In the last couple of videos
we figured out the electron configurations for atoms
that only had electrons in the S and P subshells.
and so we have this obvious problem
we also have the D subshell
which we'll talk about here with these bizarre shapes
And eventually we even get into the F subshells
which are these really kinda exotic looking shapes
and these shapes
they're interesting to look at and think about.
but they're not as important
for actually figuring out the configuration.
so the question arises
what happens when we start
going to the D and F subshells.
The general way to think about it
is the energy shell you're in
is equivelant to the period,
we are in the periodic table
so if we were to do... so just it all fits on one page...
the periods would appear here on the left
but then I wouldn't be able to finish the whole table
So this is period one
let me write this in a darker color.
Period one, two, three, four, five, six
I think I barely am fitting on the page.
So each row is a period
and then for the porposes of
figuring out the electron configuration
we did this in the last video
we want to put helium
let me just copy and paste exactly helium
we want to put Helium in the S block
so we want to put Helium right there
the reason why, just in case you are curios of
why Helium is put there in the periodic table
is because it has very similar properties
to the other elements in this columns or this group
each column is called a group
and we'll talk about valence electrons
and why that leads to different properties
but for electron configuration purposes
we can put it in the S block
and that's not too hard to remember
beacuse it's just one element
and it kind of makes sense，1s1, 1s2, etc.
All you do is draw blocks around them
so, see, this is - I said multiple times already that
this is - this right here is the S block
this over here on the right is the P block
that's the P block
And then this in the middle right here is the D block.
this is the D block.
and so if you want to figure out
the electron configuration of any atom
you just have to... the way you think about it..
they fill in this order, but when you say..
Let's say this, this,
you know when you go from Calcium:
Clacium would have filled out the 4s2 right?
4s1, 4s2, so if I just do it's 4th energy shell
it looks like this.
Calcium is: 4s2..
and the you start filling the D block, right?
Oh, what did I say? I wanted to do... so that's Calcium
instead I wanted to write
the electron configuration for iron
which is in the D block
so turns out
and this is kind of an artifact
and I'll do a more detailed video on this in the future
that it actually goes and backfills the 3rd energy shell
because all of the sudden
the D orbitals can kind of fit in
the gaps of the 3rd energy shell
so what you do is you go one energy shell above it
So whatever period you are in in the d block
you go one minus that.
Sorry, you go that period minus one
to figure out what energy shell the D block is filling
so iron has 1, 2, 3, 4, 5, 6 elements in the D block.
so it's going to have d6,
but it's not going to do 4d6. It's going to be 3d6
And I figured that out because
it's in the fourth period and I subtracted one from that.
so this is kind of the
highest energy 8 electrons in iron.
4s2, 3d6.
If I said what are the electrons
that are in the outer-most energy shell
I would say that there are two electrons
in the outer-most energy shell for iron.
But if I were to say
which energy shell has the highest energy electrons?
It would be these.
Let me actually do the
whole electron configuration for...
let me pick up another one...
let me take, this is Copper right here.
Let me do Copper.
So the most, the highest, energy electrons
it has are going to be 1, 2, 3, 4, 5, 6, 7, 8, 9.
Actually let me not do copper
because copper does something
very interesting in real life
it's one of the few things
that kind of is a special case,
so let me do a different one, let me do ...
let me do the whole thing for iron.
Sorry to be waffling around so much.
If you want to do the entire
electron configuration for iron
it would be 1s2. That‘s the first energy shell
now the second,
let me do that in magenta, right there.
1s2, and then in orange you have 2s2
and then you have 6 in the P section right there
so 2p6.
Now we are in the third energy shell.
The third energy shell
let me go switch to this bluish color.
So then I fill up 3s2, remember this is the S block,
then I fill out 3p6.
fill out those right there: 1, 2, 3, 4, 5, 6.
now I'm going to add these electrons, then I add...
let me pick a nice green.
Then I go to 4s2.
So it's 4s2.
And now this was the interesting thing,
you know, the D block is interesting
Now I fill out another D block,
or my first D block: 1, 2, 3, 4, 5, 6
but it won't be in the 4th energy shell.
It will be in the 4th minus one energy shell:
it will be in the 3rd energy shell
so this will go to 3d6
just like we did at the beginning of the video
and so the 3rd energy shell.
So I would actually write it here.
I could write it, if I wanted to write.. 3d6.
So if I wanted to write things in order of
which energy shell they are
I could have wirtten it this way
If I wanted to write it in order of
the highest energy electron...
remember the shells are kind of
the best way to visualize
how far away we are from the nucleus,
so, in this case,
these higher energy electorns
are going to be further in the nucleus
even though they take..
it's a higher energy state to be in.
If I did it in terms of energy state
I could rearrange these two
but in most of chemistry
what matters is what's in the outter shell
so it's interesting that
although with filled outer 4s2 here
and then we kept adding more and more electrons,
those electrons where just filling a lower energy shell,
so if we.. in this atom, in case of Iron,
when we talk about the electrons
in this outer energy shell
and thoses are called the Valence Electrons
and these are the ones that react.
These are called Valence...
let me use a better color...
Valence Electrons.
This iron has 2 valence electrons,
because the outer shell is 4s2.
Even though it had these...
even after filling 4s2 it had 6 more electrons.
but those kind of backfilled the third energy shell
so that's one way, and than you might say:
oh well what happens when we go to the F shell?
Or the F block?
So that's these down here..
In a lot of periodic tables
you see these Lanthanoids and Actinoids down here
and they are supposed to fill in the gap right here
and that might be a little hard to visualize
and I'll show you why they do this.
You could just as easily made a periodic table
that looks like this.
where you insert them in,
you push everything to the right
and you insert these in
but obviously this kind of periodic table
is a lot harder to fit in
you could have done the same thing
with the D block actually
This one is the S block, this is the F block
and this is the D block
and then this is the P block right here.
when we are dealing with the F block,
so let's say we wanted to figure out..
I don't even know what element this is...
the electron configuration for this atomic symbol La
So it first it's filling out...
this last incremental electron fills the F block.
So it's F - let me do it in a lower case.
It has one in the F orbital,
and this is the 6th period
but with the F block you subtract two.
You subtract 2 from it so it'll be 4f1, and then 6s2.
The S block you just look at the period, 6s2
And then if you were to keep going back
you would then go to 5p6
so then it would be 5p6
and then it would fill out these 10
in the D block right there that are in the 5th period
but remember you subtract one from the D block
so it'd be 4d10
and then it's 5s2
and you just keep going back that way,
and it seems complicated at first but just remember
when you are in the S or the P block
you just look at the period you are in
but then when you start filling the D block
it fills in a subshell that's one lower
and when you start fillng the F block
which are these really large elements
you start fillng a subshell that is two lower
so maybe in the next video
I'll do a couple of these electron configurations
because I think I'm already out of time
and I'll actually show another way to figure this out
that's often covered in some chemistry classes.