[Script Info]
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[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.12,0:00:02.97,Default,,0000,0000,0000,,- [Lecturer] As we continue\Ninto our journey of chemistry,
Dialogue: 0,0:00:02.97,0:00:05.43,Default,,0000,0000,0000,,we're gonna gain more\Nand more appreciation
Dialogue: 0,0:00:05.43,0:00:07.17,Default,,0000,0000,0000,,for the periodic table of elements.
Dialogue: 0,0:00:07.17,0:00:09.57,Default,,0000,0000,0000,,We're gonna realize that it\Ngives us all sorts of insights
Dialogue: 0,0:00:09.57,0:00:11.85,Default,,0000,0000,0000,,about how different elements\Nrelate to each other.
Dialogue: 0,0:00:11.85,0:00:14.43,Default,,0000,0000,0000,,And we're gonna talk about\None of those insights,
Dialogue: 0,0:00:14.43,0:00:17.19,Default,,0000,0000,0000,,and that's atomic radii trends.
Dialogue: 0,0:00:17.19,0:00:18.48,Default,,0000,0000,0000,,So we're gonna talk about,
Dialogue: 0,0:00:18.48,0:00:21.15,Default,,0000,0000,0000,,by looking at the act table of elements,
Dialogue: 0,0:00:21.15,0:00:26.15,Default,,0000,0000,0000,,can we deduce how the\Ndifferent sizes of these atoms
Dialogue: 0,0:00:26.37,0:00:28.20,Default,,0000,0000,0000,,might relate to each other?
Dialogue: 0,0:00:28.20,0:00:30.72,Default,,0000,0000,0000,,So let's just start with\Nthe group one elements
Dialogue: 0,0:00:30.72,0:00:31.56,Default,,0000,0000,0000,,right over here.
Dialogue: 0,0:00:31.56,0:00:34.74,Default,,0000,0000,0000,,So we're in this first column.
Dialogue: 0,0:00:34.74,0:00:37.32,Default,,0000,0000,0000,,What do you think is going\Nto happen to the radius
Dialogue: 0,0:00:37.32,0:00:41.19,Default,,0000,0000,0000,,of these atoms as we go\Ndown this first column?
Dialogue: 0,0:00:41.19,0:00:45.06,Default,,0000,0000,0000,,As we go from hydrogen to\Nlithium, sodium, potassium,
Dialogue: 0,0:00:45.06,0:00:46.62,Default,,0000,0000,0000,,so on and so forth?
Dialogue: 0,0:00:47.70,0:00:49.80,Default,,0000,0000,0000,,Well, you might be thinking,\N"Well, as we go down this,
Dialogue: 0,0:00:49.80,0:00:52.02,Default,,0000,0000,0000,,we're adding a lot more electrons."
Dialogue: 0,0:00:52.02,0:00:53.22,Default,,0000,0000,0000,,The outermost electrons,
Dialogue: 0,0:00:53.22,0:00:55.50,Default,,0000,0000,0000,,even though we have the same\Nnumber of valence electrons,
Dialogue: 0,0:00:55.50,0:00:58.86,Default,,0000,0000,0000,,we have one valence electron\Nfor everything in group one,
Dialogue: 0,0:00:58.86,0:01:00.90,Default,,0000,0000,0000,,that one valence electron is at a higher
Dialogue: 0,0:01:00.90,0:01:02.16,Default,,0000,0000,0000,,and higher energy level.
Dialogue: 0,0:01:02.16,0:01:05.64,Default,,0000,0000,0000,,It is at a further and\Nfurther out energy shell.
Dialogue: 0,0:01:05.64,0:01:09.87,Default,,0000,0000,0000,,And so one way to think about\Nit is, if you have the nucleus
Dialogue: 0,0:01:09.87,0:01:11.67,Default,,0000,0000,0000,,of an atom here
Dialogue: 0,0:01:11.67,0:01:15.12,Default,,0000,0000,0000,,and you have that one\Nvalence electron out here,
Dialogue: 0,0:01:15.12,0:01:17.46,Default,,0000,0000,0000,,well, the more that\Nyou go down this group,
Dialogue: 0,0:01:17.46,0:01:20.76,Default,,0000,0000,0000,,you're gonna have more\Nelectrons in between,
Dialogue: 0,0:01:20.76,0:01:21.75,Default,,0000,0000,0000,,in between... (chuckles)
Dialogue: 0,0:01:21.75,0:01:23.25,Default,,0000,0000,0000,,This is a pretty messy drawing.
Dialogue: 0,0:01:23.25,0:01:26.88,Default,,0000,0000,0000,,In between that nucleus\Nand that valence electron.
