0:00:00.350,0:00:02.930
- [Instructor] So let's talk[br]a little bit about groups

0:00:02.930,0:00:05.890
of the periodic table.

0:00:05.890,0:00:08.550
Now, a very simple way[br]to think about groups

0:00:08.550,0:00:12.210
is that they just are the[br]columns of the periodic table,

0:00:12.210,0:00:14.670
and standard convention is to number them.

0:00:14.670,0:00:16.940
This is the first column,[br]so that's group one,

0:00:16.940,0:00:20.720
second column, third group,[br]fourth, fifth, sixth,

0:00:20.720,0:00:25.720
seventh, eighth, group[br]nine, group 10, 11, 12,

0:00:27.860,0:00:32.860
13, 14, 15, 16, 17, and 18.

0:00:33.870,0:00:35.400
And I know some of[br]y'all might be thinking,

0:00:35.400,0:00:37.460
what about these f-block[br]elements over here?

0:00:37.460,0:00:39.400
If we were to properly[br]do the periodic table,

0:00:39.400,0:00:41.000
we would shift all of these,

0:00:41.000,0:00:44.350
everything from the d-block[br]and p-block rightwards,

0:00:44.350,0:00:48.330
and make room for these f-block elements,

0:00:48.330,0:00:50.950
but the convention is is[br]that we don't number them.

0:00:50.950,0:00:53.030
But what's interesting, why[br]do we go through the trouble

0:00:53.030,0:00:55.040
about calling one of these columns,

0:00:55.040,0:00:57.960
of calling these columns a group?

0:00:57.960,0:01:00.920
Well, this is what's interesting[br]about the periodic table,

0:01:00.920,0:01:03.070
is that all of the elements in a column,

0:01:03.070,0:01:05.690
for the most part, and[br]there's tons of exceptions,

0:01:05.690,0:01:08.370
but for the most part,[br]the elements in the column

0:01:08.370,0:01:11.070
have very very very similar properties,

0:01:11.070,0:01:13.920
and that's because the[br]elements in a column,

0:01:13.920,0:01:15.510
or the elements in a group,

0:01:15.510,0:01:18.490
tend to have the same number of electrons

0:01:18.490,0:01:19.870
in their outermost shell.

0:01:19.870,0:01:22.530
They tend to have the same[br]number of valence electrons,

0:01:22.530,0:01:25.140
and valence electrons and[br]electrons in the outermost shell,

0:01:25.140,0:01:26.720
they tend to coincide, although,

0:01:26.720,0:01:28.210
there's a slightly different variation.

0:01:28.210,0:01:30.940
The valence electrons,[br]these are the electrons

0:01:30.940,0:01:32.800
that are going to react,

0:01:32.800,0:01:35.690
which tend to be the[br]outermost shell electrons,

0:01:35.690,0:01:38.330
but there are exceptions to that,

0:01:38.330,0:01:40.930
and there's actually a lot[br]of interesting exceptions

0:01:40.930,0:01:43.710
that happen in the transition[br]metals, in the D block,

0:01:43.710,0:01:45.310
but we're not gonna go into those details.

0:01:45.310,0:01:46.530
Let's just think a little bit about

0:01:46.530,0:01:49.040
some of the groups that[br]you will hear about,

0:01:49.040,0:01:51.860
and why they react in very similar ways.

0:01:51.860,0:01:53.840
So if we go with group one,

0:01:53.840,0:01:55.360
group one, and hydrogen is a little bit

0:01:55.360,0:01:57.260
of a strange character,

0:01:57.260,0:01:58.560
because hydrogen isn't trying to get

0:01:58.560,0:02:00.110
to eight valence electrons,

0:02:00.110,0:02:01.400
hydrogen in that first shell

0:02:01.400,0:02:05.230
just wants to get to two valence[br]electrons, like helium has,

0:02:05.230,0:02:06.930
and so hydrogen is kind of,

0:02:06.930,0:02:10.350
it's not, it doesn't[br]share as much in common

0:02:10.350,0:02:11.670
with everything else in group one

0:02:11.670,0:02:12.910
as you might expect for, say,

0:02:12.910,0:02:15.100
all of the things in group two.

