to explain color and magnetism in our complex ion exploration challenge the transition models apply crystal field theory okay so the crystal part in the names comes from the fact that the central metal ion is surrounded by a specific arrangement or pattern of ligands in a 3d structure so here you can see we have our central metal ion here and then we have the ligands surrounding it and it can form those different 3d structures okay so a lot of times that 3d portion is thought of as a crystal lattice because of its structure arrangements and that's how you kind of get that crystal portion now the field part of the name comes from the fact that when the ligands are actually approaching this metal ion okay they actually come with their own electric and magnetic fields that of course increase the energy around those orbitals of the metal ion as well so when these ligands approach the metal ion the central metal ion and of course we're talking about the d orbitals of that central metal ion here they are going to have an electric field in their immediate vicinity due to their charge so we know the ligands can come with a negative charge okay so it's going to have its own kind of electrostatic field coming this way towards the central metal ion this one's also going to have its own this one each ligand is going to have its own electric and magnetic field but also they can have like neutral charges but create polar covalent bonds so we know if they do have polar covalent bonds then they have the the ability to have partial positive or partial negative charges so no matter what when it comes to an electrical field you are going to have like a negative field coming from that ligand kind of giving all of that negative charge okay we also have the d orbitals of the cation portion so you really are going to have electrostatic attractions between the metal cation here which is in the center and then the negative charge on the ligands and then we cannot forget that each ligand is going to be acting as a Louis base and donating electrons and so those electrons that they're donating are going to have a certain motion they're going to move in different orbitals and they can spin they can actually be pointed up or down and have different spins as well so those interactions of those electrons donated in the coordinate covalent bond here also can contribute to a magnetic field as well so we're looking at electrostatic attractions that influence the metal basically central ion when these ligands start approaching. and so really since we're talking about the metal central ions what orbitals are we talking about we're talking about d orbital and so essentially we are saying that when these ligands approach with their electrostatic and of course metal magnetic fields towards that metal ion in the center here they're going to influence the d orbitals of that central metal ion causing them to split into different energy okay and that split is going to influence um the shape be influenced by the shape of the complex ion that's formed. So let's get into that a little bit. So of course our focus is going to be the octahedral shape, okay? So we're going to have our metal here.
It can form a bond with, of course, the different ligands, and it's going to be six ligands that can form a bond with. Now when it comes to crystal field theory and the octahedral shape, and crystal field theory in general, but we're going to focus on the octahedral portion, we are thinking about two things. One, we are thinking about orientation.
And then two, we are thinking about the effects of that orientation on the d-orbitals. D-orbitals of what? The central metal ion.
So what about orientation? Well, we know that when the ligands approach, they're going to have their own electric and magnetic fields. That's going to influence the d-orbitals of the metal ions. So when they first approach, when you're talking about... any kind of orientation here you kind of first want to basically orient ourselves okay so we'll to get to this one next let's focus on orientation so first we're going to have our metal ion in the center and we know this metal ion is going to have 5d or okay so there's our 5d orbital now we also know that we're going to have different ligands that are approaching of course your six of them I'm just showing here and these ligands are approaching and they're going to have their own electrical fields.
