right over there

00:10:50.923 --> 00:10:52.665
and so what are we left with?

00:10:52.665 --> 00:10:54.615
Well we are left with,

00:10:54.615 --> 00:10:55.769
well there's a little bit of,

00:10:55.769 --> 00:10:59.398
there's this hydronium cation
that has a positive charge.

00:10:59.398 --> 00:11:01.841
We have this bromide anion

00:11:01.841 --> 00:11:05.184
and now what is this molecule now called?

00:11:05.184 --> 00:11:06.907
Well we'll go into more
detail in the future

00:11:06.907 --> 00:11:09.340
but when you have a
hydroxyl group attached

00:11:09.340 --> 00:11:11.031
to the carbon backbone,

00:11:11.031 --> 00:11:12.886
it is an alcohol

00:11:12.886 --> 00:11:14.767
and so our main backbone once again

00:11:14.767 --> 00:11:16.992
has 1, 2, 3 carbons.

00:11:16.992 --> 00:11:18.801
So that tells us prop-

00:11:18.801 --> 00:11:20.686
and instead of just saying propane,

00:11:20.686 --> 00:11:22.535
it's propanol.

00:11:22.535 --> 00:11:24.317
So let's write that down.

00:11:24.317 --> 00:11:30.367
This is prop- prop- prop- an

00:11:30.367 --> 00:11:32.259
and some people say
just propanol generally

00:11:32.259 --> 00:11:34.008
but if want to be a little bit particular,

00:11:34.008 --> 00:11:35.887
this is the hydroxyl group

00:11:35.887 --> 00:11:38.223
is attached to the number 2 carbon

00:11:38.223 --> 00:11:43.676
so we would say propan- 2 -ol.

00:11:43.676 --> 00:11:46.591
And of course we still
have this blue methyl group

00:11:46.591 --> 00:11:53.236
so we could say 2 methyl, 2 methyl,

00:11:53.236 --> 00:11:54.463
actually let me make this

00:11:54.463 --> 00:11:59.776
2 methyl propan 2 ol is
what we are left with.

00:11:59.776 --> 00:12:02.406
Now let's think about what we can name

00:12:02.406 --> 00:12:05.148
what we can name this
reaction we just saw.

00:12:05.148 --> 00:12:08.135
Well we've just substituted a bromo group

00:12:08.135 --> 00:12:09.829
with a hydroxyl group

00:12:09.829 --> 00:12:11.409
so I think it's reasonable to say

00:12:11.409 --> 00:12:14.689
that this is going to be
a substitution reaction.

00:12:14.689 --> 00:12:17.212
Substitution.

00:12:17.212 --> 00:12:19.439
And we substituted with a-

00:12:19.439 --> 00:12:20.991
it was a weak nucleophile,

00:12:20.991 --> 00:12:23.197
but it was a neucleophil none-the-less.

00:12:23.197 --> 00:12:25.872
So it involved a neucleophile.

00:12:25.872 --> 00:12:28.253
Nucleophile.

00:12:28.253 --> 00:12:31.496
But this one, unlike the Sn2 reaction,

00:12:31.496 --> 00:12:33.142
in the rate determining step,

00:12:33.142 --> 00:12:34.291
and this is the rate determining step.

00:12:34.291 --> 00:12:36.553
This is the slowest step of the process.

00:12:36.553 --> 00:12:39.022
Everything else will just
kind of start happening

00:12:39.022 --> 00:12:40.248
once this thing happens.

00:12:40.248 --> 00:12:41.807
This thing kind of is an equilibrium.

00:12:41.807 --> 00:12:43.457
This is the rate determining step.

00:12:43.457 --> 00:12:45.514
Only one reactant is involved

00:12:45.514 --> 00:12:47.280
in the rate determining step.

00:12:47.280 --> 00:12:53.065
One reactant in rate determining step.

00:12:53.065 --> 00:12:55.691
Rate determining step.

00:12:55.691 --> 00:12:58.166
In this case, it was the bromo group.

00:12:58.166 --> 00:13:00.625
So you might guess what
we're going to call it.

00:13:00.625 --> 00:13:03.832
It's substitution involving a nucleophile

00:13:03.832 --> 00:13:05.969
so nucleophilic substitution.

00:13:05.969 --> 00:13:08.109
You can imagine this
stands for nucleophilic

00:13:08.109 --> 00:13:11.749
and only one reactant is involved

00:13:11.749 --> 00:13:14.236
in the rate determining step.

00:13:14.236 --> 00:13:16.801
So this right over here,
this whole reaction

00:13:16.801 --> 00:13:20.801
that we've now drawn is an Sn1 reaction.