Internuclear Axis:
A straight line that goes through the nuclei of two bonding atoms

Sigma Bond:
When atoms overlap ON the internuclear axis
Creates a sausage shape between the atom circles
For p-orbitals, the phases/colors HAVE to be the same.

ALL single covalent bonds ARE sigma bonds
Two “s” orbitals overlap
One “p” orbital lobe overlaps with one “s” orbital
Two “p” orbital lobes overlapping

Single Bond:
One sigma bond

Double Bond:
One sigma bond AND one pi bond

Triple Bond:
One sigma bond AND two pi bonds

Pi bond:
When atoms overlap PERPENDICULAR to the internuclear axis, side by side.
They create a NODE
The overlap is LESS than sigma bonds, so they are WEAKER.
They happen AFTER the first sigma bond, never before.