Why does ethene not conduct electricity?
The flow of electrons result in electricity and
Only those things conduct electricity in which free electrons
Free electron means that the electron is not bonded to any atom or ion and thus it can easily move under the influence of Electric or magnetic field, so it can conduct electricity.
In Ethene there are no free electrons, because in the Covalent bonds of the atoms in Ethene, the elecrons have taken part in bonding and are not freely available so it does not conduct electricity.
While in metals , semiconductors or aqueous solutions of Strong electrolytes conduct electricity due to availablity of free electrons and ions(charges) in case of Electrolytes.
In case of Graphite, it is explained in the pic given below :-
In Graphite, the electrons which form the 'pi' bond are freely available, and thus conduct electricity because in graphite the hexagonal layers form sheet of planar carbon atoms; thus atoms are joined to each other and can conduct electricity.
BUT, the Ethene exists as discrete molecule, not as a sheet of carbon atoms arranged in a plane, also not as a chain of carbon atoms, thus it cannot conduct electricity because the electron in the 'pi' bond of ethene cannot travel between different carbon atoms (other than the 2 carbon atoms present in that single ethene molecule) because of the unavailability of the structure needed for the conduction of electricity (ie Planar molecule or having chain of atoms)