Covalent Bonding

chemistry lecture number 37

covalent

bond this lecture has a lot of information so I recommend that you go to this website here and print chemistry lecture number 37 and read it as you see it on the screen well here we go ionic bonds occur between atoms metallic and non-metallic in an ionic bond electrons are transferred from a metallic atom to another non-metallic atom atoms join because they have opposite charges

covalent

bond occurs between two non-metallic atoms in a covalent bond electrons are shared between two atoms Electrons stay together because the electrons that are between the atoms act as glue that holds the positive nuclei together, for example, suppose two hydrogen atoms come close to each other, the electron attached to a hydrogen atom will be attacked by being attracted to the nucleus. of the other hydrogen atom and therefore each electron will be attracted to the nuclei of both atoms so here are two hydrogen atoms a proton with an electron orbiting around it the electron is attracted to the nucleus but what is going to happen is that this electron is also going to be attracted to the nucleus of this other hydrogen atom and it will be attracted in this way right here, in the same way, the electron in this hydrogen atom, while it is attracted to its nucleus, will also be attracted to the nucleus of the other hydrogen atom and there will be a force of attraction right here, so the electrons are like peanut butter and the nuclei are like two slices of bread and the peanut butter holds the bread together and the electrons hold united the nuclei, so the electrons in the middle keep these two nuclei together.

Atoms will overlap orbitals to achieve a covalent bond, for example when hydrogen atoms bond, they overlap with their S orbitals when two s orbitals overlap, it is as if there are two electrons in both s orbitals and this stabilizes the atoms. hydrogen. Remember that a full s orbital makes an atom more stable, so here is a hydrogen atom, here is its electron that is in the s orbital here is another hydrogen atom here is the electron in that missing orbital this sphere that surrounds it is the region of space where the electron moves that is the S orbital so their S orbitals will overlap and after the S orbitals overlap in a certain sense both electrons are now occupying the s orbitals of both hydrogens and when you have two electrons in an S orbital, that is a state of happiness, so the hydrogens are happy because now they each have two electrons in their S orbital, also orbitals are capable of holding two electrons when an orbital with one electron overlaps with another orbital which also has a single electron, both orbitals will now have two electrons and this makes both atoms more stable and therefore when a covalent bond occurs, the single electrons of one atom will pair with single electrons of others atoms too. and the P orbitals in an atom will combine to form a hybrid orbital an S orbital can combine with one, two or three P orbitals, so orbitals can mix when one S orbital combines with three P orbitals it looks like this , so here is our orbital answer here there are three P Orbitals, you combine these orbitals and you get an sp3 hybrid, so P 3 indicates that there are three P orbitals that combine with a single S orbital to create a new type of orbital when one S orbital combines with two P orbitals, it looks like this two P orbitals when these three combine you get an sp2 hybrid when one S orbital combines with one p orbital it looks like this here is an S orbital here is a p orbital you get a SP hybrid and covalently bonded hybrid orbitals will overlap with other types of orbitals to pair unpaired electrons, furthermore, electrons that are paired and shared give nonmetals an octet which is a higher form of stability.

Carbon will hybridize its orbitals in the second energy levels to form sp3 hybrid orbitals, so here is the normal configuration of carbon with a single electron. and one S orbital and three electrons and the P orbitals, if we combine the s and P orbitals all together we get an sp3 hybrid, so each electron now does not occupy an S orbital or a p orbital, but each electron occupies an sp3 hybrid and below there is a diagram showing how the S orbitals of four hydrogens overlap the sp3 orbitals of carbon to form covalent bonds and note that each observes that carbon has one octet, so the S orbital of hydrogen overlaps the hybrid orbital of carbon and this pairs unpaired electrons and that makes the atoms happy or that makes a hydrogen happy, now it has two electrons and then as each hydrogen overlaps the orbitals, now the carbon has 2 4 6 8 electrons around it an octet, so that makes it happy and below is a diagram showing how 2 carbons and six hydrogens will overlap their orbitals to form c2h6.

Note again that carbon has an octet, so instead of one hybrid orbital overlapping the S orbital of hydrogen, only these two hybrid orbitals will overlap each other and we will have a single bond between hydrogen and carbon at any time. . two electrons between two atoms that will be a single bond, so the two electrons directly in the middle are a single boss, we have a single bond between the hydrogen and the carbon, we have a single bond between the carbons, two electrons between the atoms, that It is a single bond, two carbons and four hydrogens can form covalent bonds and for this to occur each carbon will have to hybridize its SP orbitals to an sp2 configuration, so each carbon when this occurs will now have three sp2 hybrid orbitals and a single p orbital. , so the S orbital will combine with 2p orbitals and format the sp2 hybrid so that each electron here occupies an sp2 hybrid and leave only the p orbital with a single electron.

Now the P orbitals on both carbons will be oriented next to each other and this allows the top of one p orbital to overlap the top of the other p orbital the bottom half of each p orbital will also overlap each other overlapping the p orbitals this way produces a crescent shape up and down so here we have two carbon atoms and each carbon atom is going to have a lone p orbital with an electron in it, so this p orbital here represents is represented right here , so that's the p orbital of one carbon and this is the p orbital of another carbon atom and what is it?

What will happen is that when the two carbon atoms move together, the p orbitals will overlap and when this happens, these up and down crescent shapes will form, so let's see what it looks like when we have two carbons moving close together. Alright, below is a diagram showing how the P orbitals and hybrid orbitals of carbon overlap to form two c2h4s. The P orbitals are colored pink. Now the diagram shows two types of links. Sigma bonds and pi bonds in a sigma bond, the shared electrons are directly between the Atoms, the diagram also shows single bonds between two carbons and there are also Sigma bonds between the carbons and the Sigma bonds of hydrogen are the result of a direct superposition between orbitals.

A single bond between atoms is a sigma bond, so here we have a sigma bond. okay so the electrons are right in the middle here we have a sigma bond right here these electrons are right between a sigma bond here so twice the c bond we have a sigma bond sigma bond okay so that's the first type of bond now A PI bond is a covalent bond where the shared electrons are not directly between the atoms, the lateral overlap between the P orbitals creates a PI bond, so when these P orbitals between the two carbons overlap like they do in this image hence, these P orbitals overlap. it will form a sort of crescent shape, remember what the crescent shape is right there, so this side overlap creates this crescent shape and we have a PI link.

Now notice that these electrons here are not directly between the carbons, these electrons in this image. they are above the plane, so any time you have shared electrons that are not directly between them, that is called a PI bond. If we look at this image, we have to give two covalent bonds between the carbons and when this happens we have a double bond. bond a double bond is made up of a Sigma bond and a PI bond, so here is a covalent bond, it is a sigma bond because these electrons are directly in the middle, here is the other covalent bond in pink, these electrons are above of the plane of the carbons in which they are not directly between this is a PI bond Sigma bond PI bond you get a double bond, so what double bond is made of a Sigma bond and a PI bond?

Let's make another type of molecule, two carbons and two hydrogens can join together to form. c2h2 and for this to happen, each carbon will hybridize its orbitals to form an SP hybrid and this will give us two SP orbitals and two P orbitals, so for a carbon we take an S orbital and then a single P in general to form a SP hybrid and that leaves these two electrons left over, so we're going to take two carbons and each carbon will have two SP orbitals and two lone P orbitals. So each carbon has two SP orbitals, two P orbitals and it will look like this So this is a model that represents something like what I'm trying to show in this image here, these orbitals here I represent with the white loops here, like this that there would be an electron here and there would be an electron right here. here and then one of these lines is a p orbital, so the red loops here represent an up and down p orbital and then the other line represents another p orbital, that's the green loop here, okay, so we have a S orbital, don't do SP. hybrid here that's this white loop an SP orbital right there that's this other loop here we have a p orbital right here which could be represented by the red loops and then we have another p orbital right here which is the green loops so we have orbitals from left to right, up and down and then front and back, so the green represents the P orbitals coming towards you, front and back, so here is another image of a carbon and what we are going to show is that I can orient them correctly there. everything is going well, so what we are going to do is have the two carbons move together so that their orbitals overlap, then what will happen is that the carbons will move closer to each other and then the SP orbitals will overlap. with each other and share electrons and then they will get close enough that the P orbitals also overlap the upper red P orbitals overlap here on the top and bottom so the red orbitals overlap on the top and bottom and they will also get close enough. so that the green P orbitals overlap in front and behind, then there will be two types of overlap, an overlap between s and P s here, there will be an overlap between the vertical P orbitals in the red top and bottom and then there will be an overlap between the green P orbitals in front and behind so I hope these little diagrams make it clearer the SP overlap between the white ones p orbital overlap between the green ones p orbital overlap between the red ones okay so this is c2h2 this is what The c2h2 molecule is ve with a triple bond in the middle so this diagram shows how the P orbitals and the hybrid orbitals of carbon overlap to form c2h2 so one p orbital is pink and the other p orbital is green like this , so we have our red or pink and then we have our green, that's what this is trying to represent right now.

If you look at this image, there are three covalent bonds between the carbons and this is called a triple bond. A triple bond is formed by a sigma bond. For the pi bonds, the pi bonds are formed by the lateral overlap of the P orbitals, so when these two come together we have the Sigma bond here, so this Sigma bond is the overlap between the white orbitals, all good, that is represented here and then. when these pink orbitals on pink, the P orbitals overlap on the top and bottom, you get these crescents here, and then when the green orbitals overlap front and back, you get these crescents here, so I am going to repeat that there are three covalent bonds. between the carbons it is a triple when you have three covalent bonds it is a triple bond the triple bond is made of a sigma bond and to buy bonds a PI bond up and down in pink or red the other PI bond in green in front and back so that The P orbitals overlap top and bottom in pink and front and back in green.

Alright, a triple bond is made of one Sigma bond and two pi bonds and pink and green. Okay, for a PDF transcript of this conference, visit wwe.com. This has been the 37th chemistry conference covalent bond