electrostatic charges and they're also going to have their own magnetic field okay so that's what we're knowing there and these magnetic and electrical fields are going to influence these five D orbital the question becomes how well guess what it depends on the shape of these five D orbitals so we know they all have the same energy which we see here but they also have all different shapes so this represents one shape this also represents one shape and all these three also represents other shapes of the D orbital we know they're made of different lobes and kind of this flow relief shape as well on the x y and z axis so we're thinking about ligands approaching we're thinking about ligands approaching from the x y or z axis Okay, and of course when they do approach it depends on how so if they approach Directly towards the lobes of the d orbitals then they're going to have a specific You know thing that they do if they approach at Between the lobes of the different d orbitals then they're going to do something else So we're going to talk about two approaches the first is going to be Directly towards the lobes and then the other orbitals of the five are going to be um basically how the ligands approach between the loads now why would this happen well it's all about repulsion folks so we have our ligands they have their own electric field of course they also have the electrons that they're donating for the lewis base so they're coming with a lot of negative energy here we also have the metal cations that have their own um electrons within these different orbitals as well and so what we have is a lot of repulsion so these things are going to repel okay so let's think about it if we have the ligands directly going to be creating direct bonds here with the loads of the d orbitals just like we see with this one as well then the repulsion there is going to be way higher versus if we have the ligands making um their bonds these coordinate covalent bonds between the lobes of the d orbitals then the repulsion is much less so we actually have a split we have the ligands can approach directly to the lobes and then the ligands can approach between the lobes and so orientation is going to matter now let's go ahead and get into how that orientation is going to affect these d orbitals a little bit okay all we've known so far is that we are going to have ligands that are going to orient and approach the d orbitals of the central metal ion a specific way so we start off with the 5d orbitals that we see here of the metal ion that have all their different shapes when the ligand approaches energy is going to increase in those five d orbitals so this is going to be our energy diagram as course is going to increase as you see here now again because we have those ligands approaching with their own electrostatic attractions meaning negative charges and their own magnetic fields they're going to approach the d orbitals in a specific way so there's going to be certain d orbitals like this one here and this one here that the ligands are going to approach directly towards the lobes of the orbitals And when that happens, it's going to cause a split in the d-orbitals. So these five d-orbitals are now going to split into two for octahedral. They're going to have two orbitals here, and they're going to be three orbitals here. These two orbitals here are going to be higher in energy. Why are they higher in energy?
It's because the ligands are directly basically going towards the lobes of those d-orbitals here. So they're going to be higher in energy because there's going to be more repulsion. Now, let's also focus on what happens when they're going to be making these metal ligand bonds between the loads. When they're making bonds between the loads, those three orbitals, this one here, this one here, and this one here, are going to be lowering energy. So, yes, because they split into two different types of energies, we do have different names.
So now these two orbitals are going to be called the EG orbitals, and these three orbitals are going to be called the T2G orbitals. and of course this is all for octahedral shape which is what we focus on so again we had our orbitals we had the ligands approach our d orbitals on the metal ion causing them to split if the ligand approached directly on the lobes they split into higher energy orbitals called eg and if the ligand it was to make the metal ligand bond between the lobes they split into lower energy orbitals called t2g so kind of how i remember this for myself if i just say eg orbitals are called elevated, just think E for elevated because they're higher energy, and then T2G, I just think T for three. That means three out of the five orbitals are lower energy, and the other two have to be the higher energy.
So as you can see, we do see a splitting, right? Now we have to kind of add more layers onto that. So before we just said, oh, we have a splitting, now let's kind of add more layers.
We have this splitting, and we see this little delta here. So when we have our d orbitals, one two three four five and they go ahead and split you have the higher two here are eg orbitals and then we have our lower energy orbitals which are three of them t2g they actually create an energy difference so this energy difference is caused by the split okay that split can be called the crystal field effect and when you have high dinner high energy D orbital the low energy do overalls there's going to be that energy difference like we're saying between these two types of orbitals that is called the crystal with that here crystal field splitting energy very splitting energy now a lot of times you will see the Delta sometimes you'll see the Delta over a cathedral sometimes you'll see the Delta CT all because we're focused on how the d-orbitals are split for the octahedral shape if you had other shapes tetrahedral square planar for example then the d-orbitals will split differently but this is for octahedral which is going to be our six ligands that we focus on for this course okay folks so the difference in energy between the two sets of d-orbitals result from electrostatic interactions with the surrounding ligands and this basically makes up our understanding of crystal field theory and so now instead of just saying oh we have um a different d orbitals that are used in bonding now we're saying no we have specific orbitals that are split in energy based on the ligands that are attached to them and because of this and because of this overall theory we're able to see different properties like color and magnetism all based on whatever complex ions we see so now we have to continue to add more layers on what we have here let's get to it folks