In the previous video, we looked
at the electron configurations and
orbital block diagrams for elements
number one through 18 and we listed them.
Now, we're go on to do
elements 19 through 30.
One thing you may have noticed
is that each time that we
increase the atomic number and
go from One element to the next.
All we're doing is adding
one extra electron.
So chemist, just like electrons,
are pretty lazy.
And we don't wanna write all
of this out all the time.
So, for different electron configurations
we can come up with some abbreviations or
we can say condensed noble
gas electron configurations.
For example, Argon here,
we've listed in the previous video and
I've written out the electron
configuration here.
This electron configuration can
be condensed and put in brackets.
So, any time we have a nobel gas electron
configuration we can start with that and
when I put brackets around argon,
I know that I'm representing the first
18 electrons in In this fashion
that we have right here.
So, when I write out
the electron configuration for
potassium, I can say argon 4S1.
So, that's going to say to other
chemists, hey,
we have 1S2S2P63S23P6 then 4S1 so
rather than write out Higher
electron configuration, right here.
I can simply represent that in
brackets like this, with argon.
So, the orbital block diagram is
gonna be very, very similar and
we can just say that for
potassium, it's gonna be 4s1.
For calcium we can abbreviate
the noble gas core the same way.
We need to add one more electron and
it's gonna be argon 4s2.
For Scandium,
we have the argon noble gas core and
it's gonna be 4s23d1.
So, we can give our Argon core here.
Show our 2 4s electrons.
And then the next in line is the 3d.
And it's gonna have 1
electron in that 3d orbital.
For titanium we have the argon core,
then 4s2 3d2,
so when we draw our block diagram,
we draw two electrons in the 4s
and two electrons in the 3d.
Vanadium, add one more electron.
It's gonna be 4s2, 3d3.
That's gonna give us a block diagram
with the 2 electrons in the 4s
and 3 in the 3d.
Chromium we would predict
based on all of these rules
to have an electron configuration
of argon 4s2 To 3d4.
And just when you think you have
everything figured out, and
you're starting to do well in chemistry,
we throw an exception at you.
Because this is not correct, and
chromium is going to have an exception
to the normal counting rules, or
an anomalous electron configuration,
of 4s1, 3d5.
And we can kinda look at this based on
the electron electron repulsions and
the block diagram will give us a little
more insight as to why this might be.
Okay.
When we put in four
electrons in the d orbital
often times a half filled orbital can
give us a little bit of stability and
it's all about how these electrons
are gonna interact with each other.
So, if I have four electrons
written here in this d orbital,
and I list one electron
here in the s orbital and
we put the other electrons here,
we now have all of our electrons.
Electrons spin up and
there's none that are spin paired.
So, there's no spin pairing energy
cost in any of these orbitals.
And we find by representing it this way,
with five unpaired electrons in the 3d,
and one in the 4s that it's actually
lowering energy than if we paired
the 4s,
two electrons paired in the 4s orbital.
And leaving them three d four, so
this is an electron configuration
that is an exception to the rule.
Malibnidum which is right below
chromium in the periodic table is also
gonna see the same exception.
Okay, for
manganese then we now need 25 electrons,
argon is gonna give us 18.
Then we need to go 4s2 3d5.
So, we're right back on
track with what we would normally
expect from our counting rules.
So, we need to completely
fill up the 4s orbital,
and put 1 electron spin up in
In each of the three d orbitals.
For iron, we have the argon configuration.
it's gonna be four s two, three d six.
So, we put both electrons
in the 4s orbital.
And then one, two, three, four,
five 6 in the 3d orbital.
For cobalt,
we have our argon noble gas core,
then 4s2 3d7.
That's gonna give a block diagram
with both electrons in the 4s,
and then we need to put
7 electrons In the 3d.
So, two of those electrons will be spin
paired and three of them will be unpaired.
For nickel, we have our argon
configuration, it's gonna be 4s2 3d8.
So, we have our argon nobel gas chore.
The 4s electron Or the 4s orbital
is filled with two electrons and
we need to put eight
electrons in the d orbitals.
So, this is gonna have two unpaired
electrons in a nickel atom.
Copper is another one of our exceptions.
Copper Upper is not going to be 4s23d9
instead it's gonna be 4s13d10.
So when we draw this electron
block diagram we do not
fill in the s orbital with that second.
Electron.
Instead, we put all ten
electrons in the D orbitals.
So, our 3D shell is completely filled.
For zinc,
we have the argon electron configuration,
and we have 4S2 3D10.
So, for the 4S orbital
block is completely filled with
spin up and spin down electrons.
And then the 3D block is also completely
filled with electrons.
And when we draw these block diagrams.
Diagrams we can see that
the number of unpaired electrons
is gonna vary as we go across
the periodic table, and
magnetic measurements were some
of the reason why we could prove
how the electrons filled in for
chromium copper and how they were
anomalous or they don't abide
by the normal counting rules.
So, by putting electrons around an atom,
we can see over here in these
block diagrams on the right,
how the magnetic properties are gonna
change from one atom to another.
And the transition metals are definitely
gonna exhibit different properties and
different magnetisms as we
go across the series here.
So, this is how we would fill in
all the electron configurations for
elements 1 to 30.
We're gonna see the same trends for
all of the other atoms
in the periodic table.
And in the next video,
we'll discuss how we would write electron
configurations for cations and anions.
