<P> With 133 pm, the ethylene C = C bond length is shorter than the C − C length in ethane with 154 pm . The double bond is also stronger, 636 kJ mol versus 368 kJ mol but not twice as much as the pi - bond is weaker than the sigma bond due to less effective pi - overlap . </P> <P> In an alternative representation, the double bond results from two overlapping sp orbitals as in a bent bond . </P> <Table> <Tr> <Th> </Th> <Th> </Th> <Th> O </Th> <Th> </Th> <Th> </Th> </Tr> <Tr> <Th> </Th> <Td> alkene </Td> <Td> carbonyl group </Td> <Td> imine </Td> <Td> thioketone, thial </Td> </Tr> <Tr> <Th> O </Th> <Td> </Td> <Td> dioxygen </Td> <Td> nitroso compound </Td> <Td> sulfoxide, sulfone, sulfinic acid, sulfonic acid </Td> </Tr> <Tr> <Th> </Th> <Td> </Td> <Td> </Td> <Td> azo compound </Td> <Td> </Td> </Tr> <Tr> <Th> </Th> <Td> </Td> <Td> </Td> <Td> </Td> <Td> disulfur </Td> </Tr> </Table> <Tr> <Th> </Th> <Th> </Th> <Th> O </Th> <Th> </Th> <Th> </Th> </Tr>

When does a molecule have a double bond