Describe sp3 hybridisation

Eg: carbon atom 2s2 and 2p2 an electron from the 2s sub level is promoted to an empty orbital in the 2p sub level = excited state (1 e in 2s and 3 in 2p) The 2s and 2p orbitals mix to form sp3 hybrid orbitals = degenerate same energy explains why carbon can form 4 bonds