Chemistry · Ch 11 — The p-Block Elements
Graphite
Graphite
Graphite
Graphite has a layered structure built from planar hexagonal rings of carbon atoms (Fig. 11.4 shows the stacked hexagonal sheets). Successive layers are held together by only weak van der Waals forces and are separated by 340 pm; within a single layer, the C–C bond is much shorter, 141.5 pm.
Every carbon atom in the hexagonal sheet is hybridised, forming three bonds to its three neighbouring carbons within the plane. The fourth (leftover) electron on each carbon goes into a bond, and these electrons are delocalised across the entire sheet, free to move over it. This delocalisation is why graphite conducts electricity along the layers.
Because the layers themselves are held together only weakly, they slide over one another and cleave apart easily — this is why graphite feels soft and slippery, and why it is used as a dry (solid) lubricant in machinery running too hot for ordinary oil lubricants. …
What this figure shows. A diagram of stacked flat sheets, each sheet made of dark spheres (carbon atoms) joined by solid lines into a repeating hexagonal (honeycomb) lattice pattern lying in a horizontal plane. Several such hexagonal sheets are drawn one above another, connected between layers by vertical dashed lines showing the layers are stacked in register but not covalently bonded. A double-headed arrow on the left, labelled '340 pm', marks the spacing between two stacked layers, and a separate label '141.5 pm' at the top marks the sho …