While studying chemical bonding for methane,ethyne etc., I have made the following assumption to help me to remember the sigma bond, pai bond, and hybrid orbitals. 1. Every single covalent bond around a carbon atom is a sigma bond. 2. Only one of the bond in double and triple covalent bond is a sigma bond. The others are pai bond. 3. If there are 4 sigma bond around a single carbon atom, sp^3 hybid orbitals are involved. Is my assumption wrong? Or they are just suitable for certain hyddrocarbon?