In the molecule of ethene C2H4 , the carbon atoms form sp2 hybrid orbitals. Each carbon atom is bonded to three other atoms: two hydrogen atoms and one other carbon atom. The sp2 hybridization involves the mixing of one s orbital and two p orbitals to form three sp2 hybrid orbitals. These orbitals form sigma bonds with the hydrogen atoms and the other carbon atom, while a pi bond is formed between the two carbon atoms due to the overlap of their unhybridized p orbitals.