0:02:15.100,0:02:17.430
Group one, if you put hydrogen aside,

0:02:17.430,0:02:21.940
these are referred to[br]as the alkali metals,

0:02:21.940,0:02:24.800
and hydrogen is not[br]considered an alkali metal,

0:02:24.800,0:02:27.423
so these right over here are the alkali,

0:02:28.500,0:02:30.103
alkali metals.

0:02:31.320,0:02:34.560
Now why do all of these[br]have very similar reactions?

0:02:34.560,0:02:36.750
Why do they have very similar properties?

0:02:36.750,0:02:37.720
Well, to think about that,

0:02:37.720,0:02:40.500
you just have to think about[br]their electron configurations.

0:02:40.500,0:02:44.710
So, for example, the electron[br]configuration for lithium

0:02:44.710,0:02:46.630
is going to be the same

0:02:46.630,0:02:51.170
as the electron configuration of helium,

0:02:51.170,0:02:53.470
of helium, and then,

0:02:53.470,0:02:58.030
you're going to go to[br]your second shell, 2s1.

0:02:58.030,0:02:59.820
It has one valence electron.

0:02:59.820,0:03:03.650
It has one electron in[br]its outermost shell.

0:03:03.650,0:03:04.993
What about sodium?

0:03:06.210,0:03:09.210
Well, sodium is going to have the same

0:03:09.210,0:03:12.003
electron configuration as neon,

0:03:13.260,0:03:16.200
and then it's going to go 3s1,

0:03:16.200,0:03:18.950
so once again, it has[br]one valence electron,

0:03:18.950,0:03:21.240
one electron in its outermost shell.

0:03:21.240,0:03:23.780
So all of these elements[br]in orange right over here,

0:03:23.780,0:03:25.350
they have one valence electron,

0:03:25.350,0:03:27.860
and they're trying to[br]get to the octet rule,

0:03:27.860,0:03:30.880
this kind of stable nirvana for atoms,

0:03:30.880,0:03:33.220
and so you can imagine is[br]that they're very reactive,

0:03:33.220,0:03:35.190
and when they react, they tend to lose

0:03:35.190,0:03:38.450
this electron in the outermost[br]shell, and that is the case.

0:03:38.450,0:03:41.860
These alkali metals[br]are very very reactive,

0:03:41.860,0:03:43.310
and actually, they have[br]very similar properties.

0:03:43.310,0:03:46.790
They're shiny and soft, and actually,

0:03:46.790,0:03:47.960
because they're so reactive,

0:03:47.960,0:03:49.600
it's hard to find them where they haven't

0:03:49.600,0:03:51.530
reacted with other things.

0:03:51.530,0:03:53.960
Well, let's keep looking[br]at the other groups.

0:03:53.960,0:03:57.410
Well, if we move one over to the right,

0:03:57.410,0:04:00.410
this group two right over here,

0:04:00.410,0:04:03.353
these are called the[br]alkaline earth metals.

0:04:04.266,0:04:09.266
Alkaline, alkaline earth metals.

0:04:09.340,0:04:13.880
And once again, they have[br]very similar properties,

0:04:13.880,0:04:16.380
and that's because they[br]have two valence electrons,

0:04:16.380,0:04:19.350
two electrons in their outermost shell,

0:04:19.350,0:04:21.960
and also for them, not quite as reactive

0:04:21.960,0:04:23.570
as the alkali metals,

0:04:23.570,0:04:27.420
but let me write this,[br]alkaline earth metals,

0:04:27.420,0:04:29.640
but for them it's easier[br]to lose two electrons

0:04:29.640,0:04:31.860
than to try to gain six to get to eight,

0:04:31.860,0:04:34.470
and so these tend to also[br]be reasonably reactive,

0:04:34.470,0:04:38.920
and they react by losing[br]those two outer electrons.

0:04:38.920,0:04:42.710
Now something interesting[br]happens as you go to the D-block,

0:04:42.710,0:04:44.510
and we studied this when we looked

0:04:44.510,0:04:46.270
at electron configurations,

0:04:46.270,0:04:48.430
but if you look at the[br]electron configuration

0:04:48.430,0:04:51.250
for say, scandium right over here,

0:04:51.250,0:04:54.350
the electron, let me do it in magenta,

0:04:54.350,0:04:57.420
the electron configuration for scandium,

0:04:57.420,0:04:58.823
so scandium,

0:05:01.070,0:05:02.430
scandium's electron configuration

0:05:02.430,0:05:06.080
is going to be the same as argon,

0:05:06.080,0:05:08.170
it's going to be argon.

