So our goal here is to figure out how to write orbital filling
diagrams which are really just another representation. Like electron configurations.
We want to see where those electrons are around the nucleus of an atom
To learn and remember this you really need to practice
so I'll do an example of an orbital diagram and then we can work through several together.
Let's do the orbital diagram for Sodium,
Na. So when we look at Sodium on the periodic table its atomic number is 11.
The atomic number that's equal to the number of protons and for neutral elements. That's
the same as the electrons. We know that this is neutral there's no positive or negative sign.
After and all of the elements on the periodic table they're written as neutral.
So we have 11 electrons and we'll spread those out in our orbital diagram here.
You can think of the nucleus as being here and then we have these energy levels around it.
So we have 11 electrons we'll put 2 in the 1s. And note that when we draw this symbol here
we really mean it's an arrow, same for this, this is also an arrow and they're representing
that we have two electrons with opposite spins. So we put 2 and the 1s s orbitals can hold 2.
We'll put 2 here in the 2s so we've used 4 we have 11. We'll spread them out in the 2p.
We've used 10 and then the last one we put in the 3s and this is the orbital filling
diagram for Sodium. If we wanted to write the electron configuration we'd have 1s2
2s with 2 electrons in it 2p with 6 p holds up to 6 and then 3s has 1. So this is the electron
configuration for Sodium. You could also write the orbital diagram like this.
Both the orbital diagram and the electron configuration, they're just telling us the same
information where those electrons are around the nucleus of an element. If you need help writing
electron configurations here there's a link in the description and at the end of this video.
So pause and give this one a try. Chlorine. And remember we have 17 protons since this
is neutral we'll have 17 electrons. s orbitals hold 2 p's can hold up to 6.
So we'll start with our 1s. We have 2. Next energy level 2s. that holds 2 2p we always spread them out
before we pair them up. We've used ten we have seven more. We have our three s so we have five
more, one two three spread them out four five and this is the orbital diagram for chlorine.
If we wanted to write the electron configuration that would look like this.
And for that orbital diagram in this linear fashion we'd
have. But what if we had the chlorine anion? This negative ion. If this was negative
that wouldn't change the number of protons but it would change the electrons. So because this is
negative we'd have one more electron. Electrons are negative we have an extra one here so we could put
that right here and that would fill the third energy level that would make this very stable.
That's why chlorine gains one electron when it forms ionic bonds with other elements.
Then we need to put our other electron here and then we could change this
to a six this would be the electron configuration of the chloride ion Cl-
Pause and give this one a try. Write the orbital filling diagram for fluorine.
So for fluorine the atomic number is nine that means nine protons.
And because it's neutral nine electrons. Let's spread them out one s two two s two
we've used 4 we need 5 more so we spread them out and then double them up pair them up. And this is
the orbital diagram for Fluorine. If we write the electron configuration we have 1 1s2 2s2 2p5 .
Pause and rewrite this for the fluoride ion. The fluorine when it gains an extra electron.
so for the fluoride ion F- gained an extra electron so we'll put that right here.
Now the second energy level that's full. Let's change this to a six and this is our electron
configuration for the Fluoride ion and this is our orbital diagram again we're just trying to show
where the electrons are around the nucleus here. Let's try another one.
So for Calcium. Pause first do the orbital diagram then the electron configuration
and then the orbital diagram in this more linear fashion so we have 20 total electrons for calcium
this is our orbital diagram. And then we can use this to write the electron configuration.
And that's the orbital diagram electron configuration or calcium.
But what if Calcium formed an ion? Would it gain or lose electrons?
it turns out that calcium is going to lose these two electrons here
and since it's lost electrons it'll be Ca 2+ so we'll get rid of this here and because
calcium lost those two electrons this energy level here the third energy level the third
energy level is full it's got eight electrons so that's why calcium forms these 2+ ions.
So pause and give Iron a try. We have 26 protons so 26 electrons spread them out here
and then when we get to our d orbital we're going to spread them out
d can hold up to 10 and then double them up we've used all 26 of our electrons.
This is our orbital diagram. If we wrote the electron configuration it would look like this.
When we talk about charges with metals transition metals they will be positive it's a little bit
more complicated though there's a link in the description to this video that discusses how
to write the orbital diagrams for transition metals. So to recap all we're really trying to
do here with these orbital filling diagrams these electron configurations we're trying to describe
where the electrons are around the nucleus of an atom as well as the energy levels for these
electrons. The key is to look at the atomic number find the number of electrons and then spread them
out in the orbital diagram. You can start with an electron configuration if that's easier for you or
with the orbital diagram and then write electron configuration. This is Dr. B and thanks for watching!