- [Instructor] In many videos
we have already talked
about electron configuration
and now in this video
we're going to extend that understanding
by thinking about the electron
configuration of ions.
These are going to be charged atoms.
Let's just start looking at some examples.
Let's say we are dealing with fluorine.
Now, we know what a
neutral fluorine atom's
electron configuration would be.
In fact, if you want a
little bit of practice,
try to pause this video
and think about what is
the electron configuration
of a neutral fluorine atom?
All right, now let's work
through this together.
A neutral fluorine atom
has nine electrons,
and we could just use our
Periodic Table of Elements.
So first, we're going to
have two electrons in 1s.
So we'll have 1s two.
And then we're going to
go to the second shell.
So then we go to 2s two.
So far we have filled in four electrons.
And next we got to the 2p sub-shell.
And we are going to have,
we're talking about a neutral fluorine,
we are going to have one two
three four five electrons
in that 2p sub-shell.
So it's 2p five.
So if that's the electron
configuration for fluorine,
what do you think the
electron configuration
for fluoride would be?
This is just the anion that
has one extra electron.
It is a negatively charged ion.
Pause this video and try to figure it out.
Well, here you're now going
to have one extra electron.
The fluorine has nabbed
an electron from someplace
and so where will that extra electron go?
Well our 2p sub-shell has
space for one more electron.
So that's where it will go.
So the fluoride anion is going to have
an electron configuration
of 1s two, 2s two, 2p,
now it's going to have an
extra electron here, 2p six.
2p six.
Now let's do another example.
Let's say we wanted to figure
out the electron configuration
of a part positively charged calcium ion.
So calcium, let's make it two plus.
It has a positive charge of two.
You could do this as a neutral calcium
that has lost two electrons.
What would be its electron configuration?
Pause this video and
try to figure that out.
All right, well one way
to figure this out is
first we could figure out
the electron configuration
of a neutral calcium atom
and then from that, we can take two
of the highest energy electrons away.
And so neutral calcium, you could view it,
actually let's do it in
noble gas configuration.
Neutral calcium, the noble gas that comes
right before calcium is argon.
So it's going to have the
electron configuration of argon
and then we are going
to have two electrons
for that fourth shell.
It's going to fill in the 4s sub-shell.
And so we're going to have argon
and then we're going to have,
let me do this in a new color,
let's call this 4s two.
Now what do you think is going to happen
if we were to lose two electrons?
Well those two electrons
in that 4s sub-shell,
in the fourth shell, are gonna go away.
And so the electron configuration here
for calcium with a positive two charge,
this calcium cation, is going to be
the electron configuration
of argon and no 4s two.
So it's actually going to have
the exact same electron
configuration as argon.
So I will leave you there,
just a couple of examples.
And I encourage you,
if you're in the mood,
just pick any of these
atoms, any of these elements,
and think about what would happen
if they gained or lost an electron
and what their electron
configurations might be.
