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Sigma and Pi Bonds


Simply put, a sigma bond is a single covalent bond.

The electron pair is located between the two atoms involved in the bonding.

A pi bond uses the p-orbitals that are located above and below these atoms.

The overlap is a pi-bond. The image above is actually only 1 pi-bond.

A p-orbital is has a shape of a dumbbell. So there are 2 regions of overlapping.

So, the grey bond is a sigma bond (a single bond), the clouds are a pi (this is the second bond or your double bond).

So, how can we have triple bonds? Use the image below

The region of space above and below the sigma bond (single bond) are already occupied. The p-orbitals (Pink) can wrap around to the left and right of the sigma bond. This overlap is 90o from the other pi-bond (blue) that is already in place. So it is possible to have 2-pi bonds and a sigma or what we call a triple bond.



In conclusion, a triple bond is a sigma bond located directly between the atoms, and 2 pi bonds located above and below, and around the sides of the 2 atoms.

Every bond has a sigma. Doubles have a sigma and a pi. Triples have a sigma and two pi bonds.

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