9.3 Hybridization

Question 1

Valence bond theory:
* atoms use their unpaired electrons to form bonds (each of 2 atoms is going to chip in an unpaired electron, and that pair of electrons is going to be shared to create a bond)
* The atomic orbitals from both of those atoms over lapping in the process of bond creation

Hydrogens just have 1 electron in the 1s^1 orbital, so those must be the electrons its using for bond creation
* The s orbital is sphyrical in shape.
* So between the two hydrogens their s orbitals over lap and the 2 electrons (from each hydrogen) are going to be in these overlapping orbitals.
* This is what valence bond theory looks at as the creation of a bond

Question 2

Lets look at the H-F bonding

We can see that F doesnt have a full P orbital (1 theres 5 in there, so one is unpaired)
* so the p orbital is what overalps w/ hydrogens S orbital to form the bond

Remember, according to valence bond theory, the overlapping of orbitals is what leads to the creation of a bond

So the 1s orbital from hydrogen is overlapping w/ the 2p orbital on florine

Question 3

Lets look at F-F bonding

So again both the F are missing 1 electron in the p orbital, so their P orbitals overlap to form that molecular bond.

Question 4

So carbon has 4 valence electrons, but below we can see that only 2 of them are unpaired (the 2 in the p orbital are unpaired)

valence bond theory says that an atom is going to use its unpaired electrons to make bonds.
* that would seem to imply carbon would only make 2 bonds, however, we know carbon makes 4 (it has 4 valence electrons, meaning its 4 short of an octet, which is why it tries to make 4 bonds)

It undergoes a “promotion”
* Which means 1 of the 2s electrons is promoted up into a higher energy orbital (moved into 1 of the 2p orbitals which are higher energy than the 2s orbitals)
* Just like when you get a promotion in a company you end up in a higher position, this electron ends up in a higher E position
* NOTE: the reason 2s is lower E than 2p is because it would take more energy to detach an electron in the 2s orbital than 2p because its more attracted to the nucleus (aka it as more negative energy, so its considered lower energy - it would take more enery to remove it).

Great so following the promotion we now have 4 unpaired electrons and carbon is ready to make 4 bonds.

So the p orbitals are like dumbells with one being on the x,y,z axis (theres 3 of them)

So below I only drew 2/3 of the p orbitals, the third isnt needed. This is showing a problem in this
* notice the P orbitals are spaced 90 degrees apart, however in the real methane molecule it would be 109.5 degrees apart, not 90
* So the conclusion that we come to is these p orbitals, cant be the ones involved in overlapping to create these bonds.

What carbon is actually doing here is its taking all its orbitals, and its going to mix and combine them.
* This process is called hybridization

So the 3D dumbell shape that P orbitals are is derieved from equations, making their design.
* If you take these equations, you can combine them, in a process called linear combination. –> its essentially like adding these math functions in different ways.
* It turns out if you mix and match and combine the 4 orbitals we are working with (2s orbital (a circles) and the 3 different versions of the p orbitals [dumbells oriented on the x,y,z axis]) you can combine them 4 different ways –> that leads to the creation of 4 different orbitals
* It turns out these these new orbitals have a little more energy than the 2s orbital and a little less energy than the 2p orbital (this makes sense because its somewhere inebtween these because they were combined)
* These are called SP^3 hydrbids (because they’re made of 1s and 3p orbitals)
* and the number of orbitals you mix together to make the hybrids, thats how many orbitals you’re going to create.
* So we mixed together 4 of them so we must have 4 of them.

The angle of the sp^3 orbitals = 109.5
* and we have 4 of them from carbon, and these are what overlap w/ hydrogen
* I only drew 2 of them below because it would be really hard to draw in a tetrahedral shape with 2 going into the board and one coming out of the board, but you get it.

Question 5

You can look at the # of electron domains and know exactly what the hybridization is.

If you have 4 electron domains, that means you’re going to need 4 hybrid orbitals. 1 for every single electron domain

If you need 4 hybrid orbitals, you’re going to need to mix 4 of your original atomic orbitals.
* if you have 4 electron domains your sp^3 hybridized

Question 6

So again you can look at the # of electron domains and know how many hybrid orbitals you’re going to need to use (shown on next slide)
* this makes since because for something like a tetrahedral it would need 4 places to bond, meaning we’d need 4 hyrbid orbitals where it can bond (all 109.5 degrees apart)

With 3 electron domains you’d still use the lowest energy s orbital, then you’d use 2/3 of the p orbitals, but you’d leave the last one alone
* these 3 sp^2 orbitals would be exactly 120 degrees apart, part of a triginal planar electron domain geometry
* so if you have 3 electron domains, you’re going to be sp^2 hybridized and they will point 120 degrees apart
* **again were talking about carbon with its 4 valence electrons here - its got 3 of them in the hybrid orbitals because it only has 3 electron domains, meaning its only going to be bonding 3 times, that 4th electron is still in the normal p orbital because its not going to be bonding so it doesnt need a hybrid orbital to match a speicifc bond angle. **

If carbon only has 2 electron domains, then it will only need 2 hybrid orbitals.
* so in this case we only need 2 hybrid orbitals because it only has 2 bond twice. It doesnt need to worry about the other 2 electron domains, so we leave them where they are
* So it starts by moving one of the s electrons up into the p orbital.

Below I drew a picture of a Carbon w/ 3 electron domains. It would like like the 2sp^2 orbital w/ the single 2p electron. We will find out later that that 2p electron actually serves a purpose in making the double bond (even though it doesnt speciically have a hybridized orbtial itself)

at the very bottom we have an example of a carbon w/ 2 electron domains
* one is for the lone pairs and the other is for the tripple bond (so both of those take up a sp orbital meaning they use 2 of those hybridized sp orbital)
* So the lone pair gets a hybrid orbital, even though its not actually bonding to anything <– I think this is because of its specific geometry.
* The other 2 bonds in the tripple bond utilize those other 2 electrons in the 2p unhybridized orbitals (so those unhybridized seem to always support the multiple bonds)

Answer 6