0:05:08.170,0:05:10.300
The aufbau principle would tell us

0:05:10.300,0:05:12.150
that the electron configuration,

0:05:12.150,0:05:15.860
we would have the 4s2 just like calcium,

0:05:15.860,0:05:17.520
but by the aufbau principle,

0:05:17.520,0:05:21.400
we would also have one electron in 3d.

0:05:21.400,0:05:24.843
So it would be argon, then 3d1 4s2.

0:05:27.280,0:05:30.670
And to get things in the[br]right order for our shells,

0:05:30.670,0:05:34.510
let me put the 3d1 before the 4s2.

0:05:34.510,0:05:37.320
And so when people think[br]about the aufbau principle,

0:05:37.320,0:05:40.300
they imagine all of these d-block elements

0:05:40.300,0:05:43.000
as somehow filling the d-block.

0:05:43.000,0:05:45.980
Now as we know in other videos,[br]that's not exactly true,

0:05:45.980,0:05:49.340
but when you're conceptualizing[br]the electron configuration

0:05:49.340,0:05:51.270
it might be useful.

0:05:51.270,0:05:54.600
Then you come over here and[br]you start filling the p-block.

0:05:54.600,0:05:59.240
So for example, if you look[br]at the electron configuration

0:05:59.240,0:06:01.810
for, let's say carbon,

0:06:01.810,0:06:05.930
carbon is going to have the[br]same electron configuration

0:06:05.930,0:06:09.410
as helium, as helium,

0:06:09.410,0:06:12.450
and then you're going to[br]fill your s-block 2s2,

0:06:12.450,0:06:13.503
and then 2p one 2.

0:06:15.695,0:06:17.590
So 2p2.

0:06:17.590,0:06:19.600
So how many valence[br]electrons does it have?

0:06:19.600,0:06:21.700
Well, in its second shell,[br]its outermost shell,

0:06:21.700,0:06:24.890
it has two plus two, it[br]has four valence electrons,

0:06:24.890,0:06:28.180
and that's going to be true[br]for the things in this group,

0:06:28.180,0:06:29.340
and because of that,

0:06:29.340,0:06:34.120
carbon has similar bonding[br]behavior to silicon,

0:06:34.120,0:06:36.120
to the other things in its group.

0:06:36.120,0:06:38.630
And we can keep going on, you know,

0:06:38.630,0:06:42.730
for example, oxygen, oxygen and sulfur,

0:06:42.730,0:06:45.840
these would both want[br]to take two electrons

0:06:45.840,0:06:48.620
from someone else because they[br]have six valence electrons,

0:06:48.620,0:06:49.550
they want to get to eight,

0:06:49.550,0:06:51.580
so they have similar bonding behavior.

0:06:51.580,0:06:53.440
You go to this yellow[br]group right over here,

0:06:53.440,0:06:55.490
these are the halogens.

0:06:55.490,0:06:57.100
So there's a special name for them.

0:06:57.100,0:06:59.650
These are the halogens.

0:06:59.650,0:07:01.250
And these are highly reactive,

0:07:01.250,0:07:03.030
because they have seven valence electrons.

0:07:03.030,0:07:03.960
They would love nothing more

0:07:03.960,0:07:06.250
than to get one more valence electron,

0:07:06.250,0:07:07.610
so they love to react, in fact,

0:07:07.610,0:07:09.080
they especially love to react

0:07:09.080,0:07:11.850
with the alkali metals over here.

0:07:11.850,0:07:16.150
And then finally, you get to[br]kind of your atomic nirvana

0:07:16.150,0:07:18.520
in the noble gases here.

0:07:18.520,0:07:20.900
And so the noble gases,[br]that's the other name

0:07:20.900,0:07:25.900
for the group 18 elements, noble gases.

0:07:26.030,0:07:28.560
And they all have the[br]very similar property

0:07:28.560,0:07:29.710
of not being reactive.

0:07:29.710,0:07:30.740
Why don't they react?

0:07:30.740,0:07:32.600
They have filled their outermost shell.

0:07:32.600,0:07:34.220
They don't find the need, they're noble,

0:07:34.220,0:07:35.560
they're kind of above the fray,

0:07:35.560,0:07:40.513
they don't find the need to[br]have to react with anyone else.