If a piece of graphite is connected into a circuit, electrons can fall off one end of the sheet and be replaced with new ones at the other end.
Carbon element drawing free#
The delocalized electrons are free to move throughout the sheets. Attractions between solvent molecules and carbon atoms will never be strong enough to overcome the strong covalent bonds in graphite. Graphite is insoluble in water and organic solvents - for the same reason that diamond is insoluble. This is because of the relatively large amount of space that is "wasted" between the sheets. Graphite has a lower density than diamond. When you use a pencil, sheets are rubbed off and stick to the paper. You can think of graphite rather like a pack of cards - each card is strong, but the cards will slide over each other, or even fall off the pack altogether. It has a soft, slippery feel, and is used in pencils and as a dry lubricant for things like locks. You have to break the covalent bonding throughout the whole structure. In order to melt graphite, it isn't enough to loosen one sheet from another. Graphite has a high melting point, similar to that of diamond. As the delocalized electrons move around in the sheet, very large temporary dipoles can be set up which will induce opposite dipoles in the sheets above and below - and so on throughout the whole graphite crystal. So what holds the sheets together? In graphite you have the ultimate example of van der Waals dispersion forces. The atoms within a sheet are held together by strong covalent bonds - stronger, in fact, than in diamond because of the additional bonding caused by the delocalized electrons. There is, however, no direct contact between the delocalized electrons in one sheet and those in the neighboring sheets. The important thing is that the delocalized electrons are free to move anywhere within the sheet - each electron is no longer fixed to a particular carbon atom. They are no longer associated directly with any particular atom or pair of atoms, but are free to wander throughout the whole sheet. These "spare" electrons in each carbon atom become delocalized over the whole of the sheet of atoms in one layer. That leaves a fourth electron in the bonding level. \)Įach carbon atom uses three of its electrons to form simple bonds to its three close neighbors.
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