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# How do you count sigma and pi bonds?

To count sigma and , first you need to know how many single, double and triple bonds are present in the molecule.

A single bond contains one sigma bond (direct head-on overlap of orbitals).

For example, the "C-C" sigma bond in ethane is formed by the head-on overlap of two sp^3 orbitals. The C-H sigma bonds are formed by s"-"sp^3 overlap.

A double bond contains one sigma bond and one pi bond (side-on overlap of p orbitals).

In ethylene, the "C=C" double bond consists of a sigma bond and a pi bond. The sigma bond is formed by the head-on overlap of two sp^2 orbitals. The pi bond is formed by the side-on overlap of two 2p orbitals.

A triple bond contains one sigma bond and 2 pi bonds.

In acetylene, the "C≡C" triple bond consists of a sigma bond and two pi bonds. The sigma bond is formed by the head-on overlap of two sp orbitals. The pi bonds are formed by the side-on overlap of 2p orbitals.

It's just that simple.

Here's a video on counting sigma and pi bonds.