Dialogue: 0,0:01:26.88,0:01:29.61,Default,,0000,0000,0000,,And that valence electron\Nis going to be further
Dialogue: 0,0:01:29.61,0:01:33.09,Default,,0000,0000,0000,,and further out because it's\Nat a higher energy level.
Dialogue: 0,0:01:33.09,0:01:36.48,Default,,0000,0000,0000,,So because of that,\None, you have shielding
Dialogue: 0,0:01:36.48,0:01:39.63,Default,,0000,0000,0000,,from these inner electrons\Nfrom that positive nucleus,
Dialogue: 0,0:01:39.63,0:01:42.39,Default,,0000,0000,0000,,and this is at a higher\Nand higher energy level.
Dialogue: 0,0:01:42.39,0:01:46.71,Default,,0000,0000,0000,,As you go down this group,\Nthe radius increases.
Dialogue: 0,0:01:46.71,0:01:48.39,Default,,0000,0000,0000,,So let me write that down.
Dialogue: 0,0:01:48.39,0:01:49.71,Default,,0000,0000,0000,,Increases.
Dialogue: 0,0:01:49.71,0:01:50.61,Default,,0000,0000,0000,,What are we talking about?
Dialogue: 0,0:01:50.61,0:01:53.58,Default,,0000,0000,0000,,We're talking about\Natomic radii increases.
Dialogue: 0,0:01:53.58,0:01:56.94,Default,,0000,0000,0000,,So for example, cesium or,\Nwell, let's go with francium.
Dialogue: 0,0:01:56.94,0:02:01.94,Default,,0000,0000,0000,,Francium is a much larger\Natom than hydrogen.
Dialogue: 0,0:02:02.04,0:02:04.86,Default,,0000,0000,0000,,Now what happens if we\Nwere to go horizontally?
Dialogue: 0,0:02:04.86,0:02:09.15,Default,,0000,0000,0000,,What happens if we were to\Ngo across a period here?
Dialogue: 0,0:02:09.15,0:02:11.19,Default,,0000,0000,0000,,So let me do it in different color.
Dialogue: 0,0:02:11.19,0:02:13.14,Default,,0000,0000,0000,,What if we were to go, if\Nwe were to look at, say,
Dialogue: 0,0:02:13.14,0:02:16.80,Default,,0000,0000,0000,,period four, and if we\Nwere to go from potassium
Dialogue: 0,0:02:16.80,0:02:20.16,Default,,0000,0000,0000,,to the right all the way to krypton?
Dialogue: 0,0:02:20.16,0:02:21.45,Default,,0000,0000,0000,,What do you think is going to happen here?
Dialogue: 0,0:02:21.45,0:02:22.62,Default,,0000,0000,0000,,I mean, think about it for a second
Dialogue: 0,0:02:22.62,0:02:24.48,Default,,0000,0000,0000,,before I explain it to you.
Dialogue: 0,0:02:24.48,0:02:26.70,Default,,0000,0000,0000,,All right, so this is the situation
Dialogue: 0,0:02:26.70,0:02:29.82,Default,,0000,0000,0000,,where we're going to keep adding electrons
Dialogue: 0,0:02:29.82,0:02:31.35,Default,,0000,0000,0000,,as we move to the right,
Dialogue: 0,0:02:31.35,0:02:33.45,Default,,0000,0000,0000,,but you're not going\Nto be adding electrons
Dialogue: 0,0:02:33.45,0:02:36.09,Default,,0000,0000,0000,,to higher and higher energy levels.
Dialogue: 0,0:02:36.09,0:02:37.77,Default,,0000,0000,0000,,You're either going to be backfilling
Dialogue: 0,0:02:37.77,0:02:39.51,Default,,0000,0000,0000,,in the transition elements,
Dialogue: 0,0:02:39.51,0:02:41.46,Default,,0000,0000,0000,,or you're going to be adding electrons
Dialogue: 0,0:02:41.46,0:02:44.28,Default,,0000,0000,0000,,to your valence shell.
Dialogue: 0,0:02:44.28,0:02:47.25,Default,,0000,0000,0000,,So you're not having higher\Nand higher energy electrons,
Dialogue: 0,0:02:47.25,0:02:50.31,Default,,0000,0000,0000,,so they're not gonna be any\Nfurther away from that nucleus.
Dialogue: 0,0:02:50.31,0:02:52.50,Default,,0000,0000,0000,,But as you go from left to right
Dialogue: 0,0:02:52.50,0:02:56.25,Default,,0000,0000,0000,,across one of these periods,\Nyou're adding protons.
Dialogue: 0,0:02:56.25,0:02:59.04,Default,,0000,0000,0000,,So you're making the center of that atom
Dialogue: 0,0:02:59.04,0:03:01.74,Default,,0000,0000,0000,,more and more positively charged.
Dialogue: 0,0:03:01.74,0:03:04.59,Default,,0000,0000,0000,,So it's going to pull in\Nthose outer shell electrons
Dialogue: 0,0:03:04.59,0:03:06.57,Default,,0000,0000,0000,,more and more and more.
Dialogue: 0,0:03:06.57,0:03:09.33,Default,,0000,0000,0000,,So based on that, you would expect to see
Dialogue: 0,0:03:09.33,0:03:14.33,Default,,0000,0000,0000,,that the radius decreases\Nas you go from left to right
Dialogue: 0,0:03:14.88,0:03:17.19,Default,,0000,0000,0000,,along the periodic table of elements.
Dialogue: 0,0:03:17.19,0:03:19.38,Default,,0000,0000,0000,,And we can confirm this intuition
Dialogue: 0,0:03:19.38,0:03:20.85,Default,,0000,0000,0000,,by looking at this plot here.
Dialogue: 0,0:03:20.85,0:03:22.83,Default,,0000,0000,0000,,So what this is doing is
Dialogue: 0,0:03:22.83,0:03:25.98,Default,,0000,0000,0000,,it's plotting every element\Nin the periodic table
Dialogue: 0,0:03:25.98,0:03:28.68,Default,,0000,0000,0000,,of elements based on its atomic number
Dialogue: 0,0:03:28.68,0:03:30.21,Default,,0000,0000,0000,,and its atomic radius.
Dialogue: 0,0:03:30.21,0:03:33.21,Default,,0000,0000,0000,,So for example, this right\Nover here is hydrogen,
Dialogue: 0,0:03:33.21,0:03:36.12,Default,,0000,0000,0000,,and then your atomic number\Nincreases, you're at helium,
Dialogue: 0,0:03:36.12,0:03:37.98,Default,,0000,0000,0000,,and our intuition is correct.
Dialogue: 0,0:03:37.98,0:03:41.37,Default,,0000,0000,0000,,It looks like the radius has decreased.
Dialogue: 0,0:03:41.37,0:03:43.56,Default,,0000,0000,0000,,And then we go into the second period.
Dialogue: 0,0:03:43.56,0:03:47.88,Default,,0000,0000,0000,,And actually, let me just\Nshow each period here.
Dialogue: 0,0:03:47.88,0:03:50.79,Default,,0000,0000,0000,,So if we go into period two here,
Dialogue: 0,0:03:50.79,0:03:52.83,Default,,0000,0000,0000,,lithium has the largest radius.
Dialogue: 0,0:03:52.83,0:03:56.67,Default,,0000,0000,0000,,And as we go from left\Nto right in period two,
Dialogue: 0,0:03:56.67,0:03:59.73,Default,,0000,0000,0000,,we get to smaller and smaller radii.
Dialogue: 0,0:03:59.73,0:04:04.73,Default,,0000,0000,0000,,Now if we go to period three,\Nwe see the same trend again.
Dialogue: 0,0:04:05.52,0:04:10.26,Default,,0000,0000,0000,,So we see, confirmed in the\Nactual data, that trend,
Dialogue: 0,0:04:10.26,0:04:13.05,Default,,0000,0000,0000,,that as you go from left\Nto right on a period,
Dialogue: 0,0:04:13.05,0:04:16.56,Default,,0000,0000,0000,,the radii or the radius decreases.
Dialogue: 0,0:04:16.56,0:04:19.98,Default,,0000,0000,0000,,Now let's think about a group,\Nwhich is where we started.
Dialogue: 0,0:04:19.98,0:04:23.25,Default,,0000,0000,0000,,Well, across or up, down, any group,
Dialogue: 0,0:04:23.25,0:04:25.20,Default,,0000,0000,0000,,if we go to group one right over here,
Dialogue: 0,0:04:25.20,0:04:26.79,Default,,0000,0000,0000,,we see that intuition.
Dialogue: 0,0:04:26.79,0:04:29.97,Default,,0000,0000,0000,,You go from hydrogen to\Nlithium to sodium to krypton,
Dialogue: 0,0:04:29.97,0:04:32.10,Default,,0000,0000,0000,,all the way to cesium here,
Dialogue: 0,0:04:32.10,0:04:35.07,Default,,0000,0000,0000,,we have our radius is increasing
Dialogue: 0,0:04:35.07,0:04:38.34,Default,,0000,0000,0000,,as we're adding higher\Nand higher energy shells.
Dialogue: 0,0:04:38.34,0:04:40.89,Default,,0000,0000,0000,,You see the same thing with group two.
Dialogue: 0,0:04:40.89,0:04:44.58,Default,,0000,0000,0000,,This is the second column in\Nthe periodic table of elements.
Dialogue: 0,0:04:44.58,0:04:47.58,Default,,0000,0000,0000,,So the data confirms our intuition.