Electronic Configuration of f - Block Elements Video Lecture - JEE

Lecturer: Let's do a warm up where we
figure out the electron configuration
of Xenon right over here
and then we can use that
as the basis for starting to explore the
electron configurations
of F block elements.
And in particular, we'll try to figure out
the electron configuration of Neodymium.
I always have trouble pronouncing these.
Neodymium I believe is
how it's pronounced.
So let's first work on Xenon.
I encourage you to
actually pause the video
and try to come up with the
electron configuration
for Xenon on your own.
So I'm assuming you've had a go at it
so we can just go through it.
So it's going to be one S two then
we go to the second period.
Two S two and then we're
going to the two P subshell.
So one, two, three, four, five, six.
Two P six then three s two then
three p six then we go four s two
and now we are in the D block.
And remember, the D
block, even though we're
in the fourth period, we're going to
actually fill in the three D subshell.
We take the period minus
one, so it's going to be
three D, and to fill it up we have
one, two, three, four, five, six,
seven, eight, nine, 10, three D 10.
Then you're back in the P block
and since you're in the fourth period,
it's gonna be four P, and once again to
fill it up, you have six electrons.
And then we go to the fifth period.
Five S two and then we're going to go...
The period is five but
we're in the D block
so we're going to go back
to the four D subshell.
Four D 10 and then we come back and Xenon
perfectly fills out the five P subshell.
Five P six.
So that's the electron
configuration of Xenon.
So now let's think about what the
electron configuration of Neodymium is.
So one thing that you're saying, "Hey,
"what's going on with this
F block right over here?
"Just kind of this island of elements."
And it's really not an island.
The reason that they put these colors here
is because the F block actually belongs
right here and if people had more width on
pages to display these periodic tables,
they would shove the D and the P blocks
over to the right and
stuff the F blocks right over here.
And we actually did that and I actually
like to look at it that way because
it makes it clear it's
not really an island
and it actually kind of fits
in the pattern of the periodic table.
That is right over here.
This right over here is our F block.
So that is our...
This right over here is our f block.
So given that, lets figure out
the electron configuration for Neodymium.
And I'll give you a hint.
In the D block you go back and back fill
one subshell below the
one shell below the period that you're in.
In the F block you go two,
you go back two shells.
So here, we're not filling
out the six F subshell,
not even the five F subshell,
but the four F subshell.
So given that, figure out
how much more do we have to add.
How much more do we have to go past Xenon
in order to get its
electron configuration.
So I encourage you to pause the video
and figure that out
right now for Neodymium.
So I'm assuming you've had a go at it.
So Neodymium is going to have the
electron configuration of Xenon
so Xenon gets us right over.
It's the highest atomic
number noble gas that
has a smaller atomic
number than Neodymium.
So we can start with that, which we
already saw is fairly involved.
And then to that we just add
the incremental higher energy electrons.
So now we're in the sixth period so
we're gonna go six S two,
that's that right over there.
That's six S two and now we're filling,
we're gonna start going into
the F subshell but it's not
gonna be the sixth
shell, it's gonna go two.
It's gonna be our period minus two
so it's gonna be four.
Let me use a color you can see.
So this gonna be, we are
four electrons into that subshell.
One, two, three, four so
it's gonna be four F four.
So we're in the sixth period but
since we're in the F block, we're gonna
go back, fill it to the fourth shell.
That's the fourth shell right over there.
And we are one, two, three, four,
four electrons into it.
And so this is neat shorthand because
the other way to write
the electron configuration
of Neodymium would have been to do this.
Would have been to write down
all of this, let me do that.
To have all of this, let
me copy and paste it.
Actually I think that's going to take
up too much space, let's see.
So.
To write all of that, copy and paste.
To write all of that and then
to add to that the six S two.
Six S two and the four F four.
Four F four and so hopefully you
appreciate that this is a slightly
more efficient way to write it.