Question

Explain the structure of graphite giving the reason for its softness as well as its electrical conductivity.

Answer 1

Good conductor of electricity : In graphite carbon atom is $$sp^2$$ hybridised. Out of four valiancy electrons in each carbon atom only three electrons, one fron $$2s$$ and two from $$2p$$ are involved in hybridisation. One spare electrons in its $$2p_z$$ orbital is left free. These $$2p_z$$ orbital overlap to form delocalies $$\pi$$ system which extends above and below each layer. In this delocalies $$\pi$$ electrons are free to move within the layer and hence graphite is a good conductor of electricity.

The conductivity of graphite perpendicular to the plane of the layers of hexagons is low and increases with increase in temperature, signifying that graphite is a semiconductor in that direction. The electrical conductivity is much higher parallel to the plane but decreases as the temperature is raised.

Soft, flaky and slippery substance : In graphite each layers of hexagon are held together by a weak Vander Waal's force of attraction at a large distance of $$3.40A^o$$. Even the slight pressure caused the layers to slide over one another. Hence graphite is soft, flaky and slippery. Graphite is used as a lubricant.