Question

How do covalent bonds conduct electricity?

Answer 1

Sigma bonds conduct a small amount of electricity by quantum tunnelling, but delocalized pi bonds are good conductors of electricity..

Explanation:

SIGMA BONDS

Most chemists say that covalent bonds do not conduct electricity, because the electrons are trapped in the sigma bonds.

But a quantum mechanical effect called quantum tunnelling allows the electrons to tunnel through the energy barriers.

However, the effect is so small that compounds with only sigma bonds are extremely poor conductors.

For most purposes, we say that sigma bonds do not conduct electricity.

Can you spot the error in the bather's argument?

CONJUGATED π BONDS

Graphite

Graphite is a good conductor of electricity.

It consists of layered sheets of benzene rings all fused together.

http://rickwilsondmd.typepad.com/.a/6a01156e42deab970c0133f4de294b970b-pi

As in benzene, each carbon is `sp^2` hybridized and has an unhybridized `p` orbital.

In each layer of graphite, the `p` orbitals overlap to form a sheet of delocalized electrons.

(from slideplayer.com)

Hence, graphite can conduct electricity from one side of a sheet to the other.

Graphene

Graphene is a single sheet of graphite.

As with graphite, the π electrons are delocalized and free to roam from one edge to the other.

Carbon nanotubes

Carbon nanotubes are seamless cylindrical fibres made from a single sheet of graphene.

Their electron delocalization means electrical charge can move freely along a nanotube.