Orbitals and Electrons
Electron configurations Introduction to using the periodic table to determine electron configurations
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- 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.
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