it has been more than month since I wrote about chemical bonds. It was easy post just an explanation to all kinds of bonds: covalent, coordinate, ionic, two days back I updated it so there are even polar and nonpolar bonds but what I want to look on right now are sigma, pi and whole other kinds of bonds. This is a different perspective, it is more kind of from inside. Again like few other chemistry posts I made this because our teacher in school as I found out did not learn us what I would say is interesting and maybe important.
So from the last post we know that atoms that are bonded together are bonded in different ways, usually this is just dependent on the electronegativity, or if it is metal or not. But then you can look in these bonds and sort them in other groups:
σ is a sigma bond. This is the most basic kind. Bonds create when there is enough energy and the atoms are turned toward each other in right way. Always when there is bond, double or triple there will always be one sigma bond and it will be the first bond to create. This bond is also the strongest one. Sigma can form between s orbitals or two p orbitals or s and p or even two d’s. There are some more conditions about axis and so on but if you have a single bond between two atoms it always going to be sigma.
π is a pi bond. This is the second most common one and you can have more of them between two atoms. For example triple bond will be usually made up of one sigma and two pi bonds. They are not so strong, when you know this you know that when you will break them up, pi bonds will be the first ones destroyed.
Because pi bond looks like the one above, the orbitals do not overlap so much, the force is not so strong. Second picture shows where is probability cloud strongest. The combination of sigma and pi bond is actually very efficient since it contracts the length of the bond making it stronger.
δ is a delta bond. Actually I have never heard about this one before, but it is the bond that first appears when you have quadruple bond. This is very rare but some atoms can have even quintuple bonds between each other. When there is such a quadruple bond there is also one sigma bond and two pi bonds with delta bond. It creates by overlaping of two d orbitals, that is why it is called delta bond. Metals as rhenium, molybdenum or chromium can have such a bond.
On left you can see how this overlap should look like, this particular one is for two molybden atoms. But I can not really imagine how those look like really..
φ is a phy bond. This last one is kind of only for fun since we were able to observe it only between two uranium atoms because they need two f orbitals which are found only in really heavy elements which are usually either radioactive or made only by human and usually both.
On the right you can see two f orbitals that could touch each other and maybe create this crazy bond.
So how is this related to covalent bonds and so on again? You can sort bonds between atoms into groups. For example bond between two carbon atoms will always be covalent bond because there is 0 difference in their electronegativity. It does not matter if there are two or three bonds inside. Then you can look on them and sort them if they are sigma, pi or even delta bonds which depends on their orbitals.