Both a Sigma and Pi Bond between Orbitals

[Chiara Frank]

Hey guys! I have been reviewing the previous lectures, and while discussing hybridization in lectures 19 and 20, Dr. Lavelle explained how there is both a pi and sigma bond where the orbitals overlap. An example he used was Ethene (or Ethylene), C2H4. He drew the overlapping orbitals between the two C atoms, and thus the pi and sigma bond. I believe he said that where the p orbitals overlap is where we get the pi bond. I understand that the double bond means a sigma plus a pi bond, but are we able to derive this just from the lewis structure or do we need to also draw the overlapping of the p orbitals? Or are the orbitals just a further explanation of why we have these two bonds? Thank you!

[405669838]

I believe we can know this just from the lewis structure, but we also need to know that there are pi bonds if there is a hybrid orbital.

[Uma Patil 2A]

You are correct, the pi bond is what results when the unhybridized p orbitals overlap (from the sides). But, in order to identify pi bonds, you just need the lewis structure. There is no need to derive it by drawing out the hybridized and unhybridized orbitals of